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ABSTRACT

THE CEREAL LEAF BEETLE, Oulema melanopus (L.),
AND ITS INTERACTION WITH TWO PRIMARY
HOSTS: WINTER WHEAT AND SPRING OATS

 

BY

Stuart H. Cage

The biology and dynamics of the cereal leaf beetle is becoming
well documented but little is understood about the role of plant
dynamics in this beetle's life system. The objective of this study
was to quantify the interaction between the cereal leaf beetle and its
hosts within a season.

Field populations of the cereal leaf beetle, 'Genessee' wheat
and 'Clinton 64' oats were examined throughout a season to identify
the important plant and insect components which would assist in
quantifying this interaction.

The amount of leaf surface per unit area is a basic plant req-
uisite with respect to final grain yield and is important to the survival
of the cereal leaf beetle because it lays eggs and feeds on the suc-
culent upper leaf surface.

Two estimates of the amount of foliage removed from the cr0ps
by the insect population were made. First, the actual numbers of
feeding scars on the leaves were counted from samples taken throughout
the season and second, the larval population was translated into first

instar feeding equivalents by knowing how much each of the 4 instars

 

 

 

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resp.

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Stuart H. Gage
consumes during its life. The constants for converting a larval
population of known instar distribution are 1.0, 2.87, 5.97 and 24.23
respectively for the 4 instars. Knowing the amount a first instar
consumes, the population can be weighted accordingly.

Estimates of 45,647 and 73,035 sq. mm. per sq. ft. of foliage
were removed by 88.01 and 142.78 total larvae per sq. ft. respectively
in wheat and oats. Under the conditions investigated, winter wheat
surface area production was about 3.4 times that of oats at peak feeding
by cereal leaf beetle larvae. Oats received more damage than wheat but
this cannot be translated into yield loss.

It is suggested that the phase of defining the effect of the
beetle on yield be initiated over a broad geographical area within the

context of the 'cereal leaf beetle population dynamics survey'.

THE CEREAL LEAF BEETLE, Oulema melanopus (L.),

 

AND ITS INTERACTION WITH TWO PRIMARY
HOSTS: WINTER WHEAT AND SPRING OATS
By '3.

n.
.‘

Stuart Hquage

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE
Department of Entomology

1972

ACKNOWLEDGEMENTS

My sincere appreciation is extended to Dr. Dean L. Haynes under
whose direction this work was accomplished. I have had respect for his
scientific insight since we met at North Dakota State in 1966. His
advice and assistance led me to Fredericton, New Brunswick where I
worked on the Green River Project. Since coming to Michigan State to
work with Dr. Haynes, my respect has been enhanced.

I would also like to thank Dr. James Webster whose work in the
area of host plant resistance helped stimulate my interest in plants
and Dr. Robert Barr, of the Dept. of Electrical Engineering and Systems
Science, whose systems viewpoint has helped place the plant component
in its prOper perspective within the cereal leaf beetle management
system.

Dr. Stan Wellso and Dr. Fred Stehr had important input into my
program and their evaluations are appreciated. Dr. Gordon Guyer's
comments from the economic entomologist's standpoint helps to bring
entomology to real world situations.

Dr. Patricia Gage bravely withstood many hours while I thought
about 'leaves' and her patience and understanding was remarkable during

my transition from studying birds to studying plants.

TABLE OF CONTENTS

LIST OF TABLES . . . . . . . . . . . . . . . .

LIST OF FIGURES . . . . . . . . . . . . .

INTRODUCTION 0 O O O O O O O O O O O O I O O O O O

LITE MTURE REVIEW 0 O O O 0 O O O O O O O O O O 0
MATERIALS AND METHODS . . . . . . . . . . . . .

Study Areas . . . . . . . . . . . . . . .
Plant Sampling . . . . . . . . . . . .
Cereal Leaf Beetle Feeding Damage . .
Cereal Leaf Beetle Population Sampling
Degree-days . . . . . . . . . . . . . .

RESULTS 0 O O O O O O O O O O O O O O O O O

Vegetative Phase . . . . . . . . . . . . . . .
Cr0p Height . . . . . . . . . . . . . . . . . .
Head Component . . . . . . . . . . . . .
Root Biomass . . . . . . . . . . . . . . . .
Cereal Leaf Beetle Population Densities . . .
Foliage Consumption Estimated from Cereal Leaf
Beetle Population Densities . . . . . . . . .
Foliage Consumed by Estimates of Leaf Damage .

DISCIJSSION I O O O O O O O O O O O O O O O O O O 0

SUMMARY AND CONCLUSIONS . . . . . . . . . . . .

LITERATURE CITED . . . . . . . . . . . . . . .

APPENDICES . . . . . . . . . . . . . . . . . .

ii

Page
iii

vi

19

19
19
21
21
22

24
24
36
36
36
47

49
54

73
84
86

90

Table

LIST OF TABLES

Amount of feeding (mg.) on oat seedlings by larvae and
adults of the cereal leaf beetle based on 24-hour
tests (after Castro g£_§l, 1965) . . . . . . . . . .

Shoots per winter wheat plant at different stages of
growth sown at different densities (In Bunting and
Drennan 1966 after Puckeridge 1962) . . . . . . .

Accumulated heat units (base 48°F) for completion of
development of cereal leaf beetle eggs, larvae
and pupae . . . . . . . . . . . . . . . . . . . . .

Oven dry weight (g. per sq. ft.) of the top 3 leaves,
all leaves and the per cent of the total leaf weight
contributed by the tap 3 leaves in winter wheat
and spring oats at each sample date and corresponding
accumulated degree-days (base 42°F) . . . . . . .

Leaf lengths (mm.) of the top 3 leaves of winter wheat
and spring oats calculated from total leaf length per
leaf type per sample divided by the total number of
leaves per leaf type per sample at each sample date
and corresponding accumulated degree-days (base 42°F)
(n = 10; :_S.E.) . . . . . . . . . . . . . . . . . .

Leaf length (mm.) of the t0p three leaves of winter wheat
and spring oats determined from subsampling 5 leaves
of each type at each sample date and corresponding
accumulated degree-days (base 42°F) (n = 5; : S.E.) .

Flag leaf lengths (mm.) collected from fields of winter
wheat and spring oats at Gull Lake and East Lansing
(: SOB.) o o o o o o o o o o o o o o o o o o o o o 0

Per cent composition of each of the top 6 leaves of the
total number of the top 6 leaves in each sample of
winter wheat and spring oats at each sampling date
and corresponding accumulated degree—days (base 42°F)

iii

Page

11

23

28

31

32

33

34

Table

10.

ll.

12.

l3.

14.

15.

l6.

l7.

18.

Page

Number of plants, stems and stems per plant (per sq. ft.)
in winter wheat and spring oats at each sampling date
and corresponding accumulated degree-days (base 42°F)
(n a 10) . . . . . . . . . . . . . . . . . . . . . . . 3S

Calculated surface area (sq. mm. per sq. ft.) of the
top 3 leaves of winter wheat and spring oats at each
sampling date and corresponding accumulated degree-
days (base 42°F) (see text) . . . . . . . . . . . . . . 37

Regression equations to predict oven dry weight (g. per
linear ft.) from wet sample weight (g. per linear ft.)
for roots, stems, the top 4 leaves and heads of winter
wheat and spring oats sampled throughout the growing
season . . . . . . . . . . . . . . . . . . . . . . . . 43

Per cent moisture remaining in the roots, stems and the
top 4 leaves at each sample date and corresponding
degree-days (base 42°F) (n = 10) . . . . . . . . . . . 44

Within field comparison of plant height (cm.) total
wet sample weight (g.), oven dry weight of heads
(g.) and number of heads in spring oats (n = 3;
:_S.E.) . . . . . . . . . . . . . . . . . . . . . . . . 45

Within field comparison of plant height (cm.), total
wet sample weight (g.), oven dry weight of heads (g.)
and number of heads in winter wheat (n = 3; :_S.E.) . . 46

Amount of foliage consumed by each instar of the
cereal leaf beetle and the corresponding first
instar feeding equivalent conversion (see text) . . . . 49

Cumulative first instar feeding equivalents and the
cumulative estimate of foliage consumed (sq. mm.
per sq. ft.) from winter wheat and spring oats as
determined from first instar feeding equivalent
incidence curves . . . . . . . . . . . . . . . . . . . 52

Number of feeding scars per leaf on each of the top
3 leaves and the corresponding average scar area
(sq. mm.) in winter wheat and spring oats at each
sample date and corresponding accumulated degree-
days (base 48°F) . . . . . . . . . . . . . . . . . . . 55

Cumulative amount of foliage consumed (sq. mm. per

sq. ft.) from the top 3 leaves of winter wheat and
spring oats . . . . . . . . . . . . . . . . . . . . . . 56

iv

Table

19.

20.

21.

22.

23.

24.

25.

26.

27.

28.

29.

30.

Final amount of foliage (sq. mm.) consumed by cereal
leaf beetles as predicted by the 2 methods (see
text) 0 O O O O O O O I O O O O O O O C C O O O O O O 0

Per cent utilization of the top 3 leaves of winter
wheat and spring oats by the cereal leaf beetle . . .

Per cent of available leaf surface removed from the
top 3 leaves of winter wheat and spring oats by
the cereal leaf beetle as determined from damage
estimates . . . . . . . . . . . . . . . . . . . . . . .

Total biomass of foliage (g. per sq. ft.) present in
3 areas at peak cereal leaf beetle larval feeding .

Total monthly rainfall (in.) for May, June, and July
at Gull Lake and East Lansing . . . . . . . . . . . .

Accumulated degree-days from January 1 to July 31 at
base 42°F for Gull Lake and East Lansing . . . . . .

Total amount of foliage consumed (sq. mm. per sq. ft.)
calculated from cereal leaf beetle population
estimates converted to first instar feeding equivalents
in winter wheat and spring oats at Gull Lake and
East Lansing . . . . . . . . . . . . . . . . . . . . .

Prediction of larval survival and mortality and
generation survival and mortality from the within-
generation cereal leaf beetle model developed by
Helgesen and Haynes (in press) . . . . . . . .

Observations on egg laying behavior of the cereal leaf
beetle on oat seedlings in the laboratory (after
Castro g£_al, 1965) . . . . . . . . . . . . . . . . .

Crop growth rate of winter wheat (g. per degree-day
(base 42°F)) per sq. ft. at Gull Lake and
East Lansing . . . . . . . . . . . . . . . . . . . . .

Crop growth rate of spring oats (g. per degree-day
(base 42°F) per sq. ft.) at Gull Lake and
East LanSing O O O I O O C C O O O O O C O O O O O 0

Grain yields (bu. per acre) of 'Chancellor' wheat
and 'Arkwin' oats for 5 levels of leaf area
removal at 4 stages of plant develOpment (after
Womack and Thurman 1962) . . . . . . . . . . . . .

Page

58

59

6O

7O

7O

70

71

72

74

76

77

81

Figure

10.

11.

LIST OF FIGURES

Relationship between date and the number of shoots
per plant in winter wheat (adapted from Bunting
and Drennan 1966) . . . . . . . . . . . . . . . .

Relationship between accumulated degree-days (base
42°F) and oven dry weight of plant material above
ground in winter wheat and spring oats . . . . .

Relationship between accumulated degree-days (base
42°F) and oven dry weight of the top 3 leaves of
winter wheat and spring oats . . . . . . . . .

Relationship between leaf length and leaf surface
area in winter wheat . . . . . . . . . .

Relationship between leaf length and leaf surface
area in spring oats . . . . . . . . . . . . . .

Relationship between accumulated degree-days (base
42°F) and average plant height of winter wheat
and spring oats . . . . . . . . . . . . . . . .

Relationship between accumulated degree—days (base
42°F) and oven dry weight of heads of winter wheat
and spring oats . . . . . . . . . . . . . . .

Relationship between accumulated degree-days (base
42°F) and the number of heads of winter wheat
and spring oats . . . . . . . . . . . . . .

Relationship between wet sample weight and oven dry
weight of Spring oats . . . . . . . . . . . . .

Relationship between oven dry weight of winter wheat
and spring oat leaves and leaf surface area .

Relationship between accumulated degree-days (base
48°F), cereal leaf beetle larvae (O) and first
instar equivalents (0) on winter wheat and
spring oats . . . . . . . . .

vi

Page

12

25

27

29

30

38

39

40

42

48

51

Figure Page

12. Relationship between accumulated degree—days (base
48° F) and the predicted amount of foliage consumed
by cereal leaf beetle larval pOpulations on winter
wheat and spring oats using the first instar
equivalent method . . . . . . . . . . . . . . . . . . . 53

13. Relationship between accumulated degree-days (base
48°F) and the amount of foliage consumed by
populations of the cereal leaf beetle on winter
wheat and spring oats estimated from damage to
the top 3 leaves . . . . . . . . . . . . . . . . . . . 57

14. Relationship between accumulated days from April 20,
first instar feeding equivalents on winter
wheat and spring oats and:

(a) plant height . . . . . . . . . . . . . . . . . . . 62
(b) oven dry weight of leaves . . . . . . . . . . . . 63
(c) sum of the squares of the lengths of the

top 3 leaves . . . . . . . . . . . . . . . . . . . 64
(d) the number of heads . . . . . . . . . . . . . . . . 65

15. Relationship between accumulated days from April 20,
first instar feeding equivalents and oven dry
weight of foliage above ground for winter wheat
and spring oats at:

(a) Gull Lake - R area . . . . . . . . . . . . . . . . 67
(b) Gull Lake - T area . . . . . . . . . . . . . . . . 68
(c) East Lansing - C area . . . . . . . . . . . . . . . 69

16. Relationship between accumulated days from April 20,
first instar feeding equivalents and per cent
moisture in the tap 3 leaves of winter wheat and
Spring oats . . . . . . . . . . . . . . . . . . . . . . 79

vii

 

 

 

 

£1 E?
E
..4‘ f

INTRODUCTION

The cereal leaf beetle, Oulema melanopus (L.), is potentially

 

the most important insect pest of small grains in North America.
Damaging populations of this insect have occurred in southern Michigan
since 1959, after being introduced from EurOpe (Castro gt a1. 1965).

As of 1971 cereal leaf beetle populations were detected as far south

as Kentucky, north to Ottawa, Ontario, west to the Iowa border and east
of Michigan to the Atlantic coast (USDA Detection and Quarantine Survey
1971).

The cereal leaf beetle is not considered an economically impor-
tant pest of small grains throughout its range in the Old World. How-
ever, in the region of the Balkans, the Ukraine, and the Transcaucasia
area of the Soviet Union, Castro 35 31. (1965) noted that this pest
does more damage and is more constant in appearance. Miczulski (1971)
studied the cereal leaf beetle in Poland from 1966 to 1971 and found
that the amount of damage was non-economic and insignificant when com—
pared with what he observed in Yugoslavia in 1967.

In southern Michigan insecticide use has been necessary to pro—
tect the spring oat crop from the cereal leaf beetle. In 1969 and
1970, 1.41 x 105 and 1.78 x 105 acres of oats, respectively were sprayed
with malathion and carbaryl and unknown acreages were also sprayed with
azinphosmethyl in each of these years (Ruppel personal communication).

1

2

The within-generation population dynamics of the cereal leaf
beetle has been investigated (Helgesen and Haynes in press). Their
model shows that two major factors account for over half of the varia-
tion in within-generation mortality: the cereal leaf beetle popula-
tion level and host crop.

