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LIBRARY “V"

Michigan State
University

    
   

THESIS "
31"

ABSTRACT

THE BIOLOGY AND CONTROL OF
NEPTICULA SLINGERLANDELLA KEARFOTT

ON TART CHERRIES IN MICHIGAN

by Ruediger Carl Hillmann

Body of Abstract

A biological study of Nepticula slingerlandella Kearfott,
a serious leaf miner of Mbntmorency tart cherry, Prunus cerasus
L., was conducted in Michigan during 1966 and 1967.

Adult moths emerged during late—bloom and petal-fall
of the host. The adult population contained.primarily males
during the first week of emergence; however, at the time of
peak adult activity the sex ratio was 1:1. Adult longevity
averaged ll days. The mean fecundity was 17.9 eggs per female.
Egg incubation averaged 16 and 19 days under field conditions
and ll days in the laboratory at 80 F.

Four larval instars were determined by head capsule
measurement and supplemental larval development observations.
Indications of larval and pupal parasitism were noted.

Additional host plants confirmed in.Nfichigan were plum,
Erunus domestica L., sweet cherry, Prunus avium.L., pin, red,
or fire cherry, Prunus pennsylvanica L., and.peach, Egunug
persicae L. Mining could not be induced on wild black cherry,

Prunus serotina Ehrh.

Ruediger Carl Hillman

Chemical control studies were conducted in l96h, 1966
and 1967. Several insecticides gave excellent control.
The application of pesticides at petal-fall followed by a
first-cover spray 10 days later for control of the adult was
the preferred treatment. First-and second-cover sprays against

eggs and larvae also gave good control.

THE BIOLOGY.AND CONTROL OF
NEPTICULA SLINGERLANDELLA KEARFOTT

ON TART CHERRIES IN MICHIGAN

by

Ruediger Carl Hillmann

A THESIS

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

MASTER OF SCIENCE

Department of Entomology

1967

ACKNOWLEDGMENTS

The writer wishes to express his appreciation to his
major professor, Dr. A. J. Howitt. His encouragement, patience
and financial support added incentive toward completion of this
research.program.

Special thanks go to Dr. Paul H. Wboley, who became the
writer's major professor in Dr. Howitt's absence, for guidance
in the final completion of this thesis.

The writer's sincere gratitude is extended to
Drs. Gordon.E. Guyer, James E. Bath, and JOhn H. Hart for
serving on his guidance committee.

The writer is grateful to colleagues Paul E. Boldt and
Richard F. Gertz for their assistance in the collection of data.
Special thanks, also, to technicians Al Pshea and Ian Richards
for their help in carrying out the chemical control experiments.

A special award of appreciation (Ph.T.) to my wife, Julia,
whose love, patience and humor were so important on innumerable
occasions.

A final thanks to all those persons who have assisted

the writer in any way during this endeavor.

ii

TABLE OF

ACKNOWLEDGMENTS. . . . .
LIST OF TABLES . . . . .
LIST OF FIGURES. . . . .
INTRODUCTION . . . . . .
IDENTIFICATION . . . . .
LITERATURE REVIEW. . . .

NEIERIALS AND METHODS. .

EXPERIMENTS, OBSERVATIONS,

CONTENTS

RESULTS AND

Laboratory Emergence Studies.

Laboratory Behavioral Studies . .

Adult Emergence in the Orchard. .

DISCUSSION.

Orchard Observations of the Adult .

Seasonal Development. . . . . . . .

Longevity, Oviposition and Fecundity Studies.

Rate of Oviposition . . . . . . . . . . . .

Egg Incubation Studies in

Larval Description. . . .

Larval Instars. . . . .

Larval Development. . .

Larval Parasitism . . .

Egg and Larval Survival

Description of the Mine

iii

the

Laboratory.

Page

ii

12
13
29
33
38
NB
h6
h?
N?
51
S2
56
56

iv

Pupal Development. . . . . .

Pupal Survival . . . . . . .

Pupal Diapause . . . . . . .

Alternate Host Plant Studies

Meteorological Studies . . .

Control Studies.

S UMRY O O O O O O O O O O O O 0

LITERATURE CITED. . .

Page
58
62
Oh
6h
65
68
75
77

LIST OF TABLES
Page
Table l.-Comparison of blacklight and malaise
traps in sampling adults of Nepticula slingerland-
ella. Lawrence, Michigan. 1966. . . . . . . . . . . 16
Table 2.-Blacklight trap catches of Nepticula
slingerlandella adults. Lawrence, Michigan. 1967. . 17
Table 3.-Elacklight trap catches of Nepticula
slingerlandella adults. Shelby, Michigan. 1967. . . 18
Table h.-Comparison of three colored sticky boards

as traps for N} slingerlandella adults. Lawrence,

 

Michigan, 1967. . . . . . . . . . . . . . . . . . . . 25
Table 5.-Emergence of N} slingerlandella as

determined by four ground cages. Lawrence, Michigan.

1967. . . . . . . . . . . . . . . . . . . . . . . . . 27
Table 6.-The percentage of females in samples of

N} slingerlandella adults collected from tart cherry

trees. Lawrence, Oshtemo and Shelby, Michigan

1967. . . . . . . . . . . . . . . . . . . . . . . . . 28
Table 7.-Hourly blacklight catches of N}

slingerlandella adults. Lawrence, Michigan. May 26,

1967. . . . . . . . . . . . . . . . . . . . . . . . . 3O

Table 8.-Fecundity of Nepticula slingerlandella
female moths in leaf cages on tart cherry trees.
Lawrence, Michigan. 1967. . . . . . . . . . . . . .

Table 9.-Fecundity ole, slingerlandella female
moths in branch sleeve cages on tart cherry trees.
Lawrence, Michigan. 1967. . . . . . . . . . . . . .

Table lO.-The fecundity frequency distribution
of 2C branch sleeve cages on tart cherry that
contained recorded numbers of N} slingerlandella
adults. Lawrence, Rfichigan. 1967 . . . . . . . .

Table 11.-Larval instars of Nepticula slingerland-
£112 and corresponding collection dates. Lawrence,
Michigan. 1967. . . . . . . . . . . . . . . . . . .

Table 12.-Air and orchard litter temperature
summation from continuous 2 hr temperature measure-
ments. Oshtemo, Michigan. May 3-29, 1967 . . . . .

Table 13.-The effect of various toxicants on
Nepticula slingerlandella adults. Lawrence,
Michigan. l96h. . . . . . . . . . . . . . . . . . .

Table lh.-The effect of various toxicants on
Nepticula slingerlandella eggs and larvae.

Lawrence, Michigan. 1966. . . . . . . . . . . . . .

Table 15.-The effect of several insecticides on
Nepticula slingerlandella eggs and larvae.

Lawrence, Michigan. 1967. . . . . . . . . . . . . .

Page

N1

hi;

AS

53

67

69

71

73

LIST OF FIGURES
Page

Fig 1.-Nepticula slingerlandella moth on a tart

cherry leaf. . . . . . . . . . . . . . . . . . . . . 10
Fig 2.-Illustration of an N. slingerlandella

moth . . . . . . . . . . . . . . . . . . . . . . . . 10
Fig 3.-A "Spin-sect" blacklight insect trap used

for adult emergence studies. . . . . . . . . . . . . 1h
Fig h.-The malaise trap used in 1966. . . . . . . 1h
Fig 5.4Emergence curve of Nepticula slingerland-

ella as determined from blacklight and malaise trap

captures of adult moths. Lawrence, Michigan. 1966. 19

Fig 6.-Emergence curve of Nepticula slingerland—

 

ella as determined from two black sticky board

captures of adult moths. Shelby, Michigan. 1966. . 20
Fig 7.—Emergence curve of Nepticula slingerland-

ella as determined from.blacklight trap captures of

adult moths. Lawrence, Michigan. 1967. . . . . . . 21
Fig 8.2Emergence curve of Nepticula slingerland-

ella_as determined from blacklight trap captures of

adult moths. Shelby, Michigan. 1967. . . . . . . . 22
Fig 9.-Seasonal development of Nepticula

slingerlandella in a tart cherry orchard.

Lawrence, Michigan. 1967. . . . . . . . . . . . . . 35

viii

Fig lO.-Seasonal development of Nepticula

slingerlandella in a tart cherry orchard. Shelby,

 

MiChigaIJ-I 1967 O O O O O O O O O O O O O O O O O C
Fig ll.-"Tygon" plastic leaf cage used in
fecundity studies. . . . . . . . . . . . . . . . .

Fig l2.-Fourth instar N} slingerlandella larvae

 

Fig 13.-Head capsule measurements of Nepticula
slingerlandella larvae. Lawrence, Mfichigan.
1966-67. . . . . . . . . . . . . . . . . . . . . .

Fig lh.-Larval stadia of Nepticula slingerland-
giia as-determined.from.larvae collected at
Lawrence, Michigan. 1967. . . . . . . . . . . . .

Fig 15.-Typical mines of Nepticula slingerland-
alga on tart cherry. . . . . . . . . . . . . . . .

Fig l6.-Sequence of host plant damage caused by
Nepticula slingerlandella. . . . . . . . . . . . .

Fig l7.-Sequence of Nepticula slingerlandella
pupal development. . . . . . . . . . . . . . . . .

Fig 18.-Ventra1 View of an overwintering
Nepticula slingerlandella pupa with part of its
case removed . . . . . . . . . . . . . . . . . . .

