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311293 00852 476

ABSTRACT

THE EFFECT OF ALAR, ETHREL AND MULCHING ON

THE HARDINESS OF MIDWAY STRAWBERRY gFRAGARIA SPP.) PLANTS

 

by Larry James Bradford

Midway strawberry plants were treated November 1, 1968 with 1,000 and
5, 000 ppm Alar (Succinic acid 2,2-dimethyl hydrazide) and mulched November 25
with straw, clear polyethylene, black polyethylene or clear polyethylene plus straw.
Plant samples dug April, 1969 were tested for percent conductivity to determine
cold injury. No signiﬁcant differences existed. Other plant samples, transplanted
May 15, 1969, exhibited no significant differences in plant survival and runner
plant development.

Midway strawberry plants treated with 1,000 and 10,000 ppm Alar or 1,000
and 10,000 ppm Ethrel (2-chloroethane phosphonic acid) November 1, 1968 were
dug November 4, 11, 22 and 27 for cold storage. The fresh weight increased
throughout November except for 10, 000 ppm Ethrel treatment. Plant samples were
dug April 21, 1969 for percent conductivity and transplanting evaluations. Plants
treated with Alar had lower percent conductivity. All treatments, except 1,000 ppm

Ethrel, had signiﬁcant less plant survival and nmnering following transplanting.

THE EFFECT OF ALAR, ETHREL AND MULCHING
ON THE HARDINESS OF MIDWAY STRAWBERRY

(FRAGARIA SPP.) PLANTS

 

By

Larry James Bradford

A THESIS

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

MASTER OF SCIENCE

Department of Horticulture

1970

éc/M/y”
3-/i'70

DEDICATION

In Memory of My Father

ACKNOWLEDGMENTS

The author expresses his appreciation to Dr. Jerome Hull, Jr.
for his support, encouragement and guidance in performing this research
and preparation of this thesis.

I would also like to express my thanks to the Manistee Benzie Horti-
cultural Society for continued support and Mr. Calvin Lutz, Fruit Haven
Nursery, for his encouragement and use of his facilities for much of the
research.

I am especially indebted to my wife, Harriett and my four sons for

their patience and understanding during the past year.

TABLE OF CONTENTS

LIST OF FIGURES .......
INTRODUCTION... ...... . ....... .......... ........... ..
LITERATURE REVIEW.. .....

Environmental Factors Related to Hardiness. . . ......... . . . .

Temperature....... ......
L1ght......
Plant Age
M01sture

Nutrition-00.000.000.00... ..... O...OOOOOOOOOOOOOOOOOOOOO
Physiological Relationship to Hardiness ......... . . . . . ........
Alteration of Env1romnent

MlllChj-ngOOOOOOOOOOOO...0....OOOOOOOOOOOOOOOOOOOOO0.0..
StorageOOOOOOOOOOO0.0.0....00.00.00...00.00.000.000...

Growth Retardants
Strawberry Crown Injury ..... ..

C ritical T emperamre. ...... O O O C ....... O O O O O O O O O C O O O O O 0
Location Of Injury. 0 O O O O C O O O O O O O O O O O O O O O O O O O O O O O O O O O O O 0
Nature of Freezing Injury.

Measurement of Low Temperature Injury ...... . . . ...... .

iv

Page

10

10
10
l 1
12

Page

MATERIALS AND METHODS 14
Storage Experiment on Fall Harvested Plants 15
Mulching Experiment. ..... 16
Storage Temperature................ ................. l7
ShippingTemperatures... ...... ..... 18
Other Conductivity Experiments l8

RESUL'IS 0......0.0.0......OOOOOOOOOOOOOOOOOOOOOOOOOOOOO0......O 20
Storage Experiment With Fall-Dug Plants 20
DECLJSSION.......0.0.0.0........OOOOOOOO...0.0.00.0.00.0...O... 40

SUMMARY ......OOOOOOOOOOOOOOOO00.0.0.0...OOOOOOOOOOOOOOOOOOOOO 45

BBLIOGRAPHY .....OOOOOOOCOOOOOCOO.............OOOOOOOOOOOOO... 47

Table

II

III

IV

VI

VII

LIST OF TABLES

The Fresh Weight of Midway Strawberry Plants on

Selected November Harvest Dates, 1968. . . . . . . . . . . . . . .