The principle economically important host plants of larvae and
adults of the cereal leaf beetle in North America are the small grains
(wheat, oats, barley and rye). This report will examine two of these
crops, winter wheat and spring oats, the two small grains most impor-
tant to Michigan agriculture.

The assumption underlying this investigation was that the host
crops contain specific dynamic components which directly influence the
cereal leaf beetle. Because the hosts of the beetle are equally as
dynamic as the consumer, the plant component became the central theme
of this study toward further understanding the pOpulation dynamics of
the cereal leaf beetle. By modeling the insect's interaction with its
primary cereal grain hosts, winter wheat and spring oats, it was hoped
that relationships would be uncovered which would aid in controlling
this pest.

To date little detailed published information is available con-
cerning the relationship of cereal leaf beetle populations to natural
growing cereal grains throughout a single season. Some significant
work has been published relative to cereal leaf beetle feeding on
plants (primarily seedlings grown in the laboratory) with regard to
adult survival (Wilson and Shade 1964) and host plant resistance
(Schillinger 1969, Webster and Smith 1971). Gallun £5 31. (1966)

studied host plant resistance under field conditions using damage ratings.

3
In this study three principle factors were investigated: (1)
the growth responses of winter wheat and spring oats, (2) the cereal
leaf beetle population density in each crOp and (3) adult and larval
feeding damage on each crap. Limited comparisons were made between

areas and within fields.

LITERATURE REVIEW

The bionomics of the cereal leaf beetle have been adequately
described by Castro gt 31. (1965) and Wellso et 31. (1970) have pub-
lished a comprehensive bibliography of literature pertaining to this
cereal grain pest.

The consumer-host interaction considered in this study initiates
when spring adults move from their overwintering sites into winter
wheat and begin feeding and laying eggs on the upper surface of the
leaves. Winter wheat, having established roots the previous autumn,
is one of the most abundant food sources for the adult beetles during
the latter part of April and early May, although several other hosts
become available later in the spring. When spring oats become avail-
able, numbers of adults appear in this crop. Ruesink (1972) suggests
that there is not much movement between winter wheat and spring oats
but that once in a crop, the beetles tend to remain there until death.
After the eggs hatch, the larvae immediately begin feeding adjacent
to the eggs on the leaf surface until the fourth instar larvae complete
development and pupates in the soil.

Helgesen and Haynes (in press) developed techniques for measuring
the within-generation population dynamics of the cereal leaf beetle
and developed a model which predicts within—generation survival from
cereal leaf beetle egg input. Their model is reiterated here to show
that survival of the first instar in oats and the fourth instar in

4

5

both wheat and oats varied predictably with density and host plant:

S I (oats) = l - (-.85 + .46 log x ), r = .78
3 IV (oats) = 1 — (-.18 + .28 log x ), r = .69
8 IV (Wheat)= l - (-.31 + .34 log x), r = .54

where x is the total number of eggs per sq. ft. Combining the constant
mortalities observed in the other life stages of the cereal leaf beetle,
Helgesen and Haynes (in press) simplified the within generation sur-
vival on the two crops to:

S W G (oats)

0.03914 (4.02174 - log x) (4.21429 - log x)

S W G (wheat) 0.04794 (3.85294 - log x).

Castro gt a1. (1965) discuss the relationships of the cereal
leaf beetle and its hosts. They noted that the cereal leaf beetle
preferred seedling plants and the younger growth of older plants and
that the beetles were more abundant in late planted winter grains than
in early planted winter grains. Table I (after Castro_e£-§l. 1965)
shows the amount of feeding by larvae and adults of the cereal leaf
beetle.

Wilson and Shade (1964) studied feeding by postdiapause adult
cereal leaf beetles in the laboratory and found that feeding choice
between wheat and rye and oats was not significant. They also noted
that survival was high on small grains but low on orchard grass, tall
fescue, millet, giant foxtail, grain sorgum and sudan grass.

Methods for determining the amount of foliage consumed by insects
have been developed for some Species and these methods (e.g. photometric,
radioactive tracers) have been applied by Crossley (1963) and Pegigo

39 31. (1970).

6

TABLE I.--Amounts of feeding (mg.) on oat seedlings by larvae and
adults of the cereal leaf beetle based on 24—hour tests
(after Castro £5 31. 1965)

 

Mg. of leaf consumed

 

Average wt.

 

of insect Per life
Stage Number (mg.) Per day (est)
lst instar larvae 10 0.22 2.14 5.35
2nd instar larvae 25 2.68 7.80 19.5
3rd instar larvae 10 7.80 12.9 41.7
4th instar larvae 15 20.8 26.4 52.8
Adults 41 7.35 25.9 1040.

 

Estimates of damage to plants caused by the cereal leaf beetle
are quite varied and without a reliable base for method comparison.
Castro et 31. (1965) rated damage from 0 to 5 based on visual estimates.
Wilson gt a1. (1969) took 20 stems at random from each plot and clas—
sified the leaves according to per cent that had been consumed (0,
trace, 10 to 100%), thereby using a rating of 12. Gallun_g£_al. (1966)
rated the damage visually from 1 to 5 with 1 being no feeding and 5
severe damage. Schillinger (1969) rated damage from 1 to 5 with 1
being highly resistant and 5 susceptible. Webster and Smith (1971)
also used the visual rating system but their system ranged from O to 3;
0 being no damage and 3 equal to heavy damage. In Poland (Miczulski
1971) estimated the per cent of surface area consumed by the cereal
leaf beetle and divided his classification as: less than 1%, l to 5%,

5 to 10%, 10 to 15%, 15 to 20% and more than 20%.

7

Larvae and adults feed almost entirely on the upper surfaces of
the leaves of their hosts and seldom feed on any other portion of the
plant. However, Merrit and Apple (1969) found that some feeding
occurred on the leaf sheath one inch beneath the base of the leaves
when the upper leaf surface was entirely consumed. Shade and Wilson
(1967) found that larvae feed only on the parenchyma tissue between the
leaf veins and noted that a larva feeds parallel to veins on favorable
hosts and perpendicular to veins on unfavorable hosts. They attributed
the reduced survival on some grasses to the leaf-vein spacing but
Helma (personal communication) noted that the data could be similarly
interpreted by attributing mortality differences to cool weather and
warm weather grasses which have different biochemical pathways.

Wilson 35 31. (1969) showed that only larger larval instars con-
sumed appreciable amounts of foliage on oats and that one larva, com-
pleting development to pupation, consumed about 20% of the leaf tissue
on one stem regardless of the vigor of the plant.

Yield loss on 'Monon' wheat caused by this insect was investi-
gated by Gallun gt a1. (1967) who found that up to 23% loss (kernal
number and size reduction) could be attributed to the cereal leaf
beetle but that such high losses would seldom occur in North America
where winter wheat is grown. Wilson gt 31. (1969) studied yield loss
in oats under field conditions. They noted that the degree of yield
loss depended on the stage of develOpment of the crop and that these
losses ranged from 2.29 to 4.1 bushels per acre per larva per stem.
Merrit and Apple (1969) also examined yield loss in oats and found a

grain yield reduction of 48.8%, or 4.77% per larva per stem for each

8
of the 10.4 larvae per stem. They also note that loss in straw weight
caused by the cereal leaf beetle was considerable. Womack and Thurman
(1962) studied the effect of leaf removal in 'Chancellor' winter wheat
and 'Arkwin' winter oats by removing 10%, 20%, 30%, 40% and no leaf
removal at 1 week before the boot stage, at the boot stage, 1 week after
the boot stage and 2 weeks after the boot stage. In wheat they found
that 1 week before the boot stage was the most critical stage and that
leaf area removal in excess of 10% was necessary to cause significant
reductions in yield. The stages of leaf area removal in oats had little
expressed effect on yield and that the 30 and 40% leaf removal treat-
ments reduced yields significantly below the check. In general, Womack
and Thurman (1962) conclude that reductions in grain yield due to leaf
removal were primarily a result of reduction in seed size.

Blackman (1959) appraised 4 decades of research in plant growth
and plant responses to environmental factors. He expressed anxiety
that he had made no reference to American workers and stated:

This omission is not perverse but due to my inability to trace a
body of papers where the techniques of growth analysis have been
fully exploited. This divergence of interest I have discussed
on previous visits to the United States, and the opinion has
been expressed that the concepts are crude and yield but meager
information concerning the basic physiological processes that
determine the reaction of plants to the environmental factors.
My reply has been that it is essential to match what is learned
in the laboratory with an equal and precise knowledge of the
reactions of the plant as a whole for a wide range of species
and conditions. My hope is that this paper is persuasive

enough to support my contention that there is a continuum be-
tween research involving the cold room and centrifuge and field
experimentation seeking to assess plant performance.

The vegetative phase in cereals is taken to begin when the first

leaves appear above the soil and to end when the flag leaf has died

(Bunting and Drennan 1966). The leaf number attained prior to flowering

9
is not fixed and in field crops of wheat, barley and oats the total
number of leaves formed on the main shoot of the plant is usually from
7 to 9. At spring temperatures, the plastochron (the interval between
the appearance of successive primordia) in the temperate cereals is
2 to 3 days.

The flag leaf, the last to be formed on the shoot, may be deter—
mined no more than 15 to 20 days after germination or after growth of
autumn-sown craps starts in the spring. In wheat grown at 20°C, 6 new
leaves were initiated in 15 days after germination, in addition to the
3 leaves present in the embryo (Williams 1960 as seen in Bunting and
Drennan 1966). The latter authors note that in field crops, the
phyllochron (the time interval between successive leaf appearance) is
always considerably longer than the plastochron, often from 5 to 7
days, but increasing with time.

Other investigators studied plant components related to environ—
mental factors. Borrill (1959) showed that the curve obtained for the
length of successive leaves along the main shoot in the Gramineae
(Glyceria, Lolium and Triticum), was often of a definite shape, the
curve increased to a peak and then fell until the flag leaf appeared.
Leaf length trends were compared to Watson's (1947) trend in total leaf
area for wheat and barley and the trends were similar. Borrill (1959)
also noted that the behavior of autumn sown winter wheat revealed an
overall seasonal effect. This was indicated by the difference in the
general shape of the curve with respect to inflorescence initiation.
This was delayed beyond the peak of the curve, to the early part of a
second increase in leaf length associated with a decrease in the rate

of leaf production.

10

Jewiss (1966) notes that the number of visible living leaves on
a grass tiller is a direct result of the rate of leaf appearance and
the length of life of these leaves. Ryle (1964 reported in Jewiss
1966) has shown that the number of living leaves on the main stem may
vary between 3 and 6 according to genotype and environment.

Allison and Watson (1966) studied the production and distribu—
tion of dry matter in maize after flowering and noted that the leaf
laminae are the chief source of the dry matter in the grain of maize.
This contrasts with wheat and barley, in which laminae, sheath, and
ear all make substantial contributions to the dry matter in the grain.
Also, they noted that photosynthesis throughout the upper two-thirds
of the leaf area of maize supplied the dry matter that fills the grain,
whereas in wheat and barley the structures above the highest node
supply most of the dry matter. They attribute this difference to the
slower senescence of maize leaves with the lower leaves providing a
much larger preportion of the total photosynthetic area after ear
emergence than in wheat or barley. Finally, they note that dry matter
in the grain of maize, as contrasted with wheat or barley, comes mostly
from photosynthesis after flowering.

Ryle (1966) pointed out that the first component of final yield
in grasses is the number of fertile tillers per unit area. In sub-
sequent weeks, ear development proceeds until shortly before ear emer-
gence. During this time the second component of yield, the number of
florets per ear, is fixed followed by anthesis, pollination and fer-
tilization. This determines the third component of yield, seed set.
Finally the seeds swell and mature to determine the fourth and last

component, seed weight.

ll

Tillering is important during the vegetative stage and there
seems to be a characteristic trend of shoot numbers, especially in
wheat as pointed out by Bunting and Drennan (1966) by illustrating
Kirinde's (unpublished) figure (Figure 1).

Friend (1965) studied the effect of temperature and light in-
tensity on tillering and leaf production in wheat to determine the
importance of tillering. His studies constitute an essential addition
to plant growth studies conducted in North America, especially with
respect to the effect of environmental components on plant growth
(Friend 1966).

Puckeridge (1962) as seen in Bunting and Drennan (1966) recorded
in detail the effect of density on the growth of wheat sown at a range
of densities from 5.7 to 3,540 x 103 plants per acre (Table II).

TABLE II.—-Shoots per winter wheat plant at different stages of growth

sown at different densities (In Bunting and Drennan 1966
after Puckridge 1962)

 

 

-_.-__-..-_.-—_-_- _-__—__._..._._- -.....— -

 

 

 

Shoots/Plant
Initial density Weeks from sowingg(23 May 1961)

x 103 plants/acre 4 10 14 17 20 26
5.7 1.8 16.4 24.9 40.5 37.0 33.0

28.3 1.9 16.1 30.0 29.5 27.0 24.5

141.3 1.8 13.7 11.9 10.6 9.5 9.9
708.2* 2.0 5.5 4.1 3.0 3.0 3.3
3,541.0* 1.3 1.6 1.4 1.2 1.5 1.2

 

*At these densities the populations had fallen to 623.2 and
1,808.9 thousands, respectively, by week 26.

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13
Table II shows clearly that competition between plants affected
tiller numbers per plant. There must also have been competition be-
tween parts within individual plants, since the number of shoots per
plant declined from a maximum (even at the widest spacing) where the
number of tillers per acre was far lower than at the denser spacings
(Bunting and Drennan 1966).
The yield of cereal grains depends on a great many factors over
which man has little control. However, Watson (1956) considers several
influences on yield of crops and concludes that,
. . . the main opportunity for increasing yield lies in the
increase of leaf area. Information on the physiological cause
of variation in yield is still scanty, but, so far as it goes,
it indicates that cultural practices that increase yield do
so wholly or mainly by influencing leaf growth.

Later in the same paper Watson (1956) continues his argument by saying,

. . the conditions favoring high yield of grain in so far as

it depends on leaf area, appear to be: a high leaf area index
at the time of ear emergence, slow senescence of the leaves
then surviving, which implies a long time interval between
emergence and harvest. The fulfilment of these conditions
practically depends on the size and longevity of the flag leaf.

This explanation has been challenged by Gregory (1956) who
argues that the increase in leaf area depends on additional production
of tillers because early nitrogen application increases the rate of
tillering and therefore the rate of increase in leaf surface area in—
creased. This increase does not go on indefinitely because when flower
initiation occurs in the early tillers, then tillering stops. Rather
than emphasizing the flag leaf, Gregory (1956) emphasized the importance
of the emerging ear and the dependence of yield on the number of ears,

and also the fact that late applications of nitrogen produces tillers

that do not ear, therefore wasting nitrogen.

14

As Ryle (1966) noted, the number of fertile tillers per unit
area is a significant factor in determining yield. Thorne (1966) re-
viewed the physiological aspects of grain yield in cereals and points
out that the economic yield in cereals consists of a particular portion
of the biological yield (total dry matter production usually with some
water) so it does not depend on the whole photosynthetic performance of
the crop. Leaves, sheathes and stems below the flag leaf node usually
contribute little, about 15% of the final grain weight and it is sug—
gested that ample leaf area after ear emergence is one of the most
important attributes likely to enhance grain yield (Thorne 1966).