Fig l9.-Nepticula slingerlandella pupal case

showing the emergence hole of a parasite . . . . .

Page

37

39

AB

50

SS

57

S7

59

S9

63

INTRODUCTION

Infestations of a leaf miner, tentatively identified
as Nepticula g2}, caused severe defoliation in a number of
Mbntmorency tart cherry orchards, Prunus cerasus L. in
southwestern Michigan in 1962.

In l96h, 1966 and 1967 chemical control experiments
were conducted in a one-half acre block of infested tart
cherry trees located near Lawrence, Michigan. An intensive
study to determine the biology of this pest was conducted in
1966 and 1967 at Lawrence, Shelby and Oshtemo, Michigan.

The research objectives were:

1. Identify the insect.

2. Determine the insect's life history, host
range, and distribution in Michigan.

3. Investigate the extent and importance of
natural controls.

h. Determine effective chemical controls.

IDENTIFICATION

Six adults and one wing-slide were sent to Dr. Annette
Braun, Professor Emerita Ohio State University, an international
authority on the family Nepticulidae for identification.
Dr. Braun identified the specimens as Nepticula slingerlandella
Kearfott.

Fifty adults and 12 larvae collected from infested
orchards at Shelby and.Lawrence, Michigan were sent to
Dr. D. R. Davis, who is affiliated with the United States
National Museum. Dr. Davis identified the material as Nepticula
slingerlandella Kft.

Although this insect has no accepted common name, it
is referred to as the "plum leaf miner" by Crosby (1911) and
Slingerland (1909) in New York. It is commonly called the

"cherry leaf miner" in Michigan.

LITERATURE REVIEW

Nepticula slingerlandella was found by Braun (1917) in
Ohio and by Crosby (1911) and Slingerland (1909) near Rochester,
New York.

The adult was described by Kearfott (1908) as follows:
"Nepticula slingerlandella, new species. Expanse 3.5 to 5 mm.
Head and.fronta1 tuft orange, antenna eye-caps and side tufts
white; antenna whitish gray; thorax bronzy black; abdomen light
gray; legs yellowish white, posterior tarsi finely ringed with
black. Fbrewing-Bronzy black with a shiny fascia at outer
third. Cilia and.hind wings light gray."

Braun (1917) stated that the frontal tuft becomes "paler
behind where it merges into the pale ocherous or whitish
collar." In addition she noted the somewhat irrorated texture
of the forewing beyond the fascia.

Crosby (1911) states, "These moths emerge from cocoons
at or near the surface of the ground during the daytime in the
latter part of Mby'and early June. During the day they remain
quietly on the bark of the trunk and larger branches, none being
found on the leaves. Several hundred moths are often found on
a single tree. They gradually decrease in numbers, and about
the middle of June, they disappear."

Crosby (1911) reports the following information about
the egg: "The eggs are attached to the under surface of the

3

h

leaf, usually at the forks of the more prominent veins.

The egg is about 0.3 mm long by 0.2 mm wide, oval in outline,
flattened where attached to the leaf and dome shaped in profile.
The green of the leaf shows through the transparent egg shell,
making it a difficult object to find. The eggs are most easily
located by holding the leaf at an angle in the sun so that the
light will strike it obliquely, when they will be seen as
minute glistening dots." He also states that the time required
for hatching "cannot be far from two weeks."

Crosby (1911) reports that "in hatching, the larva eats
its way out of the eggshell on the underside next to the leaf,
and enters the leaf directly without coming out on the surface."
He continues, "When full grown, the larvae are about one—sixth
inch in length, greenish white in color with the head light
brown. The contents of the alimentary canal show through the
semi-transparent body as a greenish or brownish stripe."

Needham (1928) describes the larvae of Nepticulidae as
follows: "The larvae are slightly flattened with the head
deeply retracted into the thorax. Jointed thoracic legs and
crochets are wanting and locomotor appendages are represented
only by roughened.protuberances. Such.projections are to be
found in pairs on the second and third thoracic segments and
on the second to seventh abdominal ones. Some species are
said to have one or two additional pairs."

Crosby (1911) reports only one generation in New YOrk

State. Braun (1917) reports that a second brood of larvae may

5

be collected in September "farther south" (than New York).

Braun (1917) reports that the larvae of Nepticula have
four larval instars. Lindquist (1962) determined four larval
instars in Nepticula lindquisti Freeman, a leaf miner of birch.

Braun (1917) states that a change in the character of
the mines of Nepticula usually indicates the beginning of a
new instar. "The mine formed during the first instar is very
short, rarely exceeding a few millimeters in length. The large
conspicuous part is made during the last larval instar."

Crosby (1911) describes the mine as a narrow linear
burrow, often tortuous in its early course, that enlarges "into
an irregular ovate blotch about one half inch in length. In
the linear part of the mine the excretement is left as a blackish
streak extending along the center of the burrow; in the blotch
mine it forms a broad, irregular band along the center, but does
not extend to the tip."

Braun (1917) reports that larvae of Nepticula usually
mine "just beneath the upper epidermis, consuming the palisade
layer of cells and in later stages, some of the spongy
parenchyma cells."

Crosby (1911) writes, "when full grown the larva leaves
the mine through a cut in the upper surface of the leaf, falls
to the ground and there constructs a small flattened brownish
cocoon . . . broadly oval and moderately arched, it is about
2 1/2 mm long by 1 1/2 to 2 mm wide, and is usually wider at

one end. It is surrounded by a thin flange formed by the

closely united edges of the two valves of which the cocoon is
composed." He continues, "the pupae is about 2 mm in length,
ovate pointed behind and somewhat flattened. The ventral
surface is brownish yellow, the dorsum greenish. The eyes
are dark colored and the orange tuft on the head of the moth
shows through the pupal skin. On the dorsum of the abdomen are
six transverse interrupted rows of short brownish spines. On
each side of the dorsum is a longitudinal row of wart-like
protruberances each bearing a colorless spine. The anterior
spines are very short and they gradually increase in length
towards the tip of the body. 'When about to transform to the
adult, the pupa works itself partly out of the end of the
cocoon, possibly by the aid of these spines."

Incidence of pupal parasitism was reported by Crosby
(1911). The parasite was a chalcis-fly, Derostenus salutaris
Crosby. The larva of the parasite emerged through a small
round hole in the side of the parasitized.pupa's cocoon. "In
the fall of 1911 the parasites had increased in numbers so that
nearly one half of the cocoons were infested."

Slingerland (1909) and Crosby (1911) state that the
insect attacked both plum and.prune in New YOrk. Both Crosby
(1911) and Braun (personal letter) found mines on apple closely
resembling N. slingerlandella mines on tart cherry. Braun
(1917) reports that the insect mined wild.plum, Eggggs americana,

and occasionally sweet cherry, Prunus avium L.

A number of Nepticula species closely resembly N. slinger—
landella, either in the external appearance of the adult or in
the hosts attacked by the larva. Braun (1917) in her disserta-
tion on the family Nepticulidae describes the following species:
N. bifasciella, Clemons, which Dr. Braun considers to be identical

to both N .? prunifoliella and N. serotinaella, mines wild black

 

Prunus serotina, and occasionally wild plum, N. americana.
Another species, N. rosaefoliella Clemons, is a leaf miner of
various species of rose.

Crosby (1911) describes a European species, N. gagicolella

 

Stainton, which is closely related to N. slingerlandella, that

 

feeds on cultivated plum. Lindquist (1962) published a life

history of a birch leaf miner, N. lindguisti Freeman, the adult

 

of which resembles N. slingerlandella very closely.

 

MATERIAL AND METHODS

Areas in four commercial tart cherry orchards were
secured for this study. A l/2-acre block near Lawrence (Van
Buren County) was employed for intensive biological studies in
1966 and 1967. Preliminary chemical control studies had been
conducted in this orchard in 196D. An 8-tree block near
Shelby (Oceana County) was used in 1966, but studies were
discontinued in 1967 because small numbers of N} slingerlandella
were found at that time. Another Shelby block, consisting of
35 trees, was used in 1967. An Oshtemo block (Kalamazoo
County), consisting of 30 trees, contained the lightest
infestation of N. slingerlandella and was used in 1967 only.

Laboratory experiments conducted at East Lansing were
concerned with adult emergence, behavior, oviposition, egg

incubation, larval instar determination and pupal diapause.

EXPERIMENTS, OBSERVATIONS, RESULTS AND DISCUSSION

Laboratory Emergence Studies
To predict adult emergence in the orchard and to secure

adults for positive identification, N, slingerlandella adults

 

(Figs 1-2) were induced to emerge from pupae contained in
orchard litter. Litter gathered at various times was incubated
in rectangular 12 x 1h x 16-inch wooden cages covered with 32-
mesh saran screening. The cages were placed in a rearing room
maintained at 70 F. with 55 to 60% relative humidity. A 2h-
hour photoperiod was supplied by two 80-watt fluorescent tubes.

Two adults emerged on April 12, 1966 from litter that
had been incubated continuously since March 26. By.April 20,
h? additional adults had emerged. .Adult studies in the
laboratory were continued through June 10, 1966 with the use
of fresh litter. This procedure predicted field emergence of
adults very closely. Seven adults emerged in the laboratory
on May 23, 1966 from Lawrence litter incubated on May 21.
Emergence in the Lawrence orchard was confirmed by a backlight
trap catch of 23 adults on May 25.