The Fresh Weight of Midway Strawberry Plants on
Selected Harvest Dates as Inﬂuenced by Three
Trimming Treatments Following Harvest. . ...... . . . . . .

Effect of Alar and Ethrel on Fresh Weight of Midway
Strawberry Plants at Selected Harvest Dates.
Chemj-cal Appliw Novemr 1, 1968.00.00.00000000000

The percent Conductivity of Midway Strawberry Crowns
Subjected to Mulching and Alar Treatments in
November 1968 and dug April 21, 1969...............

Survival of Alar and Mulch Treated Midway Strawberry
Plants Following Transplanting. Alar Applied
November 1, 1968. Mulched November 26, 1968,
Harvested April 2, 1969, Transplanted May 15,

1969, Evaluated June 5, 1969.

Survival of Alar and Mulch Treated Midway Strawberry
Plants Following Transplanting. Alar Applied
November 1, 1968, Mulched November 26, 1968,
Harvested April 2, 1969, Transplanted May 15,

1969, Evaluated July 3, 1969........................

The Effect of Alar and Mulching on Number of Initial
Runner Plants Present July 3, 1969. Nursery Plants
Treated with Alar November 1, 1968, Mulched
November 1, 1968, Harvested April 2, 1969,
Transplanted May 15, 1969 .....

vi

Page

21

23

25

28

30

31

32

Table Page

VIII The Effect of Alar and Mulch Treatment on Runnering
of Plants Surviving August 5, 1969. Nursery
Plants Treated with Alar November 1, 1968 and
Mulched November 26, 1968, Harvested April 21,
1969, Transplanted May 15, 1969............ ......... 34

IX The Survival and Runner Plant Development of Midway
Strawberry Plants as lnﬂuenc ed by Fall Applications
of Alar, Ethrel and Winter Protection. Chemicals
Applied November 1, 1968 and Plants Transplanted
May l969................................ ........... 37

vii

LIST OF FIGURES

The fresh and dry weight and the percent dry weight
of Midway strawberry plants. Harvested Novem-
ber1968000000000 ...... 0......OOOOOOOOOOOOOOCOOOOOO.

The fresh weight of Midway strawberry plants as in-
ﬂuenced by three plant trimming treatments prior
to placement in storage..............................

Effect of Alar and Ethrel on fresh weight of Midway straw-
berry plants at selected harvest dates. Chemicals
applied Novemer 1, 1968.00.00.000000000000.0....0..

Effect of Alar and mulching on percent conductivity of
Midway strawberry crowns. Treated November, 1968.
Harvested April, 19690..........OOOOOOOOOOOOOOOOO...

Percent conductivity of Midway strawberry plants treated
with Alar of Ethrel or plant samples suspected of
being cold injured

Strawberry temperature during shipping test from Manistee
to East Lansing and return. 1,000 Midway straw-
berry plants shipped between May 8 and May 21,

1969.00.00...00............OOOOOOOOOO0.0.......0...O

Temperatures during cooling of Midway strawberry
plants placed in cold storage after field digging or
after cleaning and packing...........................

Page

22

24

26

29

36

39

40

INTRODUCTION

The annual value of Michigan's strawberry production for the period 1964
to 1969 averaged slightly less than six million dollars. Cherries and apples were
the only Michigan fruit crops exceeding this value.

Bell, Downes and Fulton (3) reported in 1960 that the variety Robinson
accounted for 50 to 60 percent of Michigan's total production and Premier 30 to
35 percent. The United States Department of Agriculture released the Midway
variety to nurseries producing strawberry plants on December 1, 1959. The
Midway variety, because of its excellent quality and yield, was rapidly adopted
by commercial growers. It was Michigan's major variety by 1965 and now repre-
sents about 75 percent of Michigan's planted acreage.