The analysis of plant growth under different environmental con-
ditions has had a long and somewhat confusing history; confusion due
primarily to problems in terminology. Blackman (1919) was one of the
first who was able to accurately quantify growth rates of plants by
applying the compound interest law to growth rates and analytical
techniques have been evolving since that time.

D. J. Watson of the Rothamsted Experimental Station in England
seems to have the most straight forward approach when dealing with the
growth rate of crOps under field conditions.

The total dry matter production by a crop may vary through a
change in either the size of the photosynthetic system or its activity,
as well as the length of the growth period during which photosynthesis
continues. These can be expressed as photosynthetic capacity and
photosynthetic efficiency (Watson 1958). The photosynthetic capacity
of crops is expressed by Watson as leaf area index (L, ratio of leaf
area to land area) while the photosynthetic efficiency is expressed as

net assimilation rate (E, rate of increase of dry matter per unity loaf

15

area). Watson's (1958) primary data consisted of initial and final
dry weights and leaf areas per plot of the plants harvested at the end
of the experimental period. The dry weights were expressed as yields
in g. per sq. m. and the leaf areas in sq. m. of land surface (i.e. leaf
area index).

Calculations of the growth functions in Watson's (1958) paper
were derived from the following formula:

(W2 — W1) (loge L2 - loge L1)

Mean net assimulation rate =
(t2 ’ ‘1) (L2 ‘ L1)

 

where W1, and W2 are initial and final total dry weight yields, L1 and

L2 the initial and final leaf area indices, and t1 and t2 the length of

the time interval. The mean rate of increase of dry weight yield in
g. per sq. m. of land area per unit time is:

w2 ‘ w1
t2 ' t1

Relative leaf growth rate per cent was calculated as

Crop growth rate (C) =

loge L2 - loge L

t2 ‘ t1

1

 

x 100.

Net assimulation rate calculations assume a linear relationship
between crop dry matter production (W) and leaf area index (L). To
deve10p a more general method of calculation. Whitehead and Meyerscough
(1962) used the exponential relationship

w = k L8 + c.

The exponent a is the ratio of the mean relative growth rate
(dry weight) to the mean relative growth rate in leaf area over a time
interval (t1 - t2). This may be calculated from

loge W - loge W

2 1
loge L2 - loge Ll

 

16
The mean net assimilation rate (E) may then be calculated for

a time interval t - t from the more general relationship

 

l 2
a - l a - l
E'= (W2 - W1) (L2 - L1 ) a
(1.28-1.13) <a-1)

Whitehead and Meyerscough (1962) present these formulas and
Williams 35 31. (1965) use them in their analysis of the growth rate
of corn describing additional uses of "a" for partitioning assimilates
within the plant. Similar arguments are followed by Evans and Hughes
(1962).

The growth of the plants and the final yield and quality of the
grain depend very materially on the weather conditions during the year
with light (radiation), moisture and temperature influencing the growth
rate of the plants. For this reason studies on the growth rates of
small grains have been conducted under controlled conditions to minimize
the effects of weather. Unfortunately few investigations have been con—
ducted under natural conditions because of variability caused by
existing light, temperature, wind and moisture condidons as well as
soil type, planting date and crOp variety.

Alcock 35 31. (1968) described an experiment designed to show
the effect of environment on the growth of a grass sward in 2 habitats
in North Wales. They noted that the growth of plants is very slow at
low temperatures but increases rapidly as temperature rises above a
certain minimum. Alcock_g£.§l. (1968) used the threshold temperature
of 5.5°C (42°F) for accumulating heat units (degree-days) and also used
the maximum soil temperature at 10 cm. The correlation of degree-days

above 42°F and maximum soil temperature at 10 cm. with yield (dry

l7
matter accumulation) showed a high positive coefficient. They note
that accumulation of heat above 42°F is highly correlated with time
which necessitated removal by using partial correlation. Doing this,
Alcock_gt.al. (1968) were able to explain 86% of the variation in
yield with these two variables. The soil temperature (at 10 cm.) was
found to be the most highly correlated variable with L (leaf area index)
accounting for 71 to 86% of the variation. They also found a significant
relationship between E (net assimilation rate) and radiation. Alcock
g£_al. (1968) note that the 10 cm. soil temperature is a complex factor
to interpret since, particularly in the spring, it is highly correlated
positively with radiation, grass minimum temperature, maximum air
temperature and negatively with wind speed, relative humidity, and
soil water content. The above authors suggest that wind speed may be
an important factor determining the habitat differences in soil tem—
perature and plant growth.

There has been some debate as to the usefulness of the concept
of heat accumulation above a certain threshold and Wang (1960) outlines
some of the problems involved. Its usefulness tends to outweigh the
disadvantages as long as the investigator realizes that the method is
not perfect because biological activity does not rely on temperature
alone.

The accumulation of heat units is a better prediction of varia-
tions in growth in spring than temperature itself (Mc Cloud, Bula and
Shaw 1964; Hogg 1965) or for that matter, date. Baskerville and Emin
(1969) present a means of rapid estimation of heat accumulation from
minimum and maximum temperatures assuming the sine curve as an approxi-

mation of the diurnal temperature curve. Van Den Brink gt a}, (1971)

 

‘W— —*W—_—‘r“ ’

‘fia-fi'

A

Mm,a. _‘.‘

note that 3
is perhaps
(1971) did
mean temper
temperatur.

used for a

 

18
note that plants respond to many meterological elements but temperature
is perhaps the most significant single factor. Van Den Brink g£_al.
(1971) did not use the sine curve approximation but simply took the
mean temperature ((max - mim) / 2) and subtracted this from several
temperature bases (40°F, 45°F, 50°F, 55°F) which they suggest can be

used for a range of crops.

 

VII-l!" 'lll l f. 'l‘llllt.‘ '[l

 

 

MATERIALS AND METHODS

Study Areas--Detailed studies of the plant growth of 'Genesee'
winter wheat and 'Clinton 64' spring oats and the interaction cereal
leaf beetles feeding on these two crops were conducted at Kellogg Gull
Lake Biological Research Station, Hickory Corners, Michigan in level
strip-planted fields 600 ft. x 50 ft., hereafter referred to as Gull
Lake - R. In other fields at Gull Lake, Gull Lake - T, about one-half
mile from Gull Lake - R and different in that the fields were on rolling
rather than level terrain, additional but limited measurements on
plant growth and beetle feeding were made at two elevations and com-
pared with observations from Gull Lake - R. Limited plant growth in—
formation (total biomass per sq. ft.) was also obtained from fields
near East Lansing, Michigan, hereafter referred to as East Lansing — C.

In each of these 3 areas detailed population estimates of the
beetle were obtained at about weekly intervals corresponding to the

plant growth measurements.

Plant Samplingé-Detailed plant growth measurements (Gull Lake - R)
were collected by random selection of 10 samples each a linear ft. in
length within each crop throughout the season. Plants were clipped
4 in. away from each end of a linear ft. row to avoid collecting addi—
tional stems. Each sample was then excavated by digging at an angle
down to include as much of the root component as possible from the

19

20
center of the plant rows (which were 7 in. apart). These samples, in-
cluding soil (extracted with the root systems) were placed in plastic
tubs and taken to the laboratory for processing. Water was placed in
the tubs and left standing overnight to allow the soil to loosen around
the root systems. The plants were then washed and separated according
to those stems which were connected by common root systems. These
were arbitrarily called plant combinations as they contained a variable
number of stems or tillers. The plant combinations were counted,
measured for height of the longest stem, weighed, wrapped in moist
paper toweling and placed in temporary storage at 44°F until processing
the next day. The samples were removed from storage, reweighed and
processed in the following manner. First, roots were clipped from
each plant combination, weighed and placed in labeled paper bags.
Second, stems were counted and recorded. Third, leaves were removed
from each stem at the ligule where the sheath separates from the stem.
Each leaf type was cut from every stem in each linear ft. sample and
placed in numbered trays. Leaves were numbered from the top down so
that the emerging leaves were placed in the first category (hereafter
referred to as type 1 leaves), the second leaves down the stem (type 2)
were placed in the second category, etc. Fourth, leaves were counted
and weighed by leaf type. Generally the earlier leaves (types 6 to 8)
were dessicated and these leaves were all placed in the sixth category.
Fifth, the leaves were laid out in linear rows by leaf type and the
number of individual leaves counted. The total length of each leaf
type in each sample was measured and then placed by type into labeled

paper bags. Sixth, roots, stems and heads (when present) were weighed

21

and placed in separate bags. Oven dry weight of each component was
obtained after drying the samples in a forced air drier at 105°C for
more than 24 hours.

Prior to drying the leaf type samples, 5 leaves of the first 4
leaf types were subsampled from each linear ft. sample for estimates
of cereal leaf beetle damage and leaf surface area measurements. These
leaves were placed on white paper, covered with clear plastic and
photocopied to provide a permanent record for later measurements. After
photocopying, these leaves were placed into the appropriate paper bags
containing the other leaves so as not to bias the dry weight estimates.

Surface areas of individual leaves were determined by measuring
the area of a number of wheat and oat leaves over a range of leaf

lengths using a polar planimeter.

Cereal Leaf Beetle Feeding Damage--The permanent records of the
subsampled leaves were processed by counting the number of feeding
scars in each leaf. Five clearly delineated feeding scars from each
leaf type for each crop and sampling date were measured with a micro-
scope using an ocular micrometer to estimate an average feeding scar
size. This information provided an estimate of feeding damage and a

method of estimating foliage surface area removed.

Cereal Leaf Beetle Population Samplingr-Population density esti—

 

mates of the egg, larval and pupal stages were estimated in the same
fields where the plants were sampled using the technique described by

Helgesen and Haynes (in press).

22

Two linear ft. of foliage were clipped at the soil surface at
30 sites within each sample area for each host crop at each sampling
date. The foliage was placed in labeled plastic bags, returned to the
laboratory and placed in storage at 44°F until processing. Eggs and
larvae (according to instar) were counted from each sample. The
foliage from these samples was dried in a forced air drier at 105°C
for more than 24 hours and then weighed. To accommodate the within—
generation p0pulation model (Helgesen and Haynes in press) egg input
was measured by counting and then destroying cereal leaf beetle eggs
laid in each of 10 two linear ft. sample areas at about three day inter—

vals. Egg input was measured at Gull Lake R and T and East Lansing - C.

Degree-Dayse-Both cereal crops and the cereal leaf beetle are

 

strongly dependent on temperature. It was necessary to use a measure
which combines both these parameters. Although there are some arguments
against using degree-days for this (Wang 1960), the use of degree-days
is a very practical method and is becoming generally accepted
(Baskerville and Emin 1969; Van Den Brink gt_gl. 1971). The method

used to calculate the accumulation of heat units was that of Baskerville
and Emin (1969).

Developmental temperature thresholds used for plant growth of
grasses (Alcock £3 31. 1968) was 42°F and for the cereal leaf beetle
larval instars the threshold and heat accumulation as determined by
Ruesink (personal communication) from experiments conducted by Helgesen
(1969) and Yun (1968) are given in Table III. Accumulation of heat
units from January 1 to August 31 in 1970 for Gull Lake and East Lansing

for bases 42°F and 48°F are provided (Appendices I and II). In addition

 

 

 

 

”J‘— -
“I.“ _
fl
.

Appendi
and the

lected

TABLE I

23
Appendices III and IV give the date, degree-days at bases 42°F and 48°F
and the number of days accumulated from April 20 when samples were col-
lected at Gull Lake and East Lansing in 1970.

TABLE III.--Accumulated heat units (base 48°F) for completion of
development of the cereal leaf beetle eggs larvae and

 

 

pupa
Degree days
Life stage (base 48°F)
Eggs 160
Larvae 220 (@ 55 for each instar)
Pupae 450

Total 830

 

 

 

 

lllll1‘l‘ ill i.‘ ..llllll'. .‘u‘l

RESULTS

The cereal leaf beetle and its host plant species are ecologically
inseparable. Spring adults must search for adequate hosts on which to
feed and oviposit their eggs and this selection must ensure larval sur-
vival. This study will attempt to quantify the growth of the plant
species which are most important from the human economic viewpoint as
well as for the economy of cereal leaf beetle survival.

The basic growth characteristics of the host plants were examined

to determine how the cereal leaf beetle interacts with its hosts.

Vegetative Phase—~In the area examined most thoroughly (Gull

 

Lake - R) the vegetative phase of wheat and oats differed significantly
in many respects. Wheat grew more rapidly and produced substantially
more foliage per sq. ft. of land area. Figure 2 shows the oven dry
weight of total foliage produced (g. per sq. ft.) by wheat and oats and
illustrates the basic shape of the growth curves at this site. From
these samples cereal leaf beetle egg and larval populations were
measured.

Additional samples, in close proximity to the previously men-
tioned samples, were collected to determine biomass of components which
comprise the vegetative phase. The top 3 leaves at any one point in
time were considered to be the most important component of the vegeta—
tive portion of the plant in growth and consumption by the cereal leaf

24

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26

beetle. The leaves below these, in many cases tended to be desiccated,
especially in wheat. Figure 3 illustrates the oven dry weight of the
top 3 leaves in each crop while Table IV shows the total leaf weight
and the per cent of the total represented by the weight of the top 3
leaves and shows that the proportion was greater in wheat than cats.

The surface area of individual leaves was estimated by measuring
the surface area of several leaves of known length for both wheat and
oats. Leaf length was squared to produce a linear relationship with

surface area using

2

s A w 24.56 + 0.037 (1 i); r 95.2

and

S A 0 2

88.8

ll

52.15 + 0.034 (1 i); r
where S A W and S A 0 are the surface area (sq. mm.) and l g and 1 i

are the leaf lengths squared (mm.) for wheat and oats respectively
(Figures 4 and 5).

Determining the surface area of foliage of wheat and oats re-
quired measuring the length of each leaf type. Rather than measure all
individual leaves, the total length of all leaves was measured and the
total number of individual leaves counted. By dividing total length of
all leaves of each type by the respective number of leaves, the average
leaf length was determined and these estimates are shown in Table V.
Using this method adds a bias to estimates of individual leaves (Ruesink,
personal communication) and an alternate method of determining leaf
length was then adOpted by measuring actual lengths of leaves subsampled
from each leaf type. These results are given in Table VI and these

estimates of leaf length were used to compute the surface area of

 

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TABLE IV.--0ven dry weight (g. per sq. ft.) of the top three leaves,
all leaves and the per cent of the total leaf weight con-
tributed by the top three leaves in winter wheat and spring
oats at each sample date and corresponding accumulated
degree-days (base 42°F)

 

 

 

 

 

Degree-days Oven dry wt. Oven dry wt. Top 3 leaves
Date (base 42°F) of top 3 leaves of all leaves as % of total
Wheat
4/23 121 0.69 .86 80.2
4/29 239 1.49 1.82 81.9
5/6 342 3.06 3.76 81.4
5/13 487 4.83 5.94 81.3
5/20 608 5.61 7.75 72.3
5/29 825 9.56 12.36 77.3
6/5 986 7.71 9.66 79.8
6/12 1,193 8.86 10.09 87.8
6/18 1,383 9.68 12.10 80.0
6/25 1,540 8.15 9.54 85.4
Oats
5/20 608 0.10 0.12 83.3
5/29 825 0.96 1.30 73.8
6/5 986 1.55 2.30 67.4
6/12 1,193 2.57 4.47 57.5
6/18 1,383 2.68 4.35 61.6
6/25 1,540 3.33 5.06 65.8
7/06 1,869 3.51 5.23 67.1
7/14 2,119 3.02 4.66 64.8

7/22 2,336 2.53 3.93 64.4

 

 

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31

TABLE V.--Leaf lengths (mm.) of the t0p three leaves of winter wheat
and spring oats calculated from total leaf length per leaf
type per sample divided by total number of leaves per leaf
type per sample at each sample date and corresponding
accumulated degree days (base 42°F) (n = 10; :_SE)

 

Degree-days

._._.__.- ..