On April 19, 1967, infested litter from.Lawrence was
incubated in a saran-screened cage and on April 29 three adults
emerged. These data were compared with 1966 data from a
comparable calendar period. An algebraic proportion computation

indicated that emergence would occur at the Lawrence orchard

9

lO

 

 

Fig l.-Nepticu1a slingerlandella moth on a tart
cherry leaf.

 

 

Fig 2.-Illustration of a Nepticula slingerlandella
moth. (From Crosby, C. R. 1911. Cornell Univ.
bulletin 308)

11

on May 11. Emergence at Lawrence was confirmed with a
blacklight catch of five males on May 1h. Adult emergence
in the field, therefore, may be predicted with reasonable
accuracy from emergence induced in the laboratory.

To ascertain if light affected adult emergence, litter
was placed in six l-quart, cylindrical cardboard containers
with tight-fitting lids and incubated in the rearing room.
Containers were checked daily for adult emergence. Emergence
within these dark containers closely paralleled the emergence
that took place in the lighted saran-screened cage.

Crosby (1911) stated that the moths emerge during the
daytime. While this is true, the fact that emergence took
place in dark containers indicates that the moths may also
emerge at night.

Field emergence data for 1966 indicated a 3-week lag
in adult emergence between Lawrence and Shelby. To determine
if such a lag would occur under laboratory conditions, litter
gathered on April 18, 1967 at Shelby and on April 19, 1967 at
Lawrence was placed in adjacent saran-screened cages in the
rearing room on.April 20. Emergence from the Lawrence litter
occurred on.April 29; emergence from the Shelby litter did not
occur until 16 days later. Pupation at Lawrence occurred 2 to
3 weeks earlier than at Shelby in 1966. This may have influenced

the time of adult emergence in 1967.

12

Laboratory Behavioral Studies

A seedling Mbntmorency tart cherry tree was placed in
the greenhouse in April 1966 under conditions of natural
photoperiod to study the behavior of the adults and determine
whether they required nourishment. In addition, the tree
provided an opportunity to confirm.the formation and development
of leaf mines. Two branches, were each enclosed in a separate,
6-inch cylindrical saran screen (32 mesh) cage 18 inches high,
fitted over a clay pot containing sterilized greenhouse soil.
The pots were placed in individual saucers filled with water.
One cage was equipped with an internal sucrose dispenser,.
consisting of a small wad Of cotton that was saturated daily
“with sucrose solution. In addition, this cage was equipped
with a continuous water dispensing device. One end of a 3-inch
wide cotton strip l-foot long was placed in a container of
water. The remaining 6 inches were taped to the exterior of
the cage and water was allowed to move upward by capillary
action. The other cage lacked these water and nourishment
devices. Adults that had emerged in the rearing room were
introduced into both cages. Adults in the cage without added
nourishment died within 2 to 3 days, probably from desiccation
rather than from lack of nutrients since the adults normally
feed on leaf glands. Several adults in the other cage were
still active after 1h days. Leaf mining occurred in both
trials indicating that oviposition may occur within 2 to 3 days

after emergence.

13

Adult Emergence in the Orchard

 

A 15-watt "Spin-sect" blacklight insect trap (Fig 3),
manufactured by Ampsco Corporation, Columbus, Ohio, was
erected in each of the test blocks to determine adult
emergence in the orchard and to measure adult activity.
Blacklight traps were placed in Lawrence in 1966 and.l967 and
in the Shelby and Oshtemo blocks in 1967. Each light was
firmly fastened to a cherry tree approximately h feet above
ground level. In 1966 electrical power was supplied by a 12-
volt battery, which was charged daily, whereas in 1967 the
lights were connected directly to llO-volt electrical outlets.
Insects were collected daily from the traps throughout the
season.

To determine the time of adult emergence in 1966 in
the Shelby area two flat black planks 2 inches thick and 12
inches sq were coated with "tangle-foot" and suspended 3 feet
above ground level in two cherry trees in the Shelby orchard.
Insects were identified and removed from the boards twice
weekly.

The malaise trap (Fig h) was used during the 1966
season at Lawrence. The trap was approximately 7 ft high and
h ft sq. The collection device consisted of a screen and
plastic funnel at the top of the trap connected to a collection
jar containing alcohol.

In 1966 the insects were attracted by the black portion

of the trap; thus, in 1967 a trap consisting entirely of black

 

 

 

 

Fig 3.-A "Spin-sect" blacklight insect trap used
for adult emergence studies.

\ ' -
' .l a
0‘ .. _, (“tug
\ A . »- ‘v
.5"
.C

évii’i; ' 1.,“
'., .D. I, fl!
.. {Sn
0
A'

:j I. .1 ~
a.” .
1,4

V‘ . 4" >1"; ' '.
" "L{\~ 94 t
-» "a .
..‘

. a." -. .
‘9. .- g .
'1 t f? I 1.. t'r’ '

WI".

’7‘ .I.A' ‘1 . '.I “'\

5.9“"- . ,
; ‘ 7 ,' .ml'
3;ng
431““: f, gs

! R

 

I V' \
o.’ g .s‘

 

Fig h.-The malaise trap used in 1966. The trap
used in 1967 was completely black with an opaque
collecting device in.place of the screen and plastic
one shown above.

1S

material and utilizing an opaque collection device connected
to a l-quart jar containing alcohol was used. The interior of
the trap became extremely hot during periods of sunlight.

To correct this problem a large white sheet was placed over the
upper half of the trap. This trap did.not capture any

‘N. slingerlandella adults in 8 weeks of operation.

The emergence curves develOped for N} slingerlandella
are presented in Fig 5, 6, 7 and 8. Daily catches are given in
Tables 1, 2 and 3. Large daily blacklight samples were carefully
divided into equal sub-samples, each of which contained at least
100 N} slingerlandella adults. The sub-samples were taken by
evenly spreading the complete sample within a h-in. square
(16 sq. in.) drawn on a 12 x 16 in. sheet of bristle board.

The 16 sq. in. area was sub—divided into four smaller squares
of h sq. in. each (2 x 2 in.). One of the latter was again
subdivided into four l-sq. in. units (1 x l in.). Therefore,

a grid system was constructed whereby the complete sample could
be divided into halves, quarters, eights, and sixteenths.

Since it was decided that each sub-sample should contain at
least 100 N. slingerlandella adults the area counted was
governed by specimen density. Successively larger grids were
counted until at least 100 individuals had been enumerated.

The number and sex of adults in a sub-sample was multiplied by
the inverse of the sub-sample fraction to arrive at a complete
sample count, which is the number reported. For example, a l/h

sub-sample that contained 100 adults would be reported as a

16

Table l.-Comparison of blacklight and malaise traps in

sampling adults of Nepticula slingerlandella. Lawrence,

 

Michigan. 1966.

 

 

 

 

 

 

No. of Adults No. of Adults
Malaise Malaise
Date Blacklight trap . Date Blacklight trap
May 2h 0 0 June 11 72 5
25 23 3 12 1m 2
26 9 2 _ l3 l6 0
27 22 , 5 71h 2 trap
. removed
28 0 O 15 8
29 -a ” s 16 -a
30 -a 8 17 u
31 _a 9 l8 0
June 1 18 2 4 19 39
2 82 10 2O 10
3 79 1h 21 8
h 25 ~ 2 22 O
5 _ 133 7 23 19
6 301; 1b 2b 7
7 L; 2 25 3
8 h0 3 26 0
9 16 5 7 27 1
10 0 10 28 0

 

ano samples taken this date

17

Table 2.-B1acklight trap catches of Nepticula slingerlandella

adults.

Lawrence, Nfichigan.

 

1967.

 

 

No. of Adults

No. of Adults

 

 

 

 

Date Total 3 0” 18:11-8 Date Total 9 3:11:21

May 13 O O 0 O May 29 139 18 109 12
1h 5 0 h 1 30 h2h nu 360 2O
15 1 0 1 31 356 72 28h O
16 7 0 5 2 June 1 1520 368 1088 88
17 52 0 N8 8 2 788' 1ND 626 28
18 13 1 12 0 3 258a 736 1520 288
19 3 0 3 O u 220 56 1th. 20
2O 21 0 20 1 5 132 N2 80 10
21 1h 1 13 0 6 326 18h 118 6D
22 32 1 31 0
23 10 1 9 0 8 16 8 8 0
28 110 11 82 17 9 9 6 3 0
25 108 38 SS 19 10 2 1 1 0
26 1057 159 807 91 11 1 1 0 O
27 153 ho 137 16 12 0 0 0 0
28 66 5 S? h 13 0 0 0 0

 

aNon-det. = Sex could not be determined.