Commercial growers have experienced problems with Midway plantings that
were not generally encountered serious with Robinson and Premier. The most
prevalent problem has been difficulty securing plant stands following transplanting.
Affected plantings are characterized by plants of low vigor and poor runner plant
set. Incidents of plant mortality have varied from a minimum of 5 percent to as
much as 75 percent in commercial plantings.

Michigan nurseries dig strawberry plants in both the fall and spring. Fall-dug
plants are held in cold storage for spring planting. Spring-dug plants are either
held in storage for a short period of time prior to planting or planted immediately.

Strawberry growers have experienced plant mortality difficulties with nursery plants

harvested at either spring or fall.

Michigan nurserymen do not mulch strawberry plants for winter protection.
They have relied upon natural snowfall to provide winter protection. In some years,
the lack of this protective snow cover has exposed plants to midwinter conditions.

Examination of nursery stock in fields exhibiting considerable plant mortality
suggested cold injury might be associated with the mortality problem. If dormant
plants could be dug in the fall, stored until spring and transplanted to the field,
cold injury to the crowns and roots would not likely occur.

This research was designed to evaluate the possibility of harvesting straw-
berry plants in the fall for winter storage and determine when plants might be
sufficiently dormant for best survival after fall digging.

The effect of mulching and mulching in combination with selected growth

regulating chemicals upon nursery plant survival was also studied.

LITERATURE REVIEW

Strawberries are cultured throughout the northern United States but this
does not necessarily denote hardiness. Snow cover provides winter protection
from low temperatures that normally injure plants.

The nature of cold temperature injury to plants has been extensively studied.
Accordingly, much literature is available on cold injury in relation to plant hardi-
ness.

Conditions leading to the promotion of hardening in plants were among the
earliest research projects (24, 28). Levitt (29) in 1956 reviewed much existing
information and facts regarding cold injury and hardiness. Several other books
and reviews deal with plant hardiness and cold injury of horticultural (21, 22)
and agronomic plants (15) and forest trees (37).

Only reports having special significance or relationship to the research work
in these experiments will be reported.

There was very little research on storage of strawberry plants prior to 1955.
At about that time, research workers in Maryland (47), California (46), and
Virginia (38) found fruit yields of cold stored plants comparable to fresh dug plants.

Subsequent research has been conducted regarding controlled atmosphere storage
(32) in relationship to fungus development and temperature effects on plant crowns.
Chemicals have been demonstrated to increase the resistance of plants to the

environmental stresses of drought, heat and cold (39, 19, 36).

Environmental Factors Related to Hardiness

Temperature

 

Angelo (1), working in Minnesota, performed some of the earliest studies
on the relationship between temperature and hardiness of strawberry plants. Ex-
posing some strawberry plants to 32°F temperature for seven days and another
group to 68°F temperature for seven days, he found a marked increase in the
ability of the plants exposed to 32°F to survive subsequent exposure to 14°F
temperature.

In a subsequent experiment, some plants were exposed to temperatures that
alternated every 12 hours at 68°F and 32°F, others held at a constant 68°F and
others at 32°F for a period of six days. Following these treatments, the plants
were frozen at 25°F. Plants held at 68°F exhibited the most damage. In the
alternating temperature treatment, plants at 68°F prior to freezing showed more
damage than plants at 32°F prior to freezing. The plants held at a constant 32°F
exhibited the least damage.

Steele, Waldo and Brown (42) ﬁnd that plants taken from the ﬁeld on
October 10 and November 1, showed more injury than plants dug on December 5
when exposed to freezing temperatures. Greenhouse plants not exposed to fall
hardening conditions were more severely injured by storing at freezing temperatures
than field plants.

Angelo (l) f01md that strawberry plants dug in November and plans dug in

February, potted and exposed to 32°F temperatures for five days and then subjected

to 23°F temperature for 24 hours, exhibited a marked difference in injury.
Plants dug in February exhibited 20 percent injury while November plants

ranged from 85 to 98 percent injured.

ugh;

Dexter (18) studying the effects of light on wheat and alfalfa hardiness,
observed little or no hardening of wheat in the absence of light. Alfalfa
plants kept in the dark were less hardy than those exposed to light.