 

Date (base 42°F) Leaf 1 Leaf 2 Leaf 3
Wheat
4/23 121 30.3 :_ 6.5 50.6 :_ 8. 41.9 i. 4.
4/29 239 52.8: 6.3 82.0: 9. 53.7: 6.
5/6 342 73.3 i_ 5.7 116.2 :_ 6. 76.9 i_ 5.
5/13 487 80.8 i. 6.9 128.7 :_l3. 108.8 :_10.
5/20 608 65.9 :_ 4.0 115.0 :. 7. 125.2 :. 5.
5/29 825 161.0 i_l4.8 183.9 :_15. 154.0 :_ 9.
6/5 986 168.0 :_10.1 204.2 :_47. 147.8 :,13-
6/12 1,193 170.2 :_13.2 174.3 : 17. 151.1 : 17.
6/18 1,383 184.6 :_22.1 191.5 : 19. 152.9 :_22.
6/25 1,540 160.0 :_28.4 173.2 : 14. 147.3 :_ 9.
Oats

5/20 608 51.5 :_15.3 97.7 :_ 9. 75.5 i 18.
5/29 825 67.1 :_ 3.9 132.1 :_ 8. 127.4 :_ 9.
6/5 986 88.3 :_10.8 174.4 :_l3. 146.3 : 8.
6/12 1,193 83.7 i. 9.9 169.6 :_ 8. 168.8_“ 8.
6/18 1,383 106.3 :_ 8.6 187.1 :_11. 191.2 i.13-
6/25 1,540 91.2 :_21.9 154.9 :_39. 155.2.“ 39.
7/06 1,869 101.1 :_10.3 171.5 i.14° 181.2 : 12.
7/14 2,119 108.2 :' 5.7 165.0 : 17. 169.5 :_15.
7/11 2,336 109.0 : 12.2 161.8 :_l7. 153.7 : 14.

 

 

 

32

TABLE VI.--Leaf length (mm.) of the tOp three leaves of winter wheat
and spring oats determined from subsampling five leaves of
each type at each sample date and corresponding accumulated
degree days (base 42°F) (n = 5; :_S.E.)

 

Degree-days

 

 

 

Date (base 42°F) Leaf 1 Leaf 2 Leaf 3
Wheat
4/23 121 30.2 :_ 8.5 57.8 :_ 3.8 52.2 :_ 6
4/29 239 55°“.i. 7.7 83.2 i; 6 0 55.8 i, 5
5/6 342 92.0 i 17.2 82.4 i 19.0 94.2 i 6
5/13 487 118.0 :_19.0 141.2 i_22.6 138.3 : 13-
5/20 608 90.4 :_23.9 130.4 i.14'3 126.4 1 6
5/29 825 182.0 i 32.4 168.4 : 27.4 181.0 :_ 7
6/5 986 196.8 :; 5.3 194.8 1 12.4 172.8 :_11.
6/12 1,193 205.2 :_12.8 191.4 :_ 8.6 167.4 : 12'
6/18 1,383 198.4 : 11.1 184.0 :_ 4.0 176.0 :_ 1
Oats
5/20 208 53.4 i: 13.9 110.0 _+_ 14.8 107.0 _+_ 4
5/29 825 115.8 i 6.6 156.8 1: 26.2 139.8 i 16.
6/5 986 139.0 : 17.0 182.4 : 16.9 193.4 :_ 6
6/12 1,193 117.8 1 11.4 213.2 :_ 5.7 239.0 :_10.
6/18 1,383 156.8 2“. 15.9 205.0 i 14.0 198.4 : 16.
6/25 1,540 148.8 f: 8.9 220.8 : 4.8 210.6 : 12.
7/6 1,869 154.8 1 10.4 220.0 i' 8.6 218.2 :_14.

 

33
foliage. Flag leaves from each crop were collected to confirm the

second method, their average lengths are given in Table VII.

TABLE VII.—-Flag leaf lengths (mm.) collected from fields of winter
wheat and spring oats at Gull Lake and East Lansing

 

 

(i S.E.)

Gull Lake Gull Lake East Lansing

(R-area) (T-area) (C-area)

June 17 June 17 June 25
Wheat 199.1 :_2.8 199.6 :_2.9 163.2 : 3.2

(n = 110) (n = 100) (n = 90)
Oats 165.4 f 2.9 152.3 :_2.5 166-3.i.4-0

(n = 99) (n = 100) (n = 100)

 

The number of new leaves produced per unit land area varies with
time, environmental conditions, and the tillering capacity of the
variety. Table VIII gives the percentage of each leaf type of the
total types for each sample.

As the plant matures, new leaves are produced at a decreasing
rate until all leaves are formed. The discrepancy noted in oats
(Table VIII) indicates that there were more than 6 leaves produced on
a stem and these were placed in the sixth leaf type category.

The difference in the amount of foliage per sq. ft. in wheat
and oats is not reflected in the number of leaves per stem but in the
number of tillers per sq. ft. Wheat produced more stems per unit land
area than oats using these varieties and under the environmental con-

ditions in 1970 (Table IX).

34

TABLE VIII.--Per cent composition of each of the top six leaves of the
total number of the top six leaves in each sample of
winter wheat and spring oats at each sampling date and
corresponding accumulated degree days (base 42°F)

 

 

 

 

 

 

Degree-days Z composition
Date (base 42°F) L l L 2 L 3* 5L 4 L 5 ‘L 6’
Wheat
4/23 121 3.4 27.5 17.5 12.0 8.0 1.5
4/29 239 29.5 26.5 18.5 11.5 8.0 6.0
5/6 342 26.0 23.5 19.5 14.5 9.5 7.0
5/13 487 24.5 22.5 18.5 14.0 10.0 10.0
5/20 608 24.5 21.0 17.5 15.5 ' 12.0 10.0
5/29 825 18.5 18.5 18.0 15.5 14.0 16.0
6/5 986 19.5 20.0 18.0 16.0 15.0 14.0
6/12 1,193 20.0 20.0 19.0 16.5 13.0 10.5
6/18 1,383 18.0 17.0 17.0 15.5 15.0 17.0
Oats
5/20 608 36.5 29.5 24.5 10.0 0.0 0.0
5/29 825 26.0 23.5 19.0 13.5 11.0 7.0
6/5 986 20.0 19.0 19.0 16.5 13.5 12.0
6/12 1,193 19.0 18.5 16.5 14.0 11.5 20.5
6/18 1,383 17.0 17.0 16.0 13.5 12.0 25.5

6/25 1,540 19.0 18.5 17.0 17.0 12.5 18.0

 

35

TABLE IX.--Number of plants, stems and stems per plant (per sq. ft.)
in winter wheat and spring oats at each sampling date and
corresponding accumulated degree days (base 42°F) (n = 10)

 

Degree-days

 

 

 

 

Date (base 42°F) No. plants No. stems Stems/plant
Wheat
4/23 121 26.4 82.4 3.12
4/29 239 28.6 115.5 3.89
5/6 342 27.3 118.8 3.98
5/13 487 32.6 128.5 3.94
5/20 608 26.3 117.2 4.47
5/29 825 29.7 98.3 3.31
6/5 986 25.0 73.3 2.93
6/12 1,193 20.2 81.4 4.03
6/18 1,383 26.6 97.4 3.36
6/25 1,540 28.8 97.2 3.37
7/6 1,869 23.7 67.9 2.86
Oats
5/20 608 9.8 14.6 1.49
5/29 825 18.5 41.7 2.25
6/5 986 12.3 29.8 2.34
6/12 1,193 14.1 33.0 2.34
6/18 1,383 19.9 31.4 1.58
6/25 1,540 15.9 38.2 2.40
7/6 1,869 12.7 32.6 2.57
7/14 2,119 14.7 41.3 2.80
7/22 2,336 17.0 34.1 2.01

 

36

Leaf surface area (excluding leaf sheaths) was calculated from
average leaf lengths (Table VI) using the equations from Figures 4 and 5
for individual leaves. This value multiplied by the number of stems
per sq. ft. gives surface area per sq. ft. for an individual leaf type.
For example, if the average length of a wheat leaf is 100 mm. and
there are 100 stems per sq. ft. the predicted surface area would be:

s A w = (24.56 + 0.037 (1002)) x 100
or 39456 sq. mm. per sq. ft. Table X gives the predicted number of
sq. mm. per sq. ft. of surface area of foliage for each of the top 3

leaves for wheat and oats.

Crop Height-—The height attained by a cr0p is easily measured.

 

Figure 6 shows the progression of height growth in wheat and oats and
illustrates the growth difference under the environmental conditions
at the Kellogg Farm. The shape of the acceleration phase of height
growth of these cr0ps differs and the maximum height of winter wheat

was about 100 cm. whereas oats grew to a maximum height of only 75 cm.

Head Components--The total oven dry head weight per sq. ft.

 

(including chaff, kernals and stems) was determined for each crop
(Figure 7). Again the difference in head weight between the two crops
is apparent although the morphological difference in head structure be-
tween wheat and oats must be considered. The number of heads per sq.

ft. were also counted (Figure 8).

Root Biomass--Variations in soil compactness made estimates of

 

root biomass difficult so they were not used in calculations. The
benefit of removing roots was the separation of stems belonging to

single root systems.

37

TABLE X.--Calculated surface area (sq. mm. per sq. ft.) of the top

three leaves of winter wheat and spring oats at each sampling

date and corresponding accumulated degree days (base 42°F)

(see text)

 

Degree days

Surface area (sq. mm. per sq. ft.)

 

 

 

 

 

Date (base 42°F) Leaf type 1 Leaf type 2 Leaf type 3
Wheat
4/23 121 4,804 12,209 10,331
4/29 239 15,400 31,296 15,584
5/6 342 40,122 32,763 41,923
5/13 487 69,358 97,949 94,095
5/20 608 38,316 76,615 72,161
5/29 825 122,889 105,557 121,569
6/5 986 106,841 104,716 82,783
6/12 1,193 128,817 112,333 86,389
6/18 1,383 124,402 107,288 98,336
Oats
5/20 608 2,162 6,753 6,430
5/29 825 21,145 36,991 29,843
6/5 986 21,100 35,902 39,422
6/12 1,193 17,258 52,688 65,778
6/18 1,383 27,854 46,472 43,630
6/25 1,540 30,711 65,274 59,559
7/6 1,869 26,209 55,705 50,828

 

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41

To develop a working relationship between wet sample foliage
and oven-dry weight of foliage per sq. ft., samples were collected over
a range of plant densities from Gull Lake and East Lansing on June 19
(Figure 9). Similar relationships were developed for each of the plant
components collected from Gull Lake - R at about weekly intervals and
are given in Table XI.

The per cent moisture in each of the components when sampled
was calculated (dry wt./wet wt. x 100) and is presented in Table XII.

Plant growth is variable from one site to the next even within
a single field. Plant samples were collected from fields of wheat and
oats where the land was rolling (Gull Lake - T). Two sets of samples
were taken; one on the top of a hill (Gull Lake — H T) and the other
at a lower area of the same field (Gull Lake - V T). Table XIII illus-
trates the differences in plant height, wet weight of foliage, oven
dry weight of heads and number of heads in wheat within the same field
at the two locations. Similar comparisons are made for oats (Table XIV).
The striking difference between the 2 areas within fields indicates the
superiority of the low area (Gull Lake V T) compared to the hill-tOp
samples (Gull Lake H T) in that growth was better in all the plant
components shown. These differences are assumed to be related to the
capacity of the lower area to hold moisture longer than the higher area.

The foliage weights (g. per sq. ft.) for the 2 areas at Gull
Lake (R and T) and the area at East Lansing from which cereal leaf
beetle eggs and larval were sampled are given in Appendices V, VI and

VII for wheat and oats.

-42-

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TABLE XI.--Regression equations to predict oven dry weight (g. per

43

linear ft.) from wet sample weight (g. per linear ft.) for
roots, stems, the top four leaves and heads of winter wheat

and spring oats throughout the growing season

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Roots
Wheat o.d. wt. = - .285 .478 w.s. wt. (gms.) n = 110, r = .79
Oats o.d. wt. = - .049 .281 w.s. wt. n = 90, r = .81
Stems
Wheat o.d. wt. = .503 .259 w.s. wt. n = 110, r = .72
Oats o.d. wt. = - .778 .227 w.s. wt. n = 90, r2 = .86
TOp leaf
Wheat o.d. wt. = .317 .231 w.s. wt. n = 100, r = .52
Oats o.d. wt. = .030 .197 w.s. wt. n = 90, r2 = .48
Second leaf
Wheat o.d. wt. = .642 .121 w.s. wt. n = 100, r = .38
Oats o.d. wt. = .137 .158 w.s. wt. n = 90, r = .58
Third leaf
Wheat o.d. wt. = .418 .136 w.s. wt. n = 100, r = .36
Oats o.d. wt. = .102 .157 w.s. wt. n = 90, r2 = .60
Fourth leaf
Wheat o.d. wt. = .233 .164 w.s. wt. n = 100, r = .36
Oats o.d. wt. = .065 .157 w.s. wt. n = 90, r = .61
Heads
Wheat o.d. wt. = -2.38 + 0.525 w.s. wt. n = 60, r = .86
Oats o.d. wt. = -l.59 + 0.531 w.s. wt. n = 48, r = .85

 

44

TABLE XII.--Per cent moisture remaining in plant components at each
sample date and corresponding accumulated degree-days
(base 42°F) (n - 10)

 

Degree-days Z moisture

 

Date (base 42°F) Roots Stems Leaf 1 Leaf 2 Leaf 3 Leaf 4

 

 

 

 

Wheat
4/23 121 73.1 86.9 86.6 85.5 83.4 82.9
4/29 239 68.6 88.3 87.6 87.4 87.3 86.3
5/6 342 59.8 86.6 86.0 86.0 86.2 85.2
5/13 487 56.2 85.7 83.8 83.1 83.5 85.7
5/20 608 63.0 85.3 79.6 73.5 73.8 73.0
5/29 825 66.4 81.9 77.8 80.4 75.9 67.6
6/5 986 57.3 78.7 75.6 73.8 62.3 44.1
6/12 1,193 48.2 70.7 66.6 71.7 65.6 61.4
6/18 1,383 38.8 61.7 39.8 19.4 17.5 17.0
6/25 1,540 53.3 63.8 53.8 53.6 57.3 64.3
7/6 1,869 48.7 58.3 28.8 25.2 25.7 30.0
Oats
5/20 608 70.4 91.5 96.9 85.5 94.1 100.0
5/29 825 83.5 92.3 91.2 89.7 89.9 91.0
6/5 986 82.2 91.7 89.0 87.7 87.3 87.3
6/12 1,193 67.9 87.0 85.0 81.8 82.9 82.6
6/18 1,383 68.8 84.2 82.3 82.1 82.9 84.1
6/25 1,540 71.7 81.2 79.3 79.2 80.8 81.9
7/6 1,869 68.0 75.6 62.8 66.4 70.1 69.3
7/14 2,119 72.1 75.2 64.9 72.2 74.1 72.2

7/22 2,336 73.3 72.1 62.0 62.3 63.9 67.4

 

45

TABLE XIII.--Within field comparison of plant height (cm.), total wet
sample weight of foliage (g.), oven dry weight of heads
(g.) and number of heads in springs oats (n = 3; : S.E.)