18

Table 3.—Black1ight trap catches of Nepticula slingerlandella

 

 

 

 

 

 

adults. Shelby, Michigan. 1967.
No. of Adults No. of Adults

Date Total $ cf‘ 8:278 Date Total 9 182278

June 1 0 0 0 0 June 21 1N6 1N 126 6
2 2 O 2 0 22 103 N 92 7
3 0 0 0 0 23 736 208 NNO 88
N 2 0 2 0 2N 77 29 N2 6
5 1N 0 1N O 25 108 22 80 6
6 3 O 3 O 26 8N 16 66 2
7 0 0 0 0 27 16N 58 100 6
8 3 1 2 0 28 120 N2 63 15
9 19 1 15 3 29 226 50 152 2N
10 8 2 5 1 3O 27N 50 25N 20
11 33 0 31 2 July 1 70 16 NN 10
12 5 O N l 2 l7 7 9 l
13 76 7 SN 15 3 26 1 2N 1
1N 53 8 31 1N N 63 22 N1 0
15 178 16 1N9 13 5 11 8 3 0
16 500 28 3NN 128 6 56 18 38 0
17 336 12 288 36 7 NN 9 35 O
18 22 N 1N N 8 16 6 10 0
19 202 1N 16N EN 9 7 N 3 O
20 5N1 32 N81 28 10 0 0 0 0

 

aNon-det. = Sex could not be determined.

Number of adults

19

 

 

 

  

600
500-
— Blacklight
-... _ Malaise trap
400
300

200

 

IOO

 

 

 

 

 

 

 

ho

a -. "a 3

Week ending

'0

Fig 5. —Emergence curve of Nepticula sliggerlandella as
determined from blacklight and malaise trap captures of

adult moths. Lawrence, Michigan. 1966.

 

cola -

Number of adults

20

 

30*-

 

 

 

 

 

 

 

 

 

 

_6__ 7

25 2
Week ending

0H
6H
N

01'"

.6.
l8

Fig 6.-Emergence curve of Nepticula slingerlandella as
determined from two black sticky board captures of adult

moths. Shelby, Michigan. 1966.

Number of adults

21

 

 

 

I0,000 :-
E Total
9 ---9
0l
_ / \
IOOOE / \\
C x, \
_. l \
_ / \
.. ’9’ ‘l
I \\
|()C):7 I
E: I \
I I \
I I \
I \
' I, \
\
IO -
: I
I I \
Z I
.. [I
I I
I I 1 11, l
.9. .Q .6. .1 .5. 9.
I3 20 27 3 no I7
Week ending

Fig 7.-Emergence curve of Nepticula slingerlandella
as determined from blacklight trap captures of adult

moths. Lawrence, Michigan. 1967.

Number of adults

2000

|000

IOO

22

 

I

 

 

- \
I
I \\
: / \
: 2 (i
_ I \
l- I \
_. I \
II \
E I \\
- I
_. c: \
—. l’ (O
r [I \
I I I I I I I
2 2 E 2. .9. l .7. l l
27 3 no I? 24 l 3 I5 22
Week ending

Fig 8.-Emergence curve of Nepticula slingerlandella
as determined from blacklight trap captures of adult

moths. Shelby, Michigan. 1967.

23

whole sample count of N00 adults for that date.

Although adults may be collected for a period of 6 to
8 weeks in orchards infested with N} slingerlandella, peak
flight occurred within 2 to 3 weeks after initial emergence
after which the numbers of adults declined.rapidly. Females
emerged 1 week later than the males, peaked simultaneously with
the males and probably outnumbered the males in the last half
of the adult activity cycle. The light trap samples contained
a majority of males throughout the sampling period because of
the male swarming behavior at daybreak. The preponderance of
males early in the emergence cycle enhances the probability
that copulation will occur soon after female emergence.

The lower peak observed at Lawrence in 1966 (Fig 5) is
probably due to insufficient power being supplied by the
battery. The Shelby population lags 2 to 3 weeks behind that
at Lawrence. The graphs also indicate the annual environmental
variation that affects the time of insect emergence. Emergence
at both locations, in both years, occurred during late bloom
and petal fall. While the calendar emergence dates vary
considerably, there is agreement between emergence and
phenological development of the tree.

A single generation per year is beneficial to this
species, since the majority of any second brood would.perish
from starvation. The first brood causes such extensive
defoliation that little foliage is left for any prospective

second brood. In addition, the leaf glands, from which the

2N

adults derive much of their nourishment, dry up after the leaf
matures (Reinke 1876 in Esau 1953). Thus, any second generation
adults would be subjected to very adverse conditions.

To determine if other types of insect traps were effective
in capturing N} slingerlandella, a dozen sticky boards of three
different colors were tested at the Lawrence block. Single
black, green and yellow sticky boards measuring 1 x 8 x 10 inches
were suspended about N ft above ground level in each of four
trees selected at random throughout the Lawrence orchard. They
were positioned approximately equidistant from each other
around the tree. The number of trapped N. slingerlandella
adults was recorded weekly (Table N).

Although there is considerable variation between
replications, the green sticky boards trapped more insects than
the other two colors combined. 'With a single exception, peak
catches were recorded.for all color trials by May 30.

It is likely that the boards are not sufficiently
precise to warrant their use for experimental purposes. However,
the green-colored boards are satisfactory as a base for the
timing of chemical applications for control of N} slingerlandella.
From a practical standpoint, the phenological development of the
host is a sufficiently accurate guide upon Which to base
commercial control.

A study was initiated to determine the sexual pattern
of adult emergence in the orchard. Four ground cages, one,

36 x 36 x 36 inches and the other three, 16 x 2h x 20 inches,

Table N.—Comparison of three colored sticky boards as

traps for N} slingerlandella adults.

25

Lawrence, Michigan.

 

 

 

 

 

1967.
No. of N} slingerlandella
recorded on specified date
Color Seasonal
Tree of Board 5/16 5/22 5/30 6/5 6/lN 6/21 Total
A Black 1 18 79 N3 0 O 1N1
Green 0 65 N00 65 l 0 531
Yellow 0 8 llN 53 0 0 175
B Black 0 O 30 1N 1 0 NS
Green 0 2 250 37 0 0 289
Yellow 0 1. N5 15 2 O 63
C Black 0 3 178 21 O O 202
Green 11 32 610 32 1. 0 669
Yellow 0 1 lON 5N 0 0 159
D Black 0 0 N3 35 N 0 82
Green 0 1 31 17 8 0 57
Yellow 0 1 N7 1N7 17 O 212
Total Black 1 21 330 113 5 0 N70
Green N 100 1281 151 10 O 17N6
Yellow 0 11 310 269 19 0 609

 

26

were placed open end down at random under trees to trap adults
as they emerged. The adults that emerged in these cages were

sexed and recorded (Table 5). 'While males predominate during

the early emergence cycle, females emerge in sufficient number
to balance the sex ratio and predominate during the last half

of the adult activity period.

Adults that had been periodically collected at random
in the orchard were sexed to determine the changing seasonal sex
ratio under orchard conditions at Lawrence (Table 6). 'While
these data showed a trend similar to that shown by the ground
cages, the sex-ratio changes appear to be a week behind the
changes shown by the ground cages. The tree samples represented
the total N} slingerlandella population present in the orchard,
while the ground cage data represented only the emergence that
had taken place within the sample interval.

Field-collected adults were sexed on consecutive days
in similar areas in Oshtemo (Table 6). The data demonstrate the
great variation in the sex ratio that may occur in a short
interval of time. Field-collected adults were sexed on only 1
day in Shelby (Table 6) and as in Lawrence, males predominated
during the first half of the emergence period.

The blacklight trap is the most effective method for
sampling field activity of this insect. The ground traps
sample the current adult emergence more effectively because
samples are unaffected by previous emergence. The area sampled,

however, is much more limited.

27

Table 5.-Emergence of N} slingerlandella as determined

by four ground cages. Lawrence, Michigan. 1967.

 

 

 

 

 

Total Adults Male Female

Date Trapped Number 7' Number

May 2N 99 63 63.7 36 36.3
26 228 152 66.7 76 33.3
28 2N6 128 52.0 118 N80
30 1N3 63 NN. 0 80 56.0
31“1 33a 10 30.3 23 69.7

June lN l -- -- 1 100.0

 

aFrom large ground trap only.

28

Table 6.-The percentage of females in samples of

N} slingerlandella adults collected from tart cherry trees.

 

Lawrence, Oshtemo and Shelby, Michigan. 1967.

 

 

 

Date No. of Adults % Females
Lawrence

May 19 N8 12.5
21 100 15.0
22 106 21.7
2N 97 15.5
26 123 28.5
31 50 No.0
am

May 2N 82 17.1
25 167 37 .1
Shelby

June 20 125 32.8

 

29

Orchard Observations of the Adult

 

To analyze the nocturnal behavior of N} slingerlandella,
adult insects were collected hourly from the light trap at
Lawrence from 8 PM through 6.AM on May 26, 1967. The temperature
ranged from 61 to 68 F.

A relatively high number of females was caught between
8 and 10 PM (Table 9). These females became active soon after
dusk, left their resting places at the base of the tree trunk,
and began their nightly migration up the tree past the blacklight.
The number trapped declined after 10 PM since the majority of
adults were in the upper branches beyond the range of the black-
light.

The heavy concentration of males occurred between N AM
and daybreak when the males became very active and formed a
mating swarm. Many'were attracted to the blacklight and
consequently all seasonal blacklight samples, with the exception
of a few collected at the end of the adult activity period,
showed a preponderance of males.

It would have been desirable to operate the light trap
for two additional hours. It is likely that the insect count
would decline rapidly between 6 and 7.AM then drop to near 0,
since many adults are mating and the remainder are resting
quietly on the trunks of cherry trees.

Field sexing was based on abdominal shape; the females
have a thick sausage-shaped abdomen, while the males have a

much thinner funnel-shaped abdomen. Laboratory sexing may be

30

Table 7.-Hourly blacklight trap catches of N. slingerlandella

adults. Lawrence, Michigan. May 26, 1967.