Angelo (1) excluded light from strawberry plants for 15 days at 32°F
temperatures and found that plants held at the same temperature and exposed

to light, were more hardy than unexposed plants.

Plant Age

Steele et a1. (42) subjected mother plants, ﬁrst-set daughter plants, and
small late-set daughter plants to 18°F and found that all plants exhibited some
injury but the ﬁrst-set daughter plants exhibited the most rapid recovery.

Boyce (4) fomd no signiﬁcant differences in the amount of injury between
mother, first, second and third daughter plants when exposed to temperatures
of 28°, 24°, 20°, 16° and 12°F. In his experiment, the third daughter plants
were well established prior to handling and all plants received the same har-

dening conditions .

Moisture

Steele et al. (41) and Angelo (1) obtained decreases in hardiness of potted

strawberry plants with increasing moisture regimes. Greatest survival of
plants subjected to freezing temperatures occurred at the lowest water
regime where plants received no water and only sufﬁcient water to prevent

them from wilting two weeks prior to freezing.

Nutrition

Davis and Johnson (14) grew strawberry plants in sand culture and varied
the nutrient solutions, to provide a balanced nutrient supply, or excesses and
shortages of essential nutrients. Plants with a balanced nutrient supply with-
stood winter conditions with least injury. Those plants with a shortage of po-
tassium and magnesium exhibited the most injury.

Angelo (1) rooted ﬁrst runner plants in pots. clipped the runners and

placed the rlmners in sucrose solutions but obtained no increase in hardiness.

Physiological Relationships to Hardiness

Strawberry varieties have been reported to differ in hardiness. Most
experiments involved exposing a number of varieties to different freezing
temperatures and observing the amalmt of injury in terms of plant regrowth.

Steele et al. (42) by exposing seven varieties of strawberries to 10°F
temperature fmmd a range of all alive in the Redheart and Narcissa varieties
to all dead in the Erickson. Brierly et al. (8) exposed eight varieties in
early stages of growth to freezing temperature. Beaven and Dunlay exhibited

severe injury. Premier and Wayzota exhibited the least injury. Boyce (4)

subjected plants of 16 varieties to four different freezing temperatures and
rated them for hardiness on the basis of conductivity tests. Catskill, Vesper
and Vermillion exhibited the least injury and Fletcher, Earlidawn and Blakemore

the most.

Alteration of Environment

The plant's environment can be modiﬁed to provide more favorable con-
ditions for survival. Mulching can provide winter protection for strawberry
plants. The cold storage of fall dug plants also avoids winter injury conditions.

Growth regulating chemicals also promote plant hardiness.

Mulching

Several research workers (1, 2, 45) reported increased strawberry yields
‘\e-w__,/—-—-——‘—""‘*' ‘" “-— a“,
after mulching. Prevention of extremely low soil temperature and killing of

w

 

crowns and ﬂowers in years of open winters have been the primary reasons
for increased yields. Iverson (27) in Minnesota and Boyce (4) in New Jersey
reported the type and condition of mulch is important for effectiveness at times

of low temperatures. Wet, compacted is much less effective than dry,

ﬂuffy mulch. When plants were snow covered throughout the winter, Boyce

 

found no signiﬁcant difference between mulched and non mulched plants. In

the second year of his study, non mulched plants without snow cover for 40

days were severely injured. Norton (36) in Washington found black polyethylene
MN

applied in early December and removed by March 1 effectively protected plants

 

q -.....
¢ _- .
,' \

for extended periods of 00F.
W

Brierly and Landon (6) found that strawberry plants mulched too early
/,_.__--
did not harden to their fullest extent and were more likely to be injured
by low teﬁramres than ”plants mulched later.
-..--_._

They also determined respiration rates under mulch and ice conditions
(5, 7) and found high concentrations of C02 and low concentrations of 02
occurred under certain conditions. They found that strawberry plants withstood
these conditions for several weeks without damage and concluded that plant loss

under mulch resulted from low temperature injury.