 

 

.._-—_ — -.....
_g a. - .- .. -...-- a a. -—

Degree days
Date (base 42°F) Gull Lake - HT Gull Lake - VT

 

Plant height

 

 

 

 

 

6/15 1,280 49.46 :_O.97 79.20 :_1.62

6/22 1,462 60.94 i 6.16 86.66 1:2.09

6/29 1,637 73.32 i 5.72 106.72 1 0.99

7/06 1,869 79.55 i 9.05 103.75 :_5.52

7/22 2,336 79.66 i 2.64 104.20 : 1.57
Wet weight total foliage

6/15 1,280 221.77 : 56.18 355.69 1 65.27

6/22 1,462 133.62 :_l3.54 418.81 : 84.59

6/29 1,637 126.61 : 14.24 313.83 :_61.74
Oven dry weight heads

7/22 2,336 19.44 i; 0.19 29.02 :_ 3.41

 

Number of heads

 

7/22 2,336 15.99 i; 1.51 26.28 + 4.58

 

46

TABLE XIV.—-Within field comparison of plant height (cm.), total wet
sample weight of foliage (g.) oven dry weight of heads (g.)
and number of heads in winter wheat (n = 3; :_S.E.)

 

Degree-days
Date (base 42° F) Gull Lake - HT Gull Lake - VT

 

Plant height

 

 

 

 

 

6/15 1,280 52.60 + 6.27 92.41 :_ 6.81
6/22 1,462 49.54 :_ 5.45 94.89 :_ 6.47
6/29 1,637 54.67 i. 9.41 88.78 :_ 9.0
Wet weight total foliage
6/15 1,280 73.15 :_12.97 181.07 i.45-32
6/22 1,462 56.12 i; 7.10 189.50 :_57.11
6/29 1,637 42.51 1:17.62 93.48 :_26.21
Oven dry weight heads
6/29 1,637 12.31 :_ 1.03 27.75 i. 7.71

 

Number of heads

 

6/29 1,637 17.71 i. 1.15 39.99 :_ 7.56

 

47

Further studies of cereal leaf beetle-host interactions need
not include measurements of all components of plant growth. Because
adult cereal leaf beetles oviposit and feed on the leaf tissue of their
hosts and the larvae also feed only on the leaves, this plant component
is most important. It is difficult and time consuming to separate each
leaf by its respective position on the stem of the plant, determine its
length and surface area. A more realistic approach is to develop rela—
tionships between plant components which are readily measurable. There-
fore a method which predicts surface area of foliage available to the
cereal leaf beetle would be most useful. An indirect method of pre-
dicting surface area can be determined using the dry weight of the
foliage. This functional relationship is given in Figure 10 and is
linear:

SA = 29513 + 34268 (DWL)
where SA is surface area (sq. mm. per sq. ft.) and DWL is oven dry

weight of leaves (g. per sq. ft.).

Cereal Leaf Beetle Population Densities--To assess feeding
damage to wheat and oats by the cereal leaf beetle, population esti-
mates of eggs and each of the 4 larval instars in both crops were made
within the same fields from which the plant components were measured
and also from Gull Lake — T and East Lansing - C. Sampling methods for
cereal leaf beetle population estimates were the same as those used by
Helgesen and Haynes (in press) described under methods. Results from
these samples are given in Appendices VIII, IX and X. Separate esti-

mates of egg input were also made (Appendix XI).

-43-

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49

Total feeding on each host crOp by the larval p0pulation is re-
lated to the total number of larvae produced per unit area of land.
This was determined by calculating the area under the total larval
population curve from the population estimates given in Appendix IX.
The total number of larvae produced per sq. ft. was 88.01 and 142.78
in wheat and oats reapectively. Feeding, however, is not pr0portional
to the total larvae produced because different amounts of food are

required by each of the four cereal leaf beetle instars.

Foliage Consumption Estimated from Cereal Leaf Beetle Population

 

Densities--A technique hereafter called 'first instar feeding equiva—
lents' was developed to account for the difference in consumption by
each instar. The results obtained by Wilson et a1. (1969) (Table XV)
were used to calculate this conversion.

TABLE XV.--Amount of foliage consumed by each instar of the cereal leaf

beetle and the corresponding first instar feeding equivalent
conversion (see text)

 

 

Area of folia e consumed First instar equivalent
Instar m m * conversion factor
1 18.6 1.00
2 53.4 2.87
3 111.0 5.97
4 459.5 24.23

 

*Mean of 21 and 26°C after Wilson g£_al. 1969.

50

The conversion factor is the expression of each of the instars
with respect to first instar feeding: for example the conversion factor
for the second instar is 53.4/18.6 - 2.87. These conversions effec-
tively weight the population by their respective amount of feeding.

Each population estimate (Table XVI) was multiplied by the appro-
priate conversion factor and the curves in Figure 11 show the effect of
the conversion. To determine the total amount of foliage consumed by
the larval populations in the 2 crOps, the area under the first instar
equivalent curves were calculated and divided by the develOpment time
(degree-days 48°F) to give the number of first instar equivalents pro—
duced in wheat (134976.6/55 = 2454.12) compared with 215962.5/55 =
3926.6 produced in oats. The respective amounts of foliage consumed in
each crop was estimated by multiplying the amount of foliage consumed
by a first instar larvae (18.6 mmz). Therefore, larvae consumed
45646.6 and 73034.6 mm2 of foliage in wheat and oats respectively.

The expression of foliage consumed through time by larvae is of
particular interest and cannot be ascertained by the preceding calcu-
lations. The amount of foliage consumed through time is cumulative
and therefore, the area under the first instar equivalent curve for

each cr0p was calculated at intervals of 100 degree days divided

48°F’
by the number of degree-days required for development (55 48°F) and
multiplied by the area consumed by a first instar larva (18.6 mmz).
Table XVI shows the calculated values of the cumulative numbers of first
instar equivalents and Figure 12 depicts the cumulative amount of

foliage consumed per sq. ft. by the cereal leaf beetle larval population

on wheat and oats.

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52

TABLE XVI.--Cumulative first instar feeding equivalents and cumulative
estimate of foliage consumed (sq. mm. per sq. ft.) deter-
mined from first instar equivalent incidence curves for
winter wheat and spring oats

 

Degree day interval Cumulative first Cumulative foliage

 

 

 

 

(base 48°F) instar feeding equivalents consumed
Wheat
300 - 400 7.79 144.89
401 — 500 70.12 1,304.23
501 — 600 389.54 7,245.44
601 - 700 1,075.15 19,997.79
701 — 800 1,779.70 33,474.42
801 - 900 2,290.52 42,603.67
901 - 1,000 2,446.33 45,501.74
1,001 — 1,100 2,454.12 45,646.63
Oats

400 - 500 7.79 144.89
501 - 600 54.54 1,014.44
601 - 700 428.50 7,970.10
701 - 800 1,324.45 24,643.77
801 - 900 2,399.60 44,623.56
901 - 1,000 3,217.63 59,847.92
1,001 - 1,100 3,724.05 69,267.33
1,101 - 1,200 3,903.22 72,599.89
1,201 - 1,300 3,926.59 73,034.57
1,301 - 1,400 3,926.59 73,034.57

 

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54

Foliage Consumed by Estimates of Leaf Damage-~An alternate esti—
mate of damage, independent of the number of larvae found on the
plants, was made by counting the number of feeding scars, through time,
on the top 3 leaves of the 2 host craps investigated. To predict the
amount of feeding on the leaves of a plant, and to compare these results
with the foliage consumed by a known larval population, the area of
foliage consumed was measured. The number of feeding scars per leaf on
each of the top 3 leaves of wheat and oats and the average scar area
(sq. mm.) is given in Table XVII. The amount of surface area removed
per leaf (SAR) was estimated by multiplying the number of scars by the
mean scar area at each time interval. Then using the estimate of the
number of leaves per sq. ft., the area of foliage removed was calculated
using the following formula: SAR = s. as . t where s is the number of
feeding scars per leaf type, as is the area of the feeding scars (in
sq. mm.) and t is the number of tillers (stems) per sq. ft. of land
area. SAR is the surface area removed (sq. mm.) per sq. ft. of land
area.

Table XVIII gives the values calculated from this equation for
the first 3 leaf types. The total sq. mm. of foliage removed from
these leaves for wheat and oats is shown in Figure 13. Table XIX com-
pares these 2 methods (Figures 12 and 13) of predicting feeding damage
and shows they are similar.

The first instar feeding equivalent method estimates damage to
the total plant while the methods of counting holes involved only the
top 3 leaves and may underestimate damage because damage occurs on

leaves below the third leaf down, especially on oats. No attempt was

55

TABLE XVII.--Number of feeding scars per leaf on each of the top three
leaves of wheat and oats and the average scar area (sq. mm.)

 

Number of feeding scars

 

Degree-days Scar area

 

 

 

 

Date (base 48°F) Leaf type 1 Leaf type 2 Leaf type 3 (sq. mm.)
Wheat
4/23 59 0 0 0 0
4/29 144 0 0.04 0.04 1.0
5/6 215 0.24 1.08 0.76 2.6
5/13 320 1.36 2.84 2.64 3.8
5/20 402 1.04 3.92 4.36 4.4
5/29 565 7.48 10.88 10.12 5.2
6/5 684 18.68 18.52 19.70 5.6
6/12 849 32.30 18.52 19.70 6.0
6/18 1,003 60.00 18.52 19.70 6.0
Oats
5/20 402 0.42 3.80 3.70 1.0
5/29 565 3.08 14.80 16.80 2.6
6/5 684 3.45 17.30 12.30 3.8
6/12 849 5.04 23.30 38.70 4.4
6/18 1,003 18.32 34.40 41.20 5.2
6/25 1,119 25.32 39.30 64.00 5.6
7/6 1,382 49.00 182.30 130.10 6.0

 

56

TABLE XVIII.--Cumulative feeding (sq. mm. per sq. ft.) on the top three
leaves of wheat and oats by a p0pu1ation of cereal leaf
beetles

 

Surface area consumed (sq. mm. per sq. ft.)

 

Degree-days

 

 

 

 

Date (base 48°F) Leaf type 1 Leaf type 2 Leaf type 3
Wheat
4/23 59 0 0 0
4/29 144 0 5 5
5/6 215 74 334 235
5/13 320 664 1,387 1,289
5/20 402 536 2,022 2,248
5/29 565 3,824 5,562 5,173
6/5 684 7,668 7,602 8,087
6/12 849 15,775 9,045 9,622
6/18 1,003 30,240 9,334 9,928
Oats
5/20 402 6 56 54
5/29 565 334 1,605 1,822
6/5 684 391 1,959 1,393
6/12 849 732 3,383 5,619
6/18 1,003 2,991 5,617 6,727
6/25 1,119 5,417 8,407 13,691
7/6 1,382 9,584 35,658 25,448

 

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58

TABLE XIX.--Final amount of square millimeters of foliage removed pre-
dicted by two different methods

 

 

 

Method Wheat Oats
lst instar equivalents 45,646.6 73,034.6
Damage to leaves 49,502.9 70,689.8
Difference - 3,856.3 + 2,344.8

 

made to separate damage caused by adult feeding. However, an estimate
of this is possible, especially early in the year on wheat when larvae
were not yet present in the crop (up to 300 degree-days).

The number of feeding scars in each of the top 3 leaves was dif-
ferent within each crop and between wheat and oats. Table XX shows the
per cent of the total number of scars contributed by each of the top 3
leaves. In wheat damage to the top leaf increased linearly with time a
corresponding decrease in damage to the second and third leaf. A
similar trend was not found in oats where damage to the second and
third leaf remained higher than on the first leaf. Table XXIshows the
per cent of the leaf surface available per sq. ft. consumed and a rela-
tionship similar to that given in Table IX is evident.

The importance of each of these leaves with respect to the
damage inflected on them is reflected in Table XXIby indicating that in
wheat the top leaf (flag leaf this late in the season) damage is about
2.6 fold greater than on the 2 leaves below it. This is not the case in
oats where damage on the lower leaves is greater than on the flag leaf.

Only by superimposing incidence the cereal leaf beetle first

instar feeding equivalents in wheat and oats over respective plant

59

TABLE XX.--Per cent utilization of the top three leaves of winter wheat
and spring oats by the cereal leaf beetle

 

 

 

 

 

Degree-days % utilization
Date (base 48°F) Leaf type 1 Leaf type 2 Leaf type 3
Wheat
4/29 144 0 50.0 50.0
5/16 215 11.5 51.9 36.5
5/13 320 19.9 41.5 38.6
5/20 420 11.2 42.1 46.8
5/27 565 26.3 38.2 35.5
6/5 684 32.8 32.5 34.6
6/12 849 45.8 26.3 27.9
6/18 1,003 61.1 18.8 20.0
Oats
5/20 402 5.0 47.9 46.7
5/29 565 8.9 43.2 49.0
6/5 684 10.4 52.3 37.2
6/12 849 7.5 34.8 57.7
6/18 1,003 19.5 36.7 43.9
6/25 1,119 19.7 30.6 49.7

7/6 1,382 13.6 50.4 36.0

 

60

TABLE XXI.--Per cent of the leaf surface available per sq. ft. consumed
by cereal leaf beetles on the top three leaves of wheat and

 

 

 

 

 

 

oats
Degree-days Z leaf surface consumed :7
Date (base 48°F) Leaf 1 Leaf 2 Leaf 3 X
Wheat
4/23 59 0.0 0.0 0.0 0.0
4/29 144 0.0 0.01 0.03 0.01
5/6 215 0.18 1.02 0.56 0.56
5/13 320 0.92 1.42 1.37 1.28
5/20 402 1.40 2.64 3.12 2.57
5/29 565 3.11 5.27 4.26 4.16
6/05 648 7.18 7.26 9.77 7.94
6/12 849 12.24 8.05 11.14 10.52
6/18 1,003 24.31 8.70 10.10 15.00
Oats

5/20 402 0.28 0.82 0.84 .75
5/29 565 1.58 4.34 6.10 4.27
6/05 684 1.85 5.46 3.53 3.88
6/12 849 4.24 6.42 8.54 7.17
6/18 1,003 10.74 12.09 15.42 13.00
6/25 1,111 17.64 12.88 22.99 17.69

7/06 1,382 36.57 64.01 50.07 53.25

 

61
growth curves can one appreciate the difference in impact of this insect
on the two crOp species. The cereal leaf beetle and plant growth
initiate development at different temperature thresholds (plant at
42°F and cereal leaf beetle larvae at 48°F). It was therefore imprac-
tical to plot the curves over 2 thresholds simultaneously. Instead
the x-axis is accumulated days from April 20 and does not detract
significantly from the curves plotted over degree-days.