 

 

No. of adults caught

 

 

Hour
Total 9 o" Non-det . a
8-9 PM 91 33 N8 10
9-10 61 32 25 N
10-11 18 7 10 1
11-12 N3 9 2N 10
12-1 .AM 18 5 10 3
1-2 13 2 9 2
2-3 28 5 22 1
3-N 16 l 13 2
N-5 391 N2 320 29
5-6 378 23 326 29
Total 1057 159 807 91

 

aNon-det. = Sex could not be determined.

31

done by noting the four valve clasper formed by a mesal horizontal
and vertical cleft of the male's posterior; the female has no
readily visible external genital organs.

Adult behavior patterns were observed on numerous
occasions in the field. The adult moths became active at dusk
and by a series of short irregular flights began a migration
from the base of the trees toward the upper branches. Adults
were found.primarily on the lower leaves between 8 and 10 PM.

By midnight they were spread throughout the tree, although a
greater proportion appeared to be in the Upper-half of the tree.

Adults were observed feeding on bits of aphid excrement
on leaves. They also derive nourishment from the leaf teeth
glands and particularly the petiolar glands. Reinke (1876 in
Esau 1953) states that in Nggggs the leaf teeth glands secrete
resins whereas the petiolar glands produce a nectar.

At daybreak the mating behavior began, as the adults
began to swarm in great numbers. Several hundred adults from
the mating swarm were sexed, and all were males. Of N3 adults
resting on cherry trees, 36 were females.

The females must emit a sex attractant, since many males
simultaneously attempted to mate with a single female.
Eventually 1 pair succeeded to copulate and continued to mate
for 2 to 3 hr. Mating usually occurred on leaves, although any
substrate sufficed. 'When mating was completed the pair parted
and the male flew away. The female generally departed after

about 30 sec without ovipositing. 'Within 3 hr after daybreak

32

the adults had returned to the bark at the base of the trees
and remained relatively inactive for the remainder of the day.
The number of times an individual mates is not known.
The dissection of a female indicated a pouch laterally attached
to the oviduct that appeared to be a spermatheca. Therefore, a
single 2 to 3 hr copulation period should yield sufficient sperm
to fertilize all of the female's eggs.
The entire mating procedure was witnessed in a leaf
cage. 'With the pair facing in opposite directions, the male
raised its wings vertically and joined its posterior to that of
the female. The abdomens were not joined mesially. From a
ventral view, the male was joined at the left of center on the
female abdomen. The male then lowered its wings and the pair
copulated.for 2 hr and 19 min. Later examination revealed that
females had asymmetrical genetalia. One opening, the ovipositor,
was located in the center of the posterior. Another opening,
the one used in copulation, was located laterad of the ovipositor.
Many unsuccessful attempts were made to witness the act
of oviposition in the orchard. An adult resting on the under-
side of a leaf was located with the aid of a two—cell flashlight,
then observed under illumination supplied by a one-cell penlight.
The adult was collected with an aspirator when it started to
move to another location. If it was a female, the possible
oviposition site was marked on the leaf. These leaves were
later examined in the laboratory but none showed any evidence

of oviposition.

33

Although oviposition was not observed, it apparently
takes place at night. Evidently the eggs are evenly distributed
throughout the tree crowns, for mining appeared to be uniform
throughout the crowns later.

The behavior of the adults at night may be a guard
against desiccation. Adults under low humidity conditions in
the laboratory died very quickly whereas those under humid

conditions lived for longer periods.

Seasonal Develgpment

To determine the rate of oviposition and to determine
egg and larval development under field conditions, 50 to 100
leaves were selected at random to a height of 7 ft at various
intervals from the Shelby and.Lawrence orchards. The number
of eggs, larvae and vacated mines from these leaves were
recorded.

Estimates of actual field development of N. slingerlandella
are given in Fig 9 and 10. The count on each date for each of
the factors (emergence, hatching, etc.) reported was converted
to a percentage of the total data collected for that factor.
The are Sines of the percentages were graphed on their
corresponding dates, and a line was fitted by eye to best
represent the data.

As shown by the graphs, the time from mean emergence to
mean oviposition was approximately 6.5 days at Lawrence and
10.5 days at Shelby. The time from mean oviposition to mean

hatching was approximately 16 days at Lawrence and 19.5 days at

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Shelby. Mean larval development at Lawrence was completed in

23 days.

Longevity, Oviposition and Fecundity Studies

Leaf cages and branch sleeve cages were used in
experiments in the Lawrence block in 1967 to determine longevity,
oviposition potential, ovipositional rate, and mating behavior

of N} slingerlandella adults. Eighteen individual leaf cages

 

(Fig 11) were fabricated from 3/N inch "Tygon" plastic tubing
cut into 1 l/2-inch lengths. A bent pin-curl clamp was glued
onto the side of each piece of tubing. A piece of thin, clear
plastic, 1 inch sq. was glued on to the free end of the clamp
so that it covered one end of the piece of tubing. A.plastic
foam gasket was glued onto the tubing underneath the plastic
square. A l—inch sq. piece of 32-mesh saran.screen was glued
to the other end of the tubing to allow ventilation. Two holes
were made through the wall of the tubing with a paper punch.
A small cork was placed in one hole, a novacaine vial (one end
of which contained a small cotton.plug) was placed in the other.
The vial was filled'with either distilled'water or a saturated
sucrose solution and was closed with a small red rubber stopper.
The cage was then clamped onto a cherry leaf with the open end
against the underside of the leaf.

For the first series of experiments, each vial was
filled with distilled'water, and a small sugar cube was added

to each cage for nourishment. One male and one female adult

39

 

 

 

Fig ll-"Tygon" plastic leaf cage used in fecundity studies.

NO

was placed in each cage. The cages were checked daily during
the first 2 weeks of operation, followed by a period of 9 days
during which no observations were made. The cage was removed
when the female expired or escaped, and the date of death was
recorded. The leaf was removed from the tree and the number
of eggs on the underside was recorded at a later time in the
laboratory.

A hard rain that occurred 10 days after the cages were
placed in the orchard made the sugar cubes very sticky. Many
weakened adults became entrapped in this sugar and.perished
prematurely. The substitution of vials filled with a sucrose
solution eliminated this problem.

With.prolonged use the tygon plastic became cloudy due
to absorbed.moisture and observation of adults in the cages
became difficult. A few days in a dry environment made the
plastic clear once again.

Eight females and 13 males died in the leaf cages from
natural causes. The males and.fema1es lived an average of 9.N
and 9.6 days, respectively. The range of female longevity was
6 to 13 days, while male longevity ranged from 6 to 16 days.

Fecundity, as determined with individual leaf cages,
is presented in Table 10. Variation in egg laying ranged from
no eggs (10 females) to 82 eggs (1 female). Eight females laid
at least 20 eggs. The mean fecundity was ll.N eggs per female.

The average fecundity as established by the leaf cages

is probably lower than that under natural conditions since the

N1

Table 8.-Fecundity of Nepticula slingerlandella
female moths in leaf cages on tart cherry trees.

Lawrence, Michigan. 1967.

 

 

 

No. of eggs
laid per
Observations female
1 82
1 N7
1 N1
1 29
2 27
2 20
1 19
1 11
3 ' lO
2 9
1 8
2 7
l 6
1 3
2 2
N l

10 O

N2

insect was limited in its mobility and ovipositional sites.
Transferring the cage to a fresh leaf daily would increase the
number of available ovipositional sites, possibly increase the
rate of oviposition, and probably increase the number of eggs
laid per female.

To determine the fecundity under more natural conditions,
25 branch sleeve cages were placed in the Lawrence orchard.
These cylindrical cages, measuring 8 inches in diam and 12 inches
in length, were constructed of 32-mesh saran screen. Cloth tubes
8 inches in diameter were sewn on to each end of the screen to
enable the ends of a cage to be tied around a branch. A N-dram
vial was filled with concentrated sugar solution, stoppered'with
cotton, inverted and fastened to the inside of the sleeve with
a wire harness.

A week before adult emergence occurred five sleeves
were placed on each of five trees selected at random in the
Lawrence orchard; the cages were evenly spaced about N ft above
ground level around each tree. Male and.female adults were
introduced into 20 cages and allowed to oviposit. Five cages
(one per tree) served as checks. Mbst of the adults were
collected from ground cages in the orchard to insure that none
had previously oviposited. Approximately l/N of the sleeves
were stocked.with adults collected from the base of trees
early in the adult emergence period.

Oviposition in the field was assumed to be completed

when adults could no longer be collected. At that time the

N3

sleeves were collected and the eggs counted (Table 9).

The mean fecundity was 17.9 eggs/female with a standard
deviation of 7.N. An approximately normal fecundity
frequency distribution is indicated in Table 10. One sleeve
cage averaged N5 eggs per female. The factors responsible
for this high count are not known.

Fecundity as established by the sleeve cages also may
be lower than the actual field fecundity. The fact that some
females were capable of laying N7 and 82 eggs, as demonstrated
in the "Tygon" leaf cages, indicates that their mean reproductive
potential may be much higher than 17.9 eggs per female. The
average life span in the cages is not known. However, some

adults were alive after 10 days.