Storage

Nursery men dig plants in the fall, pack and store them in cold storage
at 30°F for spring planting to have plants for early shipment and to avoid ad-
verse winter conditions. Researchers in Virginia (38), California (46), and
Maryland (47) reported that plants dug in January, in more temperate climates
and held in cold storage produce excellent ﬁrst year yields when planted in
late summer and early fall. Worthington and Scott (47) found cold storage
of plants in polyethylene lined packing crates superior to storing in moss. Poly-
ethylene liners increased storage life, reduced packing and handling costs,

improved plant quality and better field performance resulted.

Lockhart and Eaves (32) obtained 100 percent survival of plants stored
in controlled atmosphere conditions of 5 percent Oz and 5-10 percent C02
compared to 80 percent survival under conventional storage conditons. Plants
in C.A. storage at 32°F exhibited no plant growth or mold formation, whereas
both were apparent in conventionally stored plants. Ice formed on plants in
polyethylene containers at 28°F but not an the C.A. stored plants at 28°F.
Lockhart (31) also found that delay in cooling plants in storage favored mold

development.

Growth Retardants

 

Growth regulat6rs retard growth and increase the resistance of plants
to the alvironmental stresses of drought, heat and cold (10, 11, 19, 36, 37).

Norton (36) subjected strawberry plants to treatments of Alar, decenyl-
succinic acid and antitranspirants and found Alar to increase cold tolerance by
about 50F.

Bukovac, Larsen and Robb (10) working with grapes found an inverse re-
lationship between the degree of wilting and the concentration of dimethylamino -
succinamic acid (DMAS) used in the treatments.

Plunt, Halevy and Shmueli (39) by treating bean plants with several growth
regulating chemicals signiﬁcantly decreased the transpiration rates, increased
root weight and decreased top weight. They concluded that the chemicals might

increase drought avoidance even if they have no effect on drought tolerance.

10

Although the exact nature of the effects of growth retardants on in-
creased hardiness are not known it is felt that it may be related to delayed
senescence, chlorophyll and protein preservation and reduced respiratory

metabolism (23, 40, 44).

Strawberry Crown Injury

Critical Temperature

 

Steele, Waldo and Brown (42) and Brierly and Landon (9) found that the
killing temperature for well-matured and hardened strawberry plants was
about 10°F.

Boyce (4) found that his plants were killed at 16°F. He observed injury
at higher freezing temperatures which resulted in smaller leaf size, fewer
nmners and fewer ﬂowers. His laboratory tests showed that plants were
injured more severely by rapid freezing or rapid thawing or by repeated
freezing and thawing.

Flore (20) conducted laboratory freezing studies with dormant strawberry
plants and found only 25 percent of the plants frozen at 14°F survived. At

50F, no plants survived.

Location of Injury

 

Angelo ( 1) sectioned cold-injured strawberry plants and found that the
medulla of moderately injured plants was brown only at the base of the crown.

In severely injured plants, nearly the entire medulla was brown and in plants

11

that were killed , the top of the medulla below the apex was also brown
as were the large roots. Steele, Waldo and Brown (42) observed that root
damage was not as important as damage to the crown and the upper plant
parts, since healthy crowns with all roots removed produced new roots under
conditions favorable to growth.

Boyce (4) and Flore (20) found a relationship between the amount of
cold damage occurring in the crown of the strawberry plant as measured by

conductivity tests and plant survival.

Nature of Freezing Injury

The exact nature of injury or killing of tissue by cold is not entirely
understood. It seems, however, to be generally accepted that the injury or
killing of tissue by cold involves the disorganization of the substances essential
for the carrying out of the plant life process (29).

Ice formation within the plants takes two forms, extra cellular and intra-
cellular. Extra cellular ice formation is the most common as the water in
this area is the most pure. As ice crystals form, they withdraw water from
the cells. Injury can result either from physical damage to cells from the
ice crystals or from severe dehydration of cells and the resultant disorganiza-

tion of cell components. This usually occurs during periods of gradually de-

clining temperatures.