However, Appendices III and IV provide the necessary relation—
ships between date, degree days (based 42°F and 48°F) and days from
April 20 at the corresponding sampling intervals at Gull Lake and
East Lansing.

In general it is apparent why oats is damaged more heavily than
wheat. Peak feeding by the cereal leaf beetle occurs in wheat when a
great deal of growth has already taken place. The wheat plant, by
overwintering and receiving fall and early spring moisture, has a well
established root system and therefore can probably withstand consider-
able defoliation. Under growth conditions in the study area, wheat
leaf biomass is greater than that for oats (Figure 14 B) and could be
responsible for diluting the larval population, especially during early
larval stages. In oats, the plants have barely emerged from the soil
with newly established root systems, often under moisture stress, when
the cereal leaf beetle adults begin to feed on the newly emerged oat
seedlings and oviposit eggs. Eggs hatched and larvae began feeding
before the plants were 20 cm. tall (Figure 14 A). Leaves grow rapidly
in oats and at peak larval feeding leaf length in both crops is com-

parable (Figure 14 C). The appearance of heads, on the other hand,

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66

occurred prior to or at about peak larval feeding in wheat but near the
end of larval feeding in oats (Figure 14 D).

In the 3 locations sampled (Gull Lake T and R and East Lansing -
C) cereal leaf beetle pOpulation densities as well as the amount of
foliage available for feeding were different. Figures 15 A - C illus-
trate these differences showing that cereal leaf beetle populations
were highest at Gull Lake - T, slightly lower at Gull Lake - R and
much lower at East Lansing - C. The total amount of foliage (oven
dry weight per sq. ft.) on which the cereal leaf beetle fed (Figures
15 A - C) was greatest at East Lansing - C less at Gull Lake - R and
lowest at Gull Lake T.

Table XXII shows the approximate amount of total foliage per
sq. ft. available in each area at peak larval feeding. The differences
between areas in the foliage available cannot be directly attributed
to cereal leaf beetle densities but do indicate that damage caused by
this feeding would be more intense when less foliage is available. A
portion of the difference in crop growth may be related to the differ-
ence in total rainfall received during May, June and July (Table XXIII)
and especially during June, Gull Lake received 2.35 inches less than
East Lansing. Heat units, accumulated from January 1 do not seem to be
appreciably different between the two areas (Table XXIV), although less
heat was accumulated at East Lansing.

From larval populations in these 3 areas the amount of foliage
consumed on each crop was calculated (Table XXV), also indicating the
population levels attained in each area. Egg input by the cereal leaf

beetle was also measured in each of these areas and was used to predict

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70
survival (1 - mortality) of larvae and the total cereal leaf beetle
generations (Table XXVI) using the model given by Helgesen and Haynes
(in press).

TABLE XXII.-—Tota1 biomass of foliage (g. per sq. ft.) at peak cereal
leaf beetle larval feeding

 

 

Area Wheat Oats
Gull Lake - R 35 16
Gull Lake - T 15 16
East Lansing - C 54 32

 

TABLE XXIII.--Tota1 monthly rainfall (in.) for May, June and July at
Gull Lake and East Lansing

..-- .—
—-—.-..-.—.- _.

Monthly Rain

11
t?

 

 

Area May June July
Gull Lake 4.09 3.62 4.85
East Lansing 2.40 5.97 6.98

 

TABLE XXIV.-—Accumulated heat units from January 1 at base 42°F and
48°F for Gull Lake and East Lansing

 

.. -_-.—-—--» m-.-.—_--.u-. - ...
- - - _—

-- o - —
-... - -. -..M‘ - ----—_ .. - - _—

Accumulated heat units from January 1

 

May June July
Area 42° 48° 42° 48° 42° 48°

 

Gull Lake 587 422 770 597 911 731

East Lansing 562 406 721 551 891 711

 

71

TABLE XXV.--Foliage consumed (sq. mm. per sq. ft.) calculated from
cereal leaf beetle population estimates converted to first
instar equivalents

 

 

Area Wheat Oats
Gull Lake - R 45,646.6 73,034.6
Gull Lake - T 61,259.8 90,356.1

East Lansing - C 7,883.1 28,982.2

 

72

TABLE XXVI.--Prediction of larval survival and mortality and generation
survival and mortality from the within generation cereal

leaf beetle model (Helgesen and Haynes in press)

 

 

 

 

 

 

 

Winter Spring
wheat oats
1970

Gull Lake - R
egg input (log) 2.40739 2.58535
larval survival 0.099 0.131
larval mortality 0.901 0.869
generation survival 0.069 0.091
generation mortality 0.931 0.909

Gull Lake - T
egg input (log) 2.3541 2.8488
larval survival 0.103 0.089
larval mortality 0.898 0.911
generation survival 0.072 0.063
generation mortality 0.928 0.938

East Lansing - C
egg input (log) 1.8319 2.1804
larval survival 0.138 0.209
larval mortality 0.862 0.791
generation survival 0.097 0.146
generation mortality 0.903 0.854

 

DISCUSSION

In cereal crops the production is the number of bushels of grain
per acre that can be harvested by man. However, for insects that feed
on portions of the plants, production is the useful food produced by
the plant. In the case of the cereal leaf beetle, the production of
leaves suitable for survival of the insects is most important because
this species does not usually feed on any other plant part. Oviposition
sites are specific to portions of the leaves (Table XXVII after Castro
lggflgl. 1965) and feeding occurs only on the upper leaf surface except
under unusual circumstances (Merrit and Apple 1966).

The importance of local (within-field) conditions is illustrated
by the differences in plant growth shown in Tables XIII and XIV from
results obtained at the Gull Lake - T site. Between-field variation in
growth indicates significant differences between Gull Lake - T and
Gull Lake - R (Figures 15 A and 15 B) and even greater variation between
the Gull Lake (T and R) sites and the East Lansing - C site (Figures
15 A and 15 C). Quantitative differences in growth of these areas is
better expressed in terms of growth rate (g. per degree—day per sq. ft.)
using:

wz’wl

dz'dl

where C (after Watson 1958) is defined as crop growth rate and W is the

C:

oven dry weight of foliage (g. per sq. ft.) and d is in degree-days

73

74

TABLE XXVII.--Observations on egg laying behavior of the cereal leaf
beetle on oat seedlings in the laboratory (after
Castro £5 31. 1965)

 

 

Number of Per cent

Place on leaves eggs eggs

Upper surface 209 98.5

Lower surface 3 1.5
In whorl 7 3.35
Basal 1/3 of leaf 125 59.75
Central 1/3 of leaf 77 36.90
Apical 1/3 of leaf 0 0.00
Occur singly 87 41.70
Occur in twos 88 42.17
Occur in threes 24 11.50
Occur in fours 8 3.83

Occur in five or more 5 2.88

‘II1

 

75
(base 42°F). Tables XXVIII and XXIX compare these 3 areas at their
respective sampling times for wheat and cats. The variation exhibited
between these areas makes it difficult to project the influence of the
cereal leaf beetle on crops in different areas without having some
measure of the amount of foliage available to that population in each
area. The differences in growth and in the total amount of foliage
produced per unit land area may bias an observer if attempts are made
to extrapolate from the amount of damage caused by the cereal leaf
beetle in a field to the cereal leaf beetle population. Under ideal
plant growth conditions the damage by cereal leaf beetle larvae will
be diluted as more foliage occurs through a high plant growth rate and
increased tillering. In this case, estimates of cereal leaf beetle
density would be underestimated and if environmental conditions the
following year were poor or if the cr0p was planted late, damage
caused by the cereal leaf beetle could be considerable. This problem
is an important consideration when rating damage caused by the cereal
leaf beetle because the ratings used in one particular year may not
pertain to the same ratings used the next year if plant growth and
production is altered by the environment.

Frequent sampling within a season appears unnecessary as damage
and plant growth may be estimated by a few samples of plants and larvae
collected at critical times (e.g. initial, peak and end) during a
season.

An accurate estimate of feeding by each instar of the cereal
leaf beetle is essential for proper calculation of first instar equi-

valent feeding and additional estimates to those of Wilson gt al. (1969)

76

TABLE XXVIII.--Crop growth rate of winter wheat (g. per degree-day
(base 42°F) per sq. ft.) at Gull Lake (R and T) and
East Lansing - C

 

X degree-days Crop_growth rate
between 2 samples ' Gull Lake (R) Gull Lake (T) East Lansing (C)

 

412.5 0.023
419.5 0.013

471.5 0.017

 

520.5 0.049 0.011
577.0 0.041
609 0.045 0.016
660.5 0.066
732 0.086 0.046
756 0.105
822 0.044 0.015
894 0.71
1,044.5 0.061 0.027
1,071 0.56
1,238 0.045 0.028
1,263 0.105
1,435.5 0.017
1,437 0.045
1,445 0.0

1,599 0.0 0.050

 

77

TABLE XXIX.-—Crop growth rate of spring oats (g. per degree—day) (base
42°F) per sq. ft. at Gull Lake (R and T) and East Lansing
- C

 

Crop growth rate

 

X'degree-days
between 2 samples Gull Lake (R) Gull Lake (T) East Lansing (C)

 

 

577 0.006
609 0.005 0.006
660.5 0.008
732 0.011 0.015 7
756 0.017
882 0.023 0.025
894 0.051
1,044.5 0.032 0.034
1,071 0.055
1,238 0.013 0.033
1,263 0.083
1,437.5 0.034 0.090
1,445.5 0.061
1,600 0.032 0.071

1,609 0.0

 

78
should be made under field conditions and on different crops to provide
a more concrete base for estimating damage.

Related to this is the problem of food quality and its impact
on host preference. The preference for one crop over another when the
plants are of similar age is complicated by plant variety, but when oat
seedlings become available in the field, high densities of adult cereal
leaf beetles appear in the fields of oat seedlings and begin feeding
and ovipositing. In general, there is an increase in beetle density
in spring planted oats. In some years however (ex. Gull Lake 1971)
cereal leaf beetle populations in wheat are very low and higher densities
of larvae appear in oats. This usually results when wheat is planted
early and the foliage is more mature than usual when the beetles move
out of their overwintering sites into the grains. A study designed to
investigate this was initiated in 1972 where winter wheat was planted
at several different dates throughout the fall.

To obtain an index of succulence, the ratio of oven dry weight
to wet sample weight (in per cent) was calculated (Table X11) and the
mean values for the top three leaves are shown in Figure 16. Some
variation in the per cent moisture of the wet sample weight resulted in
the length of time taken for the samples to be processed after they
were brought from the field. The shape of the curves and their position
with respect to the first instar equivalent feeding curves indicates
that this measure is a realistic approach to succulence of leaves but a
more exhaustive study of this mechanism is warranted. An additional
observation in this regard is the amount of surface area removed from
the top leaf of wheat (Table XVII). A much greater proportion was re-

moved from this top leaf (the flag leaf) than from lower leaves of

-79-

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1 3
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80

wheat. This did not seem to be the case with oats where the lower
leaves were fed on to a greater extent than the top leaf, likely because
the flag leaf was in the process of forming as the cereal leaf beetle
population was entering the prepupal stage.

The actual mechanism causing the movement of beetles to less
and less mature foliage has not been fully investigated and at present
succulence seems to be the best word to describe a phenomenon which may
be biochemical in nature.

The importance of leaf removal to grain yield was studied by
Womack and Thurman (1962) who removed different amounts of leaves from
winter wheat and winter oats. Their results (Table XXX) show that in
wheat, leaf removal 1 week before the boot stage caused significant
reduction in yield where as in winter oats, this effect is not evident.

It is not readily apparent that feeding damage caused by the
cereal leaf beetle is directly comparable to the actual removal of
whole leaves. In some cases larvae may intersect the energy transfer
from the leaf to the developing head by feeding. Often, this feeding
causes increased desiccation of the leaves contributing to rapid leaf
senescence which is important to final yield (Watson 1956) and un-
doubtedly interrupts photosynthetic activity of the leaf surface by
reducing the photosynthetic efficiency of the plant leaves. Because
other portions of the plant are capable of photosynthetic activity
(i.e. leaf sheaths, stems) more pressure is probably placed on these
components to provide the necessary assimilates that are eventually
translated into yield. However, Allison and Watson (1966) found that
the parts above the highest node in wheat and barley supply most of the

dry matter that fills the grain. Earlier, Watson (1956) stated that a

 

81

TABLE XXX.--Grain yields of Chancellor wheat and Arkwin oats for 5
levels of leaf area removal at 4 stages of plant develop-
ment (after Womock and Thurmon 1962)

 

Grain yield, bu. per acre

 

Z leaf removal

 

Stage of development 0 10 20 30 40 Average

 

Chancellor wheat

 

3 — year average, 1958 - 1961

 

 

One week before boot 26 25 23 23 23 23.7

Boot 27 25 24 22 23 24.2

One week after boot 29 28 26 25 24 26.3
Average 27.4 25.7 24.4 23.7 22.5

2 - year average 1958 - 1961

 

 

One week before boot 30 29 28 27 25 27.5
Boot 31 28 29 27 26 27.9
One week after boot 34 31 30 29 20 29.8
Two weeks after boot 31 32 28 28 28 29.3
Average 31.2 30.0 27.3 27.5 26.2
Arkwin oats

 

3 — year average 1958 - 1961

 

 

One week before boot 46 43 45 39 40 42.3
Boot 49 41 44 37 40 42.2
One week after boot 42 41 44 42 39 42.0
Average 46.3 42.1 43.6 39.9 39.6
2 - year average 1959 - 1961
One week before boot 63 59 59 52 53 57.1
Boot 64 56 58 46 50 54.8
One week after boot 58 56 53 56 51 54.7
Two weeks after boot 63 60 60 57 51 58.2

Average 61.8 57.9 57.4 52.9 51.1

 

82
high leaf area index at ear emergence and slow senescence of the leaves
was the most important determiner of yield. This was challenged by
Gregory (1966) who argued that yield depended on the number of ears
produced thereby emphasizing the importance of tillering which would
increase leaf area and the number of ears. There is, therefore, a
definite need to examine the physiological effect on plants fed on by
the cereal leaf beetles and although this must be conducted carefully
it should be a field study rather than an environmental chamber type
investigation.

One of the problems encountered during this investigation was the
quantative measure of surface area removed from leaves by the cereal
leaf beetle. Variability in leaf size, feeding scar size and the number
of feeding scars per leaf seems to indicate that some electronic method
of quantifying damage would be most valuable and would standardize the
present methods of visual estimates. Such techniques are being con-
templated and initial investigations are under way (Fisher, Electrical
Engineering, M.S.U.).

Because of the variation found in plant growth there is a def-
inite need for a specific model of growth throughout the range of the
cereal leaf beetle under variable environmental conditions. Yield was
not a primary concern of this study because of such variability and
reduction in yield could not be attributed to cereal leaf beetle
feeding. The effect that the cereal leaf beetle will have in the
prairie regions of North America is unknown. In northern areas, winter
grains will not survive and the damage caused to a spring grain monocul—

ture by the cereal leaf beetle can only be fearfully anticipated.