Rate of Oviposition

Infested orchard litter, collected 2 weeks before adult
emergence, was stored at NO F prior to being placed in saran
screen cages in the 70 F rearing room to initiate adult
emergence. Unfortunately the prolonged storage period at cold
temperatures, after the pupae had started the spring maturation
process, reduced their viability so that only five female and
eight male adults emerged. A pair of adults was placed in
each of five "Tygon" plastic leaf cages (Fig 11) in an
abandoned tart cherry orchard near East Lansing. The cages
were moved to a fresh leaf each day and oviposition data

recorded.

NN

Table 9.-Fecundity of Nepticula slingerlandella female
moths in branch sleeve cages on tart cherry trees. Lawrence,

Michigan. 19 67 .

 

 

 

Males
Females (approximately) Total eggs Eggs/g

10 25 N50 N5.0
lo 17 270 27.0
10 12 2N2 2N.2
10 13 238 23.8
11 15 221 20.0
10 20 200 20.0
l2 16 239 19.9
ll 17 203 18.5
10 15 18N l8.N

9 15 166 l8.N
10 15 165 16.8
10 20 167 16.7

9 15 132 ' 1N.7
12 15 162 13.5
11 15 lNN 13.1
10 20 127 12.7
10 16 ' l2N 12.5
10 12 122 12.2
10 20 110 11.0
15 15 93 6.2

210 3767 17.9

 

N5

Table 10.-The fecundity frequency distribution of 20 branch
sleeve cages on tart cherry that contained recorded numbers of

N. slingerlandella adults. Lawrence, Michigan. 1967.

 

 

Number of branch sleeve

 

Class intervala cages contained in the
(mean eggs/female) class interval
6-10 _ ~ 1
11-15 7
16—20 8
21-25 2
26-30 1
31-35 0
36-NO 0
Nl-N5 l

 

aDetermined from a formula by Yule in LeClerg (1962). No. of
classes = 2.5\5/number in sample.

N6

Only two females oviposited. One female laid eight
eggs, four each on her third and fourth days in the cage.
The other female laid only two eggs (on her fourth day).
The first female lived 10 days, the second, 8 days.

While the oviposition rate experiment was not entirely
successful, coupled with the seedling tree experiment, it
demonstrated that oviposition is possible within 2 days after
emergence and usually is not completed in 1 day. Oviposition
probably continues at a more or less constant daily rate until
the female dies. In rare cases, field-collected leaves
contained as many as a dozen eggs all deposited in a contiguous
row, obviously extruded by one female. Usually eggs were

deposited individually near a prominent leaf vein.

Egg Incubation Studies in the Laboratory

To determine the hatching time under constant temperature,
10 eggs obtained.from the ovipositional rate experiment were kept
at 80 F until hatching or desiccation occurred. Leaves
containing the eggs were placed in a small jar that contained
nutrient solution. The jar was placed in a N—inch flower pot
and a clear plastic freezer dish was inverted over it. This
material was placed in an 80 F rearing room maintained at a
2N-hour photoperiod which was supplied by three NO-watt
fluorescent tubes. The eggs were examined daily. Of the 10
eggs, four failed to hatch, two hatched on the tenth day,
three hatched on the eleventh day, and one hatched on the

twelfth day. Mean time for egg hatching was about 11 days.

N7

Larval Description

 

The first three larval instars are clear, glistening and
semi-transparent. The last instar is translucent greenish white
(Fig 12). The head capsule, barely visible in the first instar,
takes on a brown coloration as the larva matures. It is
extremely flattened.with a somewhat triangular front and has
two dark dorsal longitudinal lines which meld into an anterior
triangle. From a lateral view, two dark thin lines meet
anteriorly in a V shape. A large dark oscellus is present on
each side of the anterior third of the head capsule.

The larva has three thoracic and nine abdominal segments.
Segmented thoracic legs and crochets are absent. Paired
locomotor protuberances are located on the venter of the second
and third thoracic segments and on abdominal segments one
through seven. The protuberances are apparent on a live
specimen that is in the act of constructing its cocoon. They
are extremely hard to detect on most preserved specimens.

Each segment has two rounded lateral protuberances, one on each
side, which are covered with fine light hairs. The body is
covered with rather long, light colored, thinly dispersed,
lateral and dorsal setae. At hatching, the first instar
averages 0.09 mm in width by O.N6 mm in length. The last

instar averages 0.36 mm in width and N to 5 mm in length.

Larval Instars
To determine the number of larval instars and the length

of stadia, the width of larval head capsules was determined and

 

N8

 

 

Fig l2.-Fourth instar N.‘ slingerlandella larvae.

 

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51

their date of collection noted.

The head capsule widths are reported in Figure 13.
Instars one, three, and four are readily apparent. Head
capsule widths for the first-instar ranged from 0.07-0.11 mm,
for the third-, 0.20-0.26 mm and for the fourth-, 0.31-O.N2 mm.
The second-instar (0.12-0.18 mm), however, has a low count at
0.1N mm which makes it appear as two instars. It is the
opinion of the writer that this low count is a coincidence.
As a larva matured, the body width increased gradually while
the head capsule width remained constant between molts.
A larva that was ready to molt had a relatively small head
capsule while the body had increased greatly in width. This
caused the small head capsule to be pushed forward and gave
the larva a very pointed anterior. This phenomenon was noted
in each instar, but was never noted between 0.13 mm and
0.16 mm. In view of this, the writer determined that the
larval head capsule widths between 0.12 and 0.18 mm represented
only the second instar.

Nine head capsule exuvia, corresponding in width to
those limits set for the third instar, were found on the bodies
of recently molted fourth instar larvae. This verifies that

these two instars are consecutive.

Larval Development
As indicated by the Lawrence seasonal development graph

(Fig 9) the mean larval development is completed in 23 days.

52

Since the larvae have four instars, four stadia each of

about 6 days are possible. This supposition is well supported
if only the initial appearance of an instar is considered
(Table 11). At least 6 days elapsed between the appearance

of the first-and second-, and second- and third-instar. The
third and fourth instars appeared simultaneously on July 2.
Eighteen days had elapsed since the first-instar, hence, the
fourth instar fits well. Some third-instar larvae should have
been.present on June 27 since more than 12 days had elapsed
since the initial appearance of the first-instar.

If the data for each instar are subjected to an
arcsine transformation and graphed, the results are as depicted
in Figure 1N. The first stadium is 11 days in length, the
second, 2.5, the third, 5.5 and the fourth, 7 days. While the
last two stadia concur closely with the field observations, the
first two do not. If the second stadium was as short as
indicated, then the leaves examined in the laboratory should
have contained second-instar larvae for a shorter time than
shown in Table 11. Further study is needed to determine the

stadia length accurately.

Larval Parasitism
An incidence of larval parasitism occurred at Lawrence
on August 10, 1966 when two small black pupae were found in
two separate leaf mines occupied by desiccated.N} slingerlandella
larvae. The pupae were identified as members of the super-

family Chalcidoidea.

 

53

 

 

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Approximately 50 expired larvae collected from
Lawrence and Shelby were dissected from leaves and.placed in
humid containers at 80 F in an unsuccessful attempt to rear
parasites. The dead larvae from.Lawrence often exhibited a
characteristic reddish-purple color on some parts of their
body; many also contained fungal mycelium, Which may be an

indication that microorganisms attacked the larval forms.

Egg and Larval Survival

To obtain an estimate of egg and larval survival in
Lawrence, mined leaves were gathered in mid-July of 1967 at
random to a height of 7 ft. Of 210 eggs examined, 180
hatched; of these, 116 larvae expired, N7 pupated, and 17
were still mining in the leaves. This indicates an egg
viability of 85.7%. Some of the 17 live larvae would
undoubtedly perish before pupation; therefore, the larval

survival is approximately 30%.

Description of the Mine
Each instar produced a characteristic mine. The first

instar's mine was very fine and winding; the second, less
winding and slightly larger in the diameter. The third
instar's mine was relatively straight, again of a larger
diameter. The blotch part of the mine (Figs 15 and 16),
formed by the last instar, was usually rather oblong'with

the frass laid down in an irregular zig-zag pattern. The

actual shape of the blotch depended on the relative

 

57

 

Fig 15.-Typical mines of Nepticula slingerlandella
on tart cherry.

 

 

Fig l6.-Sequence of host plant leaf damage caused by
Nepticula slingerlandella. An unmined leaf in the upper
right, mines and some chlorosis in lower right, more
severe yellowing with resulting defoliation at left.

 

58

interveinal space between the primary leaf veins. The last
instar could not mine through the larger veins and was,
therefore, limited in the leaf area that it could mine. If
the larva happened to locate in an area where the veins were
close together, as was usually the case on tart cherry, the
blotch was rather long and narrow. If the interveinal space
was wide, which was more usual on plum, then the blotch was
round or oval with the frass laid down in a central heap at the
base. The larva in the blotch was visible through the upper
cuticle of the leaf. Its head moved slowly from side to side,
while the posterior portion of the abdomen remained relatively

stationary.

ngal Development
The contents of many pupal cases removed from orchard
litter in the fall of 1966 and spring of 1967 were examined for
development, viability, and parasitism. Development of larvae
that had been allowed to pupate in sterile greenhouse soil in
humid, clear plastic breeding boxes also was observed. 8
After it drops to the orchard floor, a larva immediately
spins a small, light colored cocoon in the orchard litter.
The larva becomes more compact and wing pads begin to form as
anterior lateral projections which 1engthen.posterior1y and
curve beneath the abdomen (Fig 17). Legs and antennae form
and are neatly placed between the wing pads. A transverse,

mesially interrupted, row of short spines forms dorsally on

 

59

 

Fig l7.-Sequence of Nepticula slingerlandella pupal
development. Youngest to oldest, left to right.