12

During rapidly declining temperatures , intracellular ice may form
resulting in injury. This injury is generally thought to result when formation

of ice crystals in the protoplasm cause denaturation of the proteins.

Measurements of Low Temperature Injury

Early methods of determining low temperature injury simply evaluated
plant growth after plants had been exposed to different low temperatures (1,
8, 13, 25).

Other methods to evaluate hardiness and cold injury include the amount
of reduction of triphenyl tetrazolium chloride to determine viability of the
plant (41, 43) and multiple freezing points (26, 35).

Damaged cells are subjected to leaching of various constituents and
measurements of these compmmds have been used as an indication of injury.
Dexter (15) measured total solutes, chlorides and sulfate while Mecklenburg
and Pridham (34) used the succhoroid concentration test to measure reducing
sugars.

Dexter (15) measured. the electrical conductivity of solutes leached from
injured cells as a means to determine the extent of low temperature injury.
Killed or injured cells lose their capacity to regulate the diffusion of intra-
cellular electrolytes, increasing conductivity measurements. He froze alfalfa
tissue, placed it in water, and measured the electrical conductance of the

solution. The higher the conductivity reading of the frozen material, the

13

less apt the plant was to recover. His laboratory technique has been used
by many researchers on many different plant species.

Mecklenburg and Pridham (34) modiﬁed this technique to test viability
of roses. Tissue sections were placed in distilled water equal to three times
the fresh weight of the tissue. After 24 hours at room temperature the
electrolyte concentration was measured using a Wheatstone Bridge. The
tissue was then autoclaved for 45 minutes at 220°F, held at room temperature
for 24 hours and a second reading taken. The ﬁrst value representing loss of
electrolytes due to injury was expressed as a percentage of the second reading.
This percentage was referred to as the percentage conductivity value. Boyce
(4) and Flore (20) used adaptations of this method to determine low tempera-

ture injury to strawberry crowns.

MATERIALS AND METHODS

Field experiments were conducted during October and November, 1968
and March through August, 1969 at the Fruit Haven Nursery, Kaleva, Michigan.
Plants were Midway II, virus-free stock grown for commercial nursery stock.
Soil type was Leelanau Sandy Loam. Nursery stock had been grown from
plants set 20 inches apart in the row with 42 inches between rows and grown
under matted row culture.

Dacthal (dimethyl ester of tetrachloroterephthalic acid) at 8 pounds active
ingredient per acre, complete coverage, was applied one week after trans-
planting for weed control.

The preceeding cropping history included sweetcorn in 1967 with oats as
a winter cover. The oats were fertilized with 300 pounds of 14-14-14 per
acre. The strawberry plants were fertilized with 150 pounds of 18-46-0 per
acre pre-plant on April 13, 60 pounds of 33-0-0 per acre on May 26 applied
through the irrigation system and 100 pounds of 33-0-0 per acre applied as
a side dressing on August 5.

The plants were cultivated as needed to control weeds and turn runners
into the row. Insecticides and supplemental water were applied as needed.
Growth regulators used in this study were Alar (Succinic acid, 2, 2-dimethyl

hydrazide and Ethrel (2 -chloroethane phosphonic acid).

14

15

Storage Experiment on Fall Harvested Plants

On November 1, 1968, ﬁve rows of established Midway II strawberry
plants, each 150 feet in length, in the experimental field received one of the
following treatments: 1) Alar, 1,000 ppm; 2) Alar, 10, 000 ppm; 3) Ethrel,
1,000 ppm; 4) Ethrel, 10,000 ppm; and 5) non-treated. All growth re-
gulator treatments were applied with a three gallon knapsack sprayer to
thoroughly wet all plant foliage.