83

This study has attempted to bring together the plant and the
insect and to place an insect's plant hosts in the prOper perspective.
Data from this investigation are limited to 1 year and principally
1 area. Much of the information is descriptive and awaits a more exten-
sive analyses. Integrating plant growth with dynamic models of the
cereal leaf beetle over a much wider range of conditions is suggested.
The importance of the plant in the dynamics of a host specific insect I
must not be underestimated as it seems to have been in the past. Per- L
haps this is due to the entomologist's unwillingness to attempt to 1
quantitatively relate the two or the botanist's unwillingness to con-
sider the insect in relation to the plant he is studying. These remarks
are not intended for the few of each profession who have tried but
for those who have considered the interaction unimportant.

Until I attempted to bring the two together I felt that it was
a plant physiologist's job to define plant growth and the entomologist's
duty to define what the insect does to its host. Perhaps this is true
but because the two are intertwined, it seems impossible to separate

the insect from its host.

SUMMARY AND CONCLUSIONS

This investigation cannot be considered definitive on the rela-
tionship between the cereal leaf beetle and its primary hosts. The
principle value of this study is that it describes basic relationships
between an insect and its hosts and points out the complexities of the
interaction. The dynamics of the cereal grains within a season are
complex and working models of field plant growth and potential yield
are essential.

To measure the impact of the cereal leaf beetle on small grains
over a large geographical area, many of the factors measured in this
study need further investigation under a range of environmental condi-
tions to provide predictive models of damage. It is essential to be
able to determine the magnitude of the insect population and to obtain
an accurate fix on important crop growth parameters such as leaf surface
per unit area. This can be accomplished within the present framework
of the 'Cereal Leaf Beetle Population Dynamics Survey'.

This study has provided the apprOpriate techniques to convert
conventional population density estimates into a realistic feeding
entity called first instar feeding equivalents. From this information
an accurate estimate of the amount of foliage removed by the population
is available. Unfortunately, the transition from the amount of foliage
removed by the cereal leaf beetle to the reduction of yield is not
simple. By removing leaf tissue, this insect causes reduction in the

84

 

85
photosynthetic capacity of the crap. Further studies are suggested
which will allow the translation of this subtle reduction of the
plant's capacity to photosynthesize into a reduction of yield, which
lies within the realm of a field plant physiologist.

There are several points that summarize the concepts and findings
of this paper: (1) a technique has been developed from data in the
literature to translate cereal leaf beetle larval populations into
feeding equivalents which enable estimates of leaf surface area removed,
(2) a significant interaction between cereal leaf beetle density and
plant damage relates to the synchronization between the plant growth
rate and the feeding rate of the insect population, (3) the most signifi-
cant density dependent factor determined by Helgesen and Haynes (in
press) was competition for food and this study points out that this
competition occurs on the last or flag leaf of winter wheat and on
several or all leaves of spring oats, (4) the growth pattern of the
plant is a highly correlated system and this study offers a series
of regression equations for converting various plant growth measurements,
(5) only a few parameters are required to describe the principle total
plant growth products, and (6) the model will be incomplete without the
ability to translate leaf damage caused by cereal leaf beetle feeding

into grain yield.

 

LITERATURE CITED

LITERATURE CITED

Alcock, M. B., J. V. Lovett and D. Machin. 1968. Techniques used in
the study of the influence of environment on primary pasture
production in hill and lowland habitats. 13_The measurement
of environmental factors in terrestrial ecology. R. M. Wadsworth,
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Allison, J. C. S. and D. J. Watson. 1966. The production and dis—
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Baskerville, G. L. and P. Emin. 1969. Rapid estimation of heat
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Blackman, V. H. 1919. The compound interest law and plant growth.
Ann. Bot. 33:353.

Blackman, G. E. 1959. Responses to environmental factors by plants
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p. 525-556.

Borrill, M. 1959. Inflorescence initiation and leaf size in some
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Bunting, A. H. and D. S. H. Drennan. 1966. Some aspects of the
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J. D. Ivins, eds. Butterworths, London. p. 20-38.

Castro, T. R., R. F. Ruppel and M. S. Gomalinski. 1965. Natural
' history of the cereal leaf beetle in Michigan. Mich. State
Univ. Agr. Sta. Quart. Bull. 47:623-653.

Crossley, D. A. 1963. Consumption of vegetation by insects. .LE
Radioecology. V. Schultz and A. W. Klement, eds. p. 431—440.

-Evans, G. C. and A. P. Hughes. 1962. Plant growth and the aerial
environment. 111. On the computation of unit leaf rate.
New Phytol. 61:322-327.

Friend, D. J. C. 1965. Tillering and leaf production in wheat as
affected by temperature and light. Can. J. Bot. 43:1063-1075.

86

87

Friend, D. J. C. 1966. The effect of light and temperature on the
growth of cereals. ‘12 The growth of cereals and grasses.
F. L. Milthorpe and J. D. Ivins, eds. Butterworths, London.
p. 181-199.

Gallum, R. L., R. F. Ruppel and E. H. Everson. 1966. Resistance of
small grains to the cereal leaf beetle. J. Econ. Entomol.
59:827.

Gallum, R. L., R. T. Everly and W. T. Yamazaki. 1967. Yield and
milling quality of Monon wheat damaged by feeding of cereal
leaf beetle. J. Econ. Entomol. 60:356-359.

Gregory, F. G. 1956. General aspects of leaf growth. 12_The growth
of leaves. F. L. Milthrope, ed. Butterworths, London. p. 3-17.

Helgesen, R. G. 1969. The within—generation dynamics of the cereal
leaf beetle, Oulema melanopus (L.) Ph.D. Thesis, Michigan State
Univ. 96 p.

 

Helgesen, R. G. and D. L. Haynes. In press. Population dynamics of
the cereal leaf beetle, Oulema melanopus (L.): A model for age
specific mortality. Can. Entomol.

 

Hogg, W. H. 1965. Climatic factors and choice of site, with special
reference to Horticulture. In_Biological significance of
climatic changes in Britain. Symp. Inst. Biol. 14:141—155.

Jewiss, O. R. 1966. Morphology and physiology aspects of growth of
grasses during the vegetative phase. In The growth of cereals
and grasses. F. L. Milthorpe and J. D. Ivins, eds. Butterworths,
London. p. 39-54.

McCloud, D. E., R. J. Bula and R. H. Shaw. 1964. Field plant physiology.
Advan. Agron. 16:1-58.

Merrit, D. L. and J. W. Apple. 1969. Yield reduction of oats caused
by the cereal leaf beetle. J. Econ. Entomol. 62:296-299.

Miczulski, B. 1971. Studies regarding the bionomics, economic impor—
tance and natural control affecting Oulema species in Poland.
Agr. Univ. of Lublin, Project No. E21-ENT-l4. 51 p.

Pedigo, L. P., J. D. Stone and R. B. Clemen. 1970. Photometric device
for measuring foliage loss caused by insects. Ann. Entomol.
Soc. Amer. 63:815-818.

Ruesink, W. G. 1972. The integration of adult survival and dispersal
into a mathematical model for the abundance of the cereal leaf
beetle, Oulema melanopus (L.). Ph.D. Thesis, Michigan State
Univ. 80 p.

 

 

 

illllllllllllllll Illll‘ 1' II ll '3': I III! [I 1

88
Ryle, G. J. A. 1966. Physiological aspects of seed yield in grasses.
In The growth of cereals and grasses. F. L. Milthorpe and

J. D. Ivins, eds. Butterworths, London. p. 88—105.

Schillinger, J. A. 1969. Three laboratory techniques for screening

small grains for resistance to the cereal leaf beetle. J. Econ.

Entomol. 62:360-363.

Shade, R. E. and M. C. Wilson. 1967. Leaf vein spacing as a factor
affecting larval feeding behavior of the cereal leaf beetle,

Oulema melanopus (Coleoptera:Chrysomelidae). Ann. Entomol.
Soc. Amer. 60:493-496.

 

Thorne, G. N. 1966. Physiological aspects of grain yield in cereals.
In The growth of cereals and grasses. F. L. Milthorpe and
J. D. Ivins, eds. Butterworths, London. p. 88-105.

 

U.S.D.A.--APHS--PPD. 1971. Cereal leaf beetle quaranteen map. 1 p.

Van Der Brink, C., N. D. Stroman and A. L. Kenworthy. 1971. Growing
degree-days in Michigan. Res. Rpt. 131:1-49. Michigan State
Agr. Expt. Stn., East Lansing, Michigan.

Wang, J. Y. 1960. A critique of the heat unit approach to plant
response studies. Ecology 41:785-790.

Watson, D. J. 1947. Comparative physiological studies on the growth
of field craps. 1. Variations in net assimilation rate and
leaf area between species and varieties, and within and between
years. Ann. Bot. (N.S.) 11:41-89.

Watson, D. J. 1956. Leaf growth in relation to crop yield. IE_The
growth of leaves. F. L. Milthorpe, ed. Butterworths, London.
p. 178-191.

Watson, D. J. 1958. The dependence of net assimilation rate on leaf
area. Ann. Bot. (N.S.) 22:37-54.

Webster, J. A. and D. H. Smith, Jr. 1971. Seedlings used to evaluate
resistance to the cereal leaf beetle. J. Econ. Entomol.
64:925-928.

Wellso, S. G., J. A. Webster and R. F. Ruppel. 1970. A selected
bibliography of the cereal leaf beetle, Oulema melanoPus
(Coleoptera:Chrysomelidae). Bull. Entomol. Soc. Amer.
16:85-88.

 

Whitehead, F. H. and P. J. Meyerscough. 1962. Growth analysis of
plants. The ratio of mean relative growth rate to the mean
relative rate of leaf area increase. New Phytol. 61:314-321.

3‘

89

Williams, W. A., R. S. Loomis and C. R. Lepley. 1965. Vegetative
growth of corn as affected by population density. 11. Com-

ponents of growth, net assimilation rate and leaf area index.
Crop Science 5:215-219.

Wilson, M. C. and R. E. Shade. 1964. The influence of various Graminae
on weight gains of post diapause adults of the cereal leaf

beetle, Oulema melanopa (ColeOptera:Chrysomelidae) Ann. Entomol.
Soc. Amer. 57:659-661.

Wilson, M. C., R. E. Treece, R. E. Shade, K. M. Day and R. K. Stivers.

1969. Impact of cereal leaf beetle larvae on yield of oats.
J. Econ. Entomol. 62:699-702.

Womack, D. and R. L. Thurman. 1962. Effect of leaf removal on grain
yield. Crop Science 2:423-426.

Yun, Y. M. 1967. Effect of some physical and biological factors
on the reproduction, development, survival and behavior of
the cereal leaf beetle, Oulema melanopus (L.) under laboratory
conditions. Ph.D. Thesis, Michigan State Univ. 153 p.

II"! '1' I‘ll 1 I III! [III [lull III
II Illa!!! [II I. I [I

 

 

APPENDICES

 

I‘lllnll'llll‘l‘lll l
illllll‘ujll

Appendix Ia.

Accumulation of heat units (degree—days) from January 1 to

August 31, 1970 at East Lansing, Michigan.

 

 

Threshold 42°F

 

 

Day Jan Feb Mar Apr May Jun Jul ' Aug
1 0 3 7 22 331 923 1685 2612
2 0 3 7 22 343 947 1723 2639
3 0 3 7 22 352 961 1759 2671
4 0 3 9 22 363 975 1785 2691,
5 0 3 9 23 372 993 1807 2714
6 0 3 9 25 375 1017 1832 2743
7 0 3 10 27 385 1041 1861 2772
8 0 3 10 40 411 1069 1891 2802
9 o 3 10 49 440 1101 1915 2831

10 0 3 10 51 470 1134 1937 2861
11 0 3 10 51 494 . 1168 1968 2891
12 0 3 10 55 510 1200 2001 2923
13 0 3 10 59 524 1222 2035 2953
'14 0 3 10 .66 532 1247 2073 2985
15 0 3 10 75 554 1274 2107 3019
16 0 3 10 85 572 1306 2135 3051
17 0 3 10 96 580 1344 2165 3078
18 0 5 10 102 594 1375 2196 3104
19 0 5 12 102 622 1395 2220 3134
20 0 5 14 108 645 1409 2234 3164
21 0 5 17 114 671 1425 2254 3186
22 0 6 19 122 699 1445' 2276 3214
23 0 6 20 135 722 1471 2300 3240
24 0 7 20 151 745 1501 2330 3264
25 0 7 21 1171 768 1517 2364 3292
26 0 7 22 191 787 1535 2398 3324
27 0 7 22 , 215 799 1553 2435 3354
28 1 7 22 239 313 1574 2471 3388
29 2 7 22 269 835 ‘1606 2506 3414
30 2 7 22 299' 863 1644 2540 3445
31 2 7 22 299 893 1644 2576 3470

Appendix Ib. Accumulation of heat units (degree-days) from January
1 to August 31, 1970 at East Lansing, Michigan

 

Threshold 48°F

 

 

VDay Jan Feb Mar Apr May Jun Jul Aug
1 0 0 0 0 206 636 1222 1963
2 0 0 0 0 214 654 1254 1984
3 0 0 0 0 220 662 1284 2010
4 0 0 0 0 227 671 1304 2024
5 0 0 0 0 232 683 1320 2041
6 0 0 0 0 233 701 1339 2064
7 0 0 0 0 239 719 1362 2087
8 0 0 0 8 259 741 1386 2111
9 0 0 0 15 282 767 1404 2134

10 0 0 0 15 306 . 794 1420 .2158
11 0 0 0 15 324 822 1445 2182
12 0 0 0 17 335 848 1472 2208
13 0 0 0 -18 344 864 1500 2232
14 0 0 0 21 347 883 1532 2258
15 0 0 0 27 363 904 1560 2286
16 0 0 0 33 375 930 1582 2312
17 0 0 o 39 379 962 1606 2333
18 0 0 0 41 389 987 1631 2353
19 0 o 0 41 411 1001 1649 2377
20 0 0 0 43 428 1010, 1657 2401
21 0 0 0 45 448 1021 1671 2417
22 0 0 0 50 470 1035 1687 2439
23 0 0 0 58 487 1056 1705 2459
2“ 0 0 0 '68 504 1080 1729 2477
25 0 0 0 82 521 1090 1757 2499
26 0 0 0 96 534 1102 1785 2525
27 0 0 0 114 540 1114 1816 2549
28 0 0 0 132, 550 1129 1846 2577
29 0 0 0 156 566 1155 1875 2597
30 0 0 0 180 588 1187 1903 2622
31 0 0 o 180 612 1187 1933 2641

Appendix IIa. Accumulation of heat units (degree—days) from January 1
to August 31, 1970 at Gull Lake Biological Station,

 

 

 

Michigan.
Threshold 42°F

Day Jan Feb Mar Apr May Jun Jul Aug
1 0 1 3 '17 294 909 1718 2665
2 0 1 3 17 302 932 1756 2695
3 0 l 3 17 311 948 1794 2725
4 0 l 5 17 327 964 1820 2744
5 0 l 5 17 338 986 1845 2766
6 0 1 6 18 342 1006 1869 2792
7 0 1 6 19 352 1032 1901 2820
8 0 1 6 29 376 1062 1929 2852
9 0 1 6 40 402 1093 1954 2884
10 O 1 6 42 427 1125 ' 1980 2914
11 0 1 6 42 450 1159 2012 2945
12 0 1 6 .46 470 1193 2046 2977
13 0 1 6 51 487 1221 2081 3009
14 0 1 6 59 495 1250 2119 3043
15 0 1 6 68 516 1280 2155 3071
16 0 1 6 78 530 1312 2184 3105
17 0 1 6 87 540 1351 2214 3132
18 0 2 6 90 554 1383 2246 3158
19 0 2 8 y 90 582 1406 2272 3192
20 0 2 9 96 608 1421' 2292 3224
21 0 2 13 100 634 1440 2313 3246
22 0 2 16 109 - 664 1462 2336 3271
23 0 2 17 '121 692 1490 2356 3295
24 0 3 17 132 720 1520 2385 3319
25 0 3 17 147 746 1540 2420 3350
26 0 3 17 165 764 1562 2456 3383
27 0 3 17 187 776 1580 2490 3415
28 0 3 17 209' . 800 1603 2528 3451
29 0 3 17 239 825 1637 2560 3479
30 0 3 17 268 853 1679 2596 3510
31 0 3 17 268 881 1679 2629 3534

 

 

11 lllil‘f'lllli'll I'll-'1 ‘I.|’III|‘
I‘ll-lull!