 

 

'7' o ' . ‘_"* ‘7
‘- .I1_’\:\?..z. "t w

 

 

Fig 18.-Ventra1 view of an overwintering Nepticula
slingerlandella pupa with part of its case removed.

60

the posterior of abdominal segments one through six, accompanied
by dorso-lateral projections of abdominal segments one through
seven. The eyes become black, while the head becomes orange.
The wings and visible venter become a grey-yellowish—red while
the dorsum of the abdomen remains green. The antennae lenghten
while their annulations darken. This transformation to the
overwintering form (Fig 18) is completed.within a period of 6
weeks.

Three weeks prior to adult emergence the overwintering
pupa begins the spring maturation process. The wing pads
darken at the midrpoint while the light fascia become faintly
visible. Simultaneously the legs and antennae become a darker
grey. The wings darken in both directions from the midrpoint
and the fascia become more apparent. The front femors darken,
the wings become a uniform dark grey, while the dorsum of the
thorax takes on a grey coloration. The abdomen becomes
greyish while the antennae and front legs become a dark grey.
The pupa at this stage closely resembles an adult encased in
a skin (Fig 17) and undoubtedly is very close to emergence.

To obtain an estimate of the threshold temperature
necessary for pupal development, infested orchard litter
gathered on May 3, 1967 was placed in three closed, clear
plastic pint containers and was incubated at 60, 70, and 80 F.
Except for May 10, the samples were checked daily for adult

emergence.

61

One adult emerged in both the 70 and 80 F containers
on May 10 or 11 and in the 60 F container on May 15.
The threshold (T) was estimated by the following

formulae:

at 60 F, K = (No. of days) (60 - T)
at 70 F, K = (No. of days) (70 - T)

at 80 F, K

(No. of days) (80 - T)
Where K = degree-day constant.
The number of days to emergence at 70 and.80 F was

between 7 and 8 days. The mean (7.5) was used as the most

reliable estimate. At 60 F emergence took 12 days.

Therefore:
at 60 F, K = (12) (60 - T)
at 70 F, K = (7.5) (70 - T)
at 80 F, K = (7.5) (80 - T)

Since all equations equal K, T was found by algebraic
substitution. The 70 and 80 F equations were each in turn

compared to the 60 F equation.

At 70 F
12 T - 7.5 T = 720 - 525
N.5 T = 195
T = N3.3 F

62

At 80 F
12 T - 7.5 T = 720 - 600
N.5 T = 120
T = 26.6 F

The actual threshold undoubtedly lies between these
limits, the mean, 3N.9 F (approximately 35 F) is the best
estimate of the pupal developmental threshold as shown by

these data.

Pupal Survival

During the 3 weeks before 1967 emergence occurred at
Lawrence, 335 pupal cases were removed from infested litter; of
these, 193 contained dead pupae while 127 contained pupal skins
indicating that adult emergence had taken place previously.
Fifteen cases contained viable pupae while six, contained small
holes with dead pupae inside (Fig 19), which indicated
parasitism as reported by Crosby (1911). This indicates a
pupal survival of about N0% with less than 2% parasitism.

Six out of the seven live pupae collected in the litter
at Lawrence on May 13, 1967 had begun spring maturation.
This indicated that most pupae emerged as adults the year
following their entrance into the soil. It is possible that a
small proportion emerge every other year. ‘While 7 pupae is a
small number on which to base an assumption, these did
represent the number of live pupae found in 1N2 pupal cases

collected throughout the Lawrence block.

63

 

 

ff—a. _ a

Fig 19.- Nepticula slingerlandella pupal case showing
the emergence hole of a parasite.

6N

Pupal Diapause

 

To determine if the pupae require a diapause, larvae
from infested leaves were allowed to pupate in three closed
clear plastic boxes held at room temperature. The boxes, which
measured 8 x 12 inches were partially filled with moist, sterile
greenhouse soil. At the end of 3 months no emergence had taken
place and no pupae had matured.past the overwintering stage.

Infested litter collected at Lawrence in November was
placed in closed onefipint, plastic containers and refrigerated
at either 25 or NO F. One container was removed from each
temperature cabinet for each of N weeks and incubated at room
temperature. After 6 weeks at room temperature, adults emerged
in the containers held at 25 F for 3 and.N weeks. NOne emerged
in the other cantainers. Thus a diapause appears necessary for

this insect to complete its development.

Alternate Host Plant Studies
Sleeve cages were employed to test the response of
N} slingerlandella to other possible host plants. Two sleeves

were placed on.pin.cherry, Prunqupennsylvanica L., two on wild

 

black cherry, Prunus serotina L., and three on peach, Eggpgs
persica L. In addition, two seedling Stanley prune trees,
Prunus domestica L., were placed in the Lawrence block.
Additional field observations were made on wild black cherry
trees located near Lawrence and Oshtemo, and on pin cherry

trees in Lawrence and Bangor (Van Buren County).

65

There were no indications that N} slingerlandella
attacked wild black cherry. An examination of leaves from the
sleeves indicated that no oviposition had taken place.

Three second instar larvae were observed in two peach
leaves removed from one sleeve. Other peach leaves indicated
that limited oviposition had taken place. Evidently the larvae
develop much more slowly in peach, since larvae in other hosts
had pupated some time earlier.

The leaves of pin cherry were heavily attacked by

N} slingerlandella and appeared to be as favorable a host as

 

tart cherry. A suspected.pin cherry infestation in Bangor where
trees were heavily mined in 1966, was confirmed with the capture

of one N. slingerlandella adult on a black sticky board.

 

The Stanley prune trees were very heavily attacked,
with 88.5% of the leaves showing evidence of mining. Prune

may be the favorite host of N. slingerlandella.

Meteorological Studies

The U.S. weather Bureau.pub1ishes air temperature and
growing degree day information useful in predicting certain
natural phenomenon. The following experiments and observations
were made to determine if these data could be used to predict
‘N. slingerlandella adult emergence.

An experiment was initiated to ascertain the relationship
between the temperature in the air and that which occurred
simultaneously in the orchard litter, the resting place of the

pupae. A thermistor was placed l/N inch below the litter

66

surface N ft northeast of a tart cherry tree located at the
Oshtemo orchard. The thermistor was connected by a 50-ft lead
to an electronic unit which recorded the litter temperature
continuously from.May 3 through May 29, 1967. For an identical
period, air temperature was recorded by a hygro-thermograph
located at ground level 1 ft north of the thermistor.

A mean daily temperature was computed by averaging the
temperatures recorded at 2 hr intervals by each instrument.

The threshold temperature of the pupae, 35 F, was then subtracted
and the remainder recorded as degree-days. The weekly and total
summation is given in Table 12.

The litter registered about 150 more growing degree-days
than did the air for identical periods and location. It appears,
from this limited data, that air and litter temperature may not
be sufficiently related to allow an accurate prediction of
‘N. slingerlandella adult emergence from air temperature data.

To test this conclusion, air temperature data from Paw
Paw, 10 mi east of Lawrence, and from Mears, 3 mi northeast of
Shelby, was reviewed. ‘When the pupal developmental threshold
temperature (35 F) was used as the base, 680 spring growing
degree-days were required for adult emergence at Lawrence in
1966 and 652 were required in 1967 indicating a close annual
relationship. At Shelby comparable data were 1202 growing
degree days in 1966 and 811, in 1967, demonstrating a poor

annual relationship.

67

Table 12.-Air and orchard litter temperature summation
from continuous temperature measurements. Oshtemo,

Michigan. 1967.

 

 

 

 

 

Air Temperature Litter Temperature
Dates (inclusive) mean degree-days mean degree-days
35 F 35 F
May 3 - 6 N1 2N N6 NN
7 - 13 N7 82 51 111
1N - 20 52 120 59 166
21 - 27 57 15N 6N 203
28 - 29 58.5 N7 61 52

Total 50 N27 56 576

 

68

Growing degree-days recorded after N} slipgerlandella

 

pupation in 1966 were added to the growing degree-days recorded
until adult emergence in 1967. These totaled 3N66 degree-days

at Lawrence and 2918, at Shelby. It appears that air temperature
summation will not consistently predict N} slingerlandella

emergence.

Control Studies

 

In 196N, chemical control studies were conducted at the
Lawrence orchard. A completely randomized block of 76 trees
was used as the experimental design. Each chemical was
replicated four times. Nine different insecticides, applied
as single and double sprays, were tested for efficacy against
adult moths. The chemicals were applied as a dilute spray to
the point of runoff (about 10 gal per tree) with a hand held
spray gun which operated at N00 psi.

On May 18, 196N the chemicals were applied to all 72
test trees; four check trees were not sprayed; on June 1, 36
test trees received a second application. Each treatment was
evaluated on July 9 for the presence or absence of mines
through a check of 800 leaves (200 per tree) collected at
random to a height of 7 ft (Table 13).