Plants were dug from each of the 5 treatment rows on November 4,
11, 22 and 27, 1968. On each date of digging, plants from each of the 5
growth regulator treatments were subjected to one of the following leaf trim-
ming regimes: (a) foliage removed to leave 2 to 3 leaves per plant; (b)
all foliage removed; and (c) all foliage removed and leaf sheaves pulled from
crown. An additional sample of non-treated plants were dug to be stored at
40°F for 14 days prior to 30°F storage. Plants were blmdled with 25 per
treatment and 3 replications were made of each treatment. The plants were
packed in polyethylene bags and transported by commercial bus to East Lansing
where they were weighed and placed in storage at 30°F with the exception of
plants receiving pretreatment at 40°F for 14 days. Additional non-treated
plants were included in each shipment for both fresh and dry weight determina-
tions. Plants were weighed January 14 and February 11 to determine changes

in fresh weight during storage.

16

On April 21, 1969, each of the 5 treatment rows were divided into
three units. Plant samples dug from each of these plots were placed in
cold storage at 30°F. Plants taken from each of these samples were sub-
jected to conductivity tests to measure cold injury to the crown tissue. In
addition, samples of 25 plants each were taken from each plot May 15, and
planted in ﬁeld planting to evaluate plant survival and growth. This planting
design was a randomized block consisting of three replications and 5 treat-

ments or 15 plots.

Mulching Experiment

 

Three rows of strawberry plants adjacent to the rows used for the
above plant storage studies were utilized for a mulching study. The mulch
treatments applied on November 26 and 27, 1968 were: (1) no mulch; (2)

l. 5 inches grain straw; (3) clear polyethylene . 04 inch thickness; (4) black
polyethylene . 02 inch thickness and; (5) clear polyethylene covered with straw.
The mulches were superimposed on Alar treatments. Alar was applied on
November 1, 1968 at 0, 1,000 and 5,000 ppm. The combination of Alar and
mulching treatments resulted in 15 treatments and there were 3 replications
resulting in 45 plots each consisting of 10 feet of matted plant row.

Plants were dug from each of these plots on April 21 and 22, 1969,
placed in polyethylene bags and stored in cold storage at 30°F. Subsequently,

samples were selected from each treatment and subjected to an electrical

l7

conductivity test. Six crowns, each weighing 8 to 10 grams, were selected
from each of the 45 plot samples and stripped of all foliage, roots and leaf
scales leaving only crown tissue. These crowns were rinsed in tap water
and cut into halves. They were placed in Erlenmeyer ﬂasks, weighed and

an amOLmt of de-ionized water equal to three times the fresh weight of crown
tissue was added. The ﬂasks were stoppered and held on a laboratory bench
at room temperature for 24 hours. A conductivity reading was then made on
the water solution. The solution was drawn into a micro pipette until the
solution covered two electrodes fastened to a Wheatstone Bridge. Conductivity
readings were made directly from the Bridge.

The ﬂasks were then stoppered with porous ureathane foam and autoclaved
for sixty minutes at 250°F, held an additional 24 hours at room temperature
and a ﬁnal conductivity reading made. Percent conductivity was calculated
by dividing the initial conductivity reading by the ﬁnal conductivity reading
and multiplying by 100.

On May 15, 1969, 25 plants were taken from each of the plots, trans-
planted in an experimental field planting. The experimental design was 15
treatments by 3 replications or 45 plots. Ratings for plant stand and runner

plant development were made during the growing season.

Storage Temperatures

 

During commercial digging of nursery plants in April, 1969, the cooling

18

rate of plants stored in bulk boxes was measured as they moved from the
ﬁeld into storage.

The temperature and cooling rate was determined for bundled plants
removed from the packing house sorting belts , stored in polyethylene lined
pacldng crates and cold storage. Temperatures were measured with thermis-

tors attached to a tele-thermometer.

Shipping Temperatures

 

The temperature of l, 000 spring-dug plants was recorded during transit
by commercial bus from Manistee to East Lansing during two round trips.
A 30-day Ryan Recording thermometer was enclosed with the plants to measure
temperature throughout the experiment. The plants were then transplanted

May 21, to determine survival.

Other Conductivity Experiments

 

The protective snow cover was not always present in areas of some
ﬁelds at Fruit Haven Nursery during the 1968-69 winter season. Plat ts
were obtained from these areas and conductivity of crown tissue determined
as described above. In addition, plant samples were planted in the ﬁeld
experimental planting with the Alar-Ethrel planting using 3 replicates of 25

plants each.

19

An Alpena commercial strawberry grower, planted plants in May,
1969. These were obtained from a commercial nursery and some appeared
to be growing poorly. A plant sample taken from this grower's ﬁeld was
subjected to conductivity test.

In May, 1969, conductivity tests were determined for selected plant
samples from a conmiercial storage. The samples contained plants dug
November 5, which had been held in bulk storage and sorted and packed on
November 11, 28, and December 4, 1968. Additional plants from these

samples were transplanted in a commercial ﬁeld.

RESULTS

Storage Experimalt With Fall-Dug Plants

Midway strawberry plants increased in both fresh and dry weight
throughout the month of November as shown in Table I. Figure 1 illustrates
that while both fresh and dry weight increased during November, the percent
dry weight also increased indicating that there is a conversion of plant material
in the plant with the onset of shorter, cooler days.

An examination of the fresh weights for the leaf trimming treatments
(Table 11) indicates the weight increase of strawberry plants during November
occurred primarily in the crown and roots. There is little difference in ﬁnal
weight between the three treatments (Figure 2). Undoubtedly, the additional
foliage on the plants represent the differences occurring throughout the experi-
ment.

The fresh weights of plants receiving the chemical treatments are shown
in Table 1H. The fresh weights of the plants receiving 1,000 ppm Alar and
10, 000 ppm Ethrel closely paralleled the weight of nontreated plants. Plant
weight from the Alar at 10,000 ppm and Ethrel at 1, 000 ppm were considerably
higher at last harvest. The results are graphically illustrated in Figure 3.
There was considerable variation between treatments November 4, 3 days after
treating, suggesting a difference in plant vigor between plots or variation in
selecting plant samples.

Figure 3 illustrates little change in fresh weight for 10, 000 ppm Ethrel

treatment throughout November. This suggests this treatment interferred with
20

21

TABLE I
The Fresh and Dry Weight of Midway Strawberry Plants on Selected

November Harvest Dates, 1968.

 

 

 

Nov. 4 Nov. 11 Nov. 22 Nov. 27
Fresh weight- gm/plant 9.6 13.3 14.3 16.7
Dry Weight - gm/plant 3.9 5.8 6.6 8.5

Percent Dry Weight 41.6 43.6 46.6 53.6

 

22

 

 

 

151
14 1' r0511 "to
13.
12'
ll.
1
grams 10. 1100
9) 190
d wt. 1
8 ./ ry i 80
,7 .
7 ° 31.0
J . ” ‘ percent
6 / so
0‘7'. 4 dry
,5 / ’percent 0
' o , o- " dry wt. ‘ 3 weight
0/ 4" " ‘I‘ ' ‘
4 - --' H10
3 1,30
2 L 20
l r 1110
Ndv.4' Nov.ll Nov.22 Nov. 27

Figure l. The fresh and dry weight and the percent dry weight of Midway
strawberry plants. Harvested Novedber 1968.

23

TABLE II
The Fresh weight of Midway Strawberry Plants on Selected Harvest Dates

as Influenced by Three Plant Trimming Treatments Following Harvest.

 

 

 

 

Treatment Nov. 4 Nov. 11 Nov. 22 Nov. 27
Grams/Plant

2-3 leave attached 11.6 11.4 19.4 23.8

all foliage removed 9.0 11.4 19.2 20.6

leaves & sheaves
removed 8.1 9.4 17.2 21.2

 

24

  

 

 

24 L 2-3 leaves remaining
23 e
22.
all foliage plus leaf
21 . / shelves removed
0
201- 4"all foliage removed
19 r '
18 r
171
green ,
16 1
15 P
141
13)
12.
11 L I '
_, ’ I 2.3 leafs remaining
101 1’ O - - - all feliage removed
I I .’ 'e'e'eall £011.80 plus
9. I leaf sheaf
./
at” v “‘
Nov. Nov. Nov. Nov.

4 ll 22 27

3

Figure 2. The fresh weight of Midway Strawberry Plan a as influenced by
three plant trimming