Accumulation of heat units (degree-days) from January 1
to August 31, 1970 at Gull Lake Biological Station, Michigan

Appendix IIb.

 

 

 

_J: :=====
Threshold 48°F
Day Jan Feb Mar Apr May Jun Jul Aug
1 0 0 0 3 187 ‘ 631 1261 2022
2 0~ o 0 3 191 648 1293 2046
3 0 0 0 3 197 658 1325 2070
4 0' 0 0 3 207 668 1345 2083
5 0 0 0 3 213 684 1364 2099
6 0' 0 0 3 215 698 1382 2119
7 0 0 0 3 221 718 1408 2141
8 0 0 0 10 239 742 1430 2167
9 0 0 0 17 259 767 1449 2193
10 o 0 0 17 278 793 1469 2217
11 0 0 0 17 295 821 1495 2242
12 0 0 0 18 309 849 1523 2268
13 0 0 0 20 320 871 1552 2294
14 0 0 0 25 323 894 1584 2322
15 0 0 0 31 338 918 1614 2344
16 0 0 0 37 346 944 1637 2372
17 0 0 0 42 351 977 1661 2393
18 0 0 0 43 -360 1003 1687 2413
19 0 0 0 43 382 1020 1707 2441
20 0 0 0 45 402 1030 1721 2467 *
21 0 0 2 46 422 1043 1736 2483
22 0 0 3 52 446 1059 1753 2502
23 0 0 3 59 468 1081 1767 2520
24 0 0 3 65 490 1105 1790 2538
25 0 0 3 75 510 1119 1819 2563
26 0 0 3 88 522 1135 1849 2590
27 0 0 3 104 528 1147 1877 2616”
28 0 0 3 120 546 1164 1909 2646
29 0 0 3 144. 565 1192 1935 2668
30‘ o 0 3 167 587 1228 1965 2693
31 0 0 3 167 609 1228 1992 2711

Huv - V. n s nov‘ “0‘ 1
APPLUDI},LIII Date, degree-days 1ron oases 42 r and 40 r and accumulated
days from April 20 and at each sampling time for wheat and

oats at Gull Lake (1970).

 

 

 

 

Date Degree - days Days from
Gull Lake 1970 base 42°F base 48°F April 20
April 23 121 59 w 3
April 29 25;\\ 144 9
May 6 ' 542 ' 215 1 6
May 13 487 320 23
May 20 608 402 30
May 2 835 565 39
June 5 986 684 46
June 12 . 1,193 849 . 53
June 18 1,333 1,003 59
June '25 1,540 1,119 ' 66
July 6 1,859 1,382 - 77
July 14 2,119 1,584 ’85

J41? 22 A 2.336 1.753 93

 

 

APPZIIDIX IV Date, degrc

(J

3 ' P 1hr” .7.
laws iron sanes 41

071

o
- and 43 F and accumulated

days from April 20 at each sampling date for wheat and oats

at East Lansing (1970).

 

Date

 

Degree - days Days from

base 42°F base 48°F April 20'
May 8 411 259 19
May 14 532 347 25
May 19 622 411 30
May 22 699 470 33
Kay 23 313 550 39
June 4 975 671 4U
June 11 1,168 822 53
June 18 1,375 987 60
June 25 1,517 1,090 67
July 1 1,685 1,222 73

 

"‘fl

 

 

 

ll‘l'lll‘lllllll‘l'l‘lf .

Appendix V. Total biomass of foliage (g. per sq. ft) of winter wheat
and spring oats collected for cereal leaf beetle population
density estimates (n=30:§.E.).

 

Date Degree-days Wheat Oats
(base 42°F) Gull Lake (R-Area)

 

5/5 338 4.35:0.18

5/13 487 7.82:0.37

5/18 554 11.0710.63 0.36:0.03
5/22 664 16.01:p.62 0.87:0.08
5/28 800 27.75:1.32 2.43:0.19
6/4 964 34.9912.01 6.26:0.39
6/10 1125 44.82:}.83 ll.44:p.56
6/17 1351 54.98i2.90 14.35:1.04
6/24 1540 54.97:2.14 25.83:1.05
6/30 1679 52.30:?.80 24.08:1.25

 

Appendix VI. Total biomass of foliage (g. per sq. ft.) of winter
wheat and spring oats collected for cereal leaf beetle
pepulation density estimates (n=30; :§.E.)

 

 

Date Degree-days 'Wheat Oats
(base 42°F) Gull Lake (T-Area)

5/7 352 2.10:0.15

5/13 _ 487 3.92:0.38

5/18 554 4.65:0.32 . 0.83:0.10
5/22 664 6.45:0.57 1.52:0.19
5/28 800 12.68:p.81 3.57:0.24
6/4 964 15.17:p.94 7.63:0.43
6/10 1125 19.51:1.14 3.18:0.75
6/17 1351 25.85:1.77 20.7210.99
6/24 1520 28.70:1.99 26.55:2.01

6/30 16.79 20.18:2.12 31.61:2.76

Appendix VII. Total biomass of foliage (g. per sq. ft.) of winter wheat
and spring‘oats collected for cereal leaf beetle
population density estimates (n=30; :§.E.)

 

 

Date Degree-days Wheat Oats
(base 42°F) East Lansing (C-Area)

5/8 411 4.05:0.24

5/14 532 6.15:0.51 0.33:0.05
5/19 622 9.87_+_0.65 0.86:0.07
5/22 699 14.96:}.22 1.49:0.14
5/28 813 26.96:1.44 3.39:0.27
6/4 975 38.4611.63 11.60:0.75
6/11 1167 49.14i2.43 22.08:1.20
6/18 1374 71.53:4.44 42.27:?.14
6/25 1516 76.27:3.29 52.04i2.07

7/1i

1684

84.72:3.94

63.93:3.00

Appendix VIII. Cereal leaf beetle egg and larval densities per sq. ft.

in winter wheat and spring oats (n=30; 18.8.)

 

 

 

 

 

—‘ —=====
Degree- Gull Lake (R-area)-197O
days Eggs Ir II III IV
(base '
Date 48°F) WHEAT __
5/7 213 29.17+1.90 0 0 0 0
5/13 320 118.8017.24 0.40+0.11 0.17+0.08 o 0
5/8 360 95.20?5.71 2.73?0.37 0.60?0.22.- 0.03+0.03 0
5/22 446 82.66?6.24 17.6211187 7.21:1.20 0.17:0.09 0
5/28 546 36.03¥3.10 4.10:0.71 12.27?l.30 12.4012.12 3.17+l.07
6/4 668 9.87?1.71 4.80?0.56 8.80?0.93 11.1010.9l 14.93:1.65
6/10 767 0.63:0.31 0.79:0.22 3.97:0.68 8.83}1.04 l4.60§1.56
6/17 977 " " 0.03E0.03 0.73:9.18 2.90:0.48
OATS
5/18 360 25.77+3.01 0.03+0.03 0 0 0
5/22 446 70.10?5.89 1.69:0.42 0.34+0.12 o 0
5/28 546 91.71?9.87 10.71?1.30 7.79:1.43 3.36:0.93 0.07:0.05
6/4 668 86.47?5.96 23.2712.09 25.00?2.18 12.9012.08 3.93:1.25
6/10 767 l2.40¥2.05 9.8771.77 18.87?1.87 18.33:1.92 18.13:}.69
6/17 977 0.4810.14 l.1310.43. 6.70:1.21 11.87:1.26 22.93:2.90
6/24 1105 0' 0.37?0.10 0.90?0.19 3.00:0.49 5.40:0.60
6/30 1228 0.23:0.18 0.03Ep.03 0.173p.08 0.20:0.09 0.2oip.07

 

Appendix X. Cereal leaf beetle egg and-1arva1 density per sq. ft. in

winter wheat and spring oats (n=30; $5.3.)

 

 

 

 

 

Degree- East Lansing (C-area)-l970

days Eggs I II III IV

(base
Date 48°F) WHEAT
5/8 259 2.43+0.38 0 0 0 0
5/14 347 8.17:0.91 0 0 o 0
5/19 411 15.4731.38 0.13+0.06 0 0 0
5/22 470 12.63+1.69 0.43?0.20 0.27+0.13 0.0319.03 0 I
5/28 550 6.47:0.98 1.33:0.23 0.5310.16 0.1010.06 0.03+0.03 "
6/4 671 3.4310.66 1.2710.19 1.8010.37 1.1010.23 0.27Ib.03 1
6/11 822 0.40?0.25 0.40?0.14 1.1010.30 1.73+0.64 3.37?0.81 ‘4
6/17 962 0.0710.07 0 “ 0.07?0.05 0.43?0.13 4.13?2.53
6/18 6' 0 0.13350 . 06 0.203040 0. 37350.11

OATS

5/14 347 1.90+0.33 0 0 o 0
5/19 411 4.9010.91 0 0 0 0
5/22 470 38.33?2.44 0.23:0.14 0 0 0
5/28 550 36.30?3.92 1.03+0.30 0.40+0.15 0 0
6/4 671 34.0713.89 8.0310.94 7.18?1.42 1.73:0.40 0.13:0.06
6/11 822 8.37?1.16 3.0310.56 5.4010.77 l0.00:1.17 11.83:}.47
6/17 962 2.1710.37 1.00?0.22 1.83:0.31 3.97:0.53 8.93:0.91
6/18 0.13?0.08 1.37:0.39 2 8710.52 3.17:0.47 4.60:0.84
6/25 1090 0.50Ep.18 0.53ED.16 1.13Ep.22 2.30:0.48 1.73+0.32

Appendix IX.

-102.-

Cereal leaf beetle egg and larval densities per sq. ft. in

winter wheat and spring

oats (n=30; :§.E.)

 

 

 

 

 

 

Degree- Gull Lake (T-area)-1970
days Eggs I II III IV
(base
Date 48°F) WHEAT
5/1 187 32.20+2.58
5/13 320 81.7016.88
5/18 360 103.27?8.45 7.67+1.05 0.90+0.29
5/22 446 115.63?8.46 17.1072.05 24.47?2.17 2.67:0.59
5/28 546 48.60?5.04 13.2711.70 23.30?2.25 26.90i3.48 7.47+1.67
6/4 668 9.86?3.10 6.45?1.73 10.1011.37 19.76+l.92 l7.45¥1.92
6/10 793 0.77?0.30 0.53?0.15 5.13?1.22 9.43E1.08 15.9011.84
6/17 977 0.0730.05 0.0330.03 0.0730.07 0.57:0.19 1.93Ep.44
OATS
5/18 360 35.17+2.77 0.07+0.05
5/22 446 150.07110.74 3.5010.46 1.07:0.22
5/28 546 176.55?12.36 23.14?2.30 l3.45+1.98 2.62:0.73 2.17:1.17
6/4 668 139.97111.68 27.03?2.70 44.43?3.61 17.4712.33 4.57:0.85
6/10 793 33.3715.17 26.23?3.96 37.7013.67 23.4712.16 18.63i2.30
6/17 977 1.63?0.74 4.5010.98 10.2711.50 15.47:1.38 23.23:2.30
6/24 1105 0.67:0.41 0.13?0.06 1.73?0.40 4.9010.73 5.50:0.80
6/30 1228 0.20}0.12 0.03Ep.03 0.1030.07 0.27:0.10 0.83:9.20

 

0 I i I I I i l I ll ll Il-III Ill l ..I' I II" I

-103-

Appendix XIa. Date, accumulated degree-days (base 42°F) and the
number of eggs per 2 linear feet of row in winter
wheat at 2 sites at Gull Lake (n=10; :§.D.)

 

 

 

*Samples taken on different days

E 3

Date Degree-days . Number of eggs in wheat
(base 48°F) Gull Lake R Gull Lake T

5/5 213 22.2:10.0 27.8:12.7

5/7 . 221 11.1: 6.7 10.8:_6.1

5/13 320 66.5:15.8 47.0:18.4

5/18 360 34.6:12.4 43;2:13.2

5/21 422 41.8:_8.6 38.7:14.2

5/26 522 41.4:12.8 35.5113.1

5/28 546 22-5:.9-7 12.9: 7.6

6/2* 648 8.5: 5.0

6/8 742 7.5: 6.5 1:6:_l.6

6/18 1003 i 0.0

6/3 658 ' 7.5:3.8

6/15 I 918 0.6:1.1

6/19 1020 0.0

 

lggll!‘

I11 JII‘I (ll '11,! III 'II 11111 I II.
I III Ill-.1 ll' ll Its-113'

Appendix XIb.

Date, accumulated degree-days (base 48°F) and the
number of eggs per 2 linear feet of row in spring oats
at’2 sites at Gull Lake (n=10; i§.D.)

 

 

 

Date Degree-days Number of eggs in cats

(base USOF) Gull Lake-R Gull Lake-T
5/13 320 21.9:10.6 27.0113.2
5/18 360 29.7:21.5 22.3i_9.3
5/21 422 53.5:35.5 111.1:24.5
5/26 522 74.4:20.1 137.5i25.4
5/28 546 27.3:13.6 45.3:16.4
6/2* 648 207.3:63.6
6/5 684 36.9:16.3 85.4:37.7
6/9 767 25.3:11.4 47.8:16.7
6/12 849 16.8:_5.8 16.9:_6.2
6/15 918 7.5: 4.0 5.1: 4.8
6/19 1020 1.5:_1.5 0.2:_0.6
6/3 658 90.1146.1

 

*Samples taken on different days

Appendix XIc. Date, accumulated degree-days (base 48°F) and the number
of eggs per 2 linear feet of row in winter wheat and
spring oats at Collin's Road, Fast Lansing, Michigan
(n=10;':S.D.)

 

 

 

 

Date Degree-days Number of eggs
(base 48°F) Wheat-C Oats-C
5/8 259 2.6:2.5 -
5/14 _ 347 11.5:6.1 2.612.8
5/19 411 10.8i7.5 . 4.515.1 1
5/22 470 12.415.9 32.8:16.4 J
5/26 534 18.519.3 34.3:15.01
6/3 662 ' 9.7:§.5 46.5:23.2
6/10 794 2.4:1.5 20.2:_8.9
6/15 904 0.0 9.6:9.2

6/18 987 0.1:0.3 1.0:1.5

"I7'11141111111111111“