Azodrin (dimethyl phosphate, ester with.g;§_3—hydroxy-
Nemethylocrotonamide) gave outstanding results. Azinphosmethyl,
RP 1197N (§f((6-chloro-2-oxo-3-benzoxazolinyl)methyl).QLQ-diethyl
phosphorodithioate) and GS 13005 (§7((2-methoxy—5-oxo-Zl2-l,3,N,

thiadiazolin—N-yl)methyl)‘ngedimethyl phosphorodithioate) also

69

Table 13.-The effect of various toxicants on Nepticula

slingerlandella adults. Lawrence, Michigan. 196N.

 

 

pounds active

 

 

Toxicant material per 100 % leaves infested

gal of water Block 1 Block 2
Azodrin 3.2 EC 0.5 1 0
GS 13005 No WP 0.5 8 3
RP1197N N E0 0.5 12 N
Azinphosmethyl 25 'WP 0.25 3 6
GS 12968 NO 'WP 0.5 31 8
Nbsural 50 'WP 1.0 32 10
Diazinon 50 'WP 1.0 N7 11
Phosphamidon N EC 1.0 53 29
Check (average) - 71 71

 

Block 1 treatments applied on May 18, l96N. Block 2 treatments
applied on May 18 and June 1, 196N.

70

gave good control. Diazinon, GS 12968 (0,0-dimethyl-S1175-ethoxy-
1,3,N-thiadiazol-2(3H)-onyl-(3)-methyl_7dithiophosphate) and
Mesurol (N-(methylthio)3,5-xylyl methylcarbamate) gave adequate
commercial control in the block that received two applications

of material. Phosphamidon and carbaryl were not effective in
either block.

In 1966, eight chemicals were applied at Lawrence as a
single application to test their efficacy against first-instar
larvae. A randomized block design which utilized 27 trees
divided into three blocks of nine trees each was used as the
experimental design.‘ Each chemical was replicated three times.
On June 25, each chemical was applied, using the 196N method,
to a separate tree selected at random in each block.

On July 15, each treatment was evaluated for the
presence or absence of mines by checking 600 leaves (200 per
tree) selected at random to a height of 7 ft (Table 1N).

All insecticides tested gave good control. There were
no significant differences (at 5% level) between chemicals,
but all were significantly better than the check.

The formulas of those experimental chemicals that have
not been.previously given are: GO 6506 (dimethyl pf(methylthio)
phenyl phosphate), NIA 102N2 (2,3-dihydro-2,2-dimethyl-7-
benzofuranyl methylcarbamate), Imidan (9,9-dimethyl _S_-
phthalimidomethyl phosphorodithioate) and SD 8NN7 (2-chloro-l-

(2,N,5-trichlorophenyl) vinyl dimethyl phosphate).

71

Table lN.-The effect of various toxicants on Nepticula

slingerlandella eggs and larvae. Lawrence, Michigan. 1966.

 

 

 

pounds active
Toxicant material per 100 % leaves infesteda
gals of water

 

GS 13005 No WP 0.25 3.5
GC 6506 25 WP 0.25 N.0
RP1197N 30 WP 0.N0 N.8
NIA102N2 50 WP 0.50 7.1
Azinphosmethyl 25 WP 0.25 9.9
Azodrin 5 EC 0.17 9.9
Imidan 50 WP 0.50 1N.5
SD 8NN7 75 WP 1.50 15.8
Check - 66.0

 

aNo significant (5%) difference between chemicals; all were
significantly better than the check at the 5% level.

72

In 1967, four chemicals were tested at Lawrence as
ovicides, larvicides, or combination ovicide-larvicide
treatments. A randomized block design, which utilized 39 trees
divided into three blocks of 13 trees each, was used. Each
treatment comprised a chemical, replicated three times, applied
either as an ovicide (A), larvicide (B) or combination ovicide-
larvicide (0). On June 8, A and 0 sprays were applied using
the 196N method. On June 19, B and C sprays were applied.

Each treatment was evaluated on July 12 for the
presence or absence of mines by checking 600 leaves (200 per
tree) randomly collected to a height of 7 ft (Table 15). In
the larvicide treatments, only the blotch mines were counted.
Many of the larvae were in their secondror third-instar when
the sprays were applied and small thread-like mines were often
visible.

The ovicide-larvicide sprays gave the most consistent
excellent results. 'With the exception of NIA 102N2, all
insecticides performed well as ovicides; all, performed well
as larvicides. All treatments were significantly better than
the check. NIA 102N2 was significantly less effective as an
ovicide.

Nepticula slingerlandella may be effectively controlled
in the egg, larva and adult stage with chemicals. Two sprays,
spaced lO-lN days apart gave the most consistent control.

A petal-fall spray followed by a first-cover spray against the

adult is preferred. Second— and third—cover sprays against the

73

Table 15.—The effect of several insecticides on Nepticula

slingerlandella eggs and larvae. Lawrence, Michigan. 1967.

 

 

pounds active

 

 

Toxicant material per 100 %41eaves infesteda
gals of water A B C

Azodrin 3.2 E 0.50 O 1.2 0.16
0513005 N0 E 0.N5 3.8 1.7 0
Azinphosmethyl 25 WP 0.25 1.3 5.3 0

NIA 102N2 50 'WP 0.38 16.0 3.2 1.5

 

8The check trees had a mean infestation of 80.5%. A-ovicide,
applied June 8, B-larvicide, applied June 19, C-ovicide-
larvicide, applied June 8 and June 19. All treatments were
significantly (5% level) better than the check. NIA 102N2
was significantly less effective as an ovicide.

7N

eggs and larvae also are effective, but some early mining and
slight defoliation may occur.

Several organo—phosphorous, chlorinated hydrocarbon and
carbamate insecticides gave effective control, therefore, cross
resistance to insecticides should not be an important control

problem for some time.

SUMMARY

Host plants of Nepticula slingerlandella include tart

 

cherry, sweet cherry, pin cherry and Stanley prune, ngpgg
cerasus L., 2. w L., N. pennsflvanica L. and g. domestica L.
respectively. Limited mining occurred on peach, N} persicae L.,
while wild black cherry, g} serotina Ehrh., was not mined.

Adult emergence occurs once annually during full-bloom
and petal-fall of tart cherry. Male emergence predominates
during the first week. However, the sex ratio is 1:1 when
peak emergence is reached 7 to 1N days later. Adult moths live
an avg of 11 days.

Mating, preceded by swarming of the males, takes place
shortly after daybreak and lasts for 2 to 3 hr. Oviposition
occurs at night and usually begins within 2 days after mating.
Eggs are evenly distributed throughout the tree on the underside
of leaves often near a prominent vein. Mean oviposition
climaxed 6.5 days after mean emergence at Lawrence and 10.5
days after mean emergence at Shelby. Fecundity, established by
branch sleeve cages, averaged 17.9 eggs per female.

The larvae enter the underside of the leaves directly
through the egg chorion. The period from oviposition to hatching
averaged 17 days at Lawrence, 19 days at Shelby and 11 days at
80 F in the laboratory. The larvae mine the leaf palisade

tissue predominantly, and are capable of causing premature

75

76

defoliation. Four larval instars were determined by head
capsule measurements. Each instar produces a characteristic
mine. The first-instar's mine is very narrow and winding;
the second'a,is less winding andSlightly larger in diameter;
the third's, is a relatively straight serpentine mine; and
the fourth's, is a wide oval blotch which usually contains
frass laid down in a zig-zag pattern. The larval stage
averaged 23 days at Lawrence.

Pupation takes place in the orchard litter. In a
matter of hours, a small, tan, oyster-like cocoon is constructed
by the larva. Inside the cocoon the larva assumes pupal
characteristics within a week and continues to mature for 5
weeks thereafter. It overwinters in this stage and the spring
maturation.process begins 3 weeks before adult emergence the
following year.

Signs of very limited larval and pupal parasitism were
'found, but the parasites could not be identified. Attack of the
larvae by microorganisms was suspected.

Chemical control studies indicated that insecticides
applied in the petal-fall and first-cover sprays were effective
in controlling the adult moths. Second- and third—cover sprays
directed against the eggs and larvae were also effective, but

some defoliation did occur.

LITERATURE CITED

Braun, A. F. 1917. Nepticulidae of North America. Trans.
Am. Entomol. Soc. N3 : 155-209.

Crosby, C. R. 1911. The plum leaf miner. Cornell Univ.
Bull. 308:218-228.

Crosby, C. R. 1912. Notes on the life history of Nepticula
slingerlandella Kearfott (Tineidae). Can. Entomol. NN :
25-27.

Esau, Katherine. 1953. Plant Anatomy. John Wiley and Sons,
Inc., New York. 735 p.

Kearfott, W} D. 1908. North American tortricidae and tineina.
J. New York Entomol. Soc. 16 : 187.

LeClerg, E. L., W. H. Leonard and A. G. Clark. 1962. Field
plot technique. Burgess Publishing Company, MHnneapolis,
Minnesota. 373 p.

Lindquist, O. H. 1962. A biological study of a new leaf miner
on birch, ngticula lindguisti Freeman (Lep.-Nepticulidae)
in Ontario. Can. Entomol. 9N : 525-530.

Needham, J. G., S. W. Frost and Beatrice H. Tothill. 1928.

Leaf mining insects. The Williams and Wilkins Company,
Baltimore. 351 p.
Slingerland, M. V. 1909. The plum leaf miner. New York Fruit

Growers Proc. 8 : 122.

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MICHIGAN STATE UNIVERSITY I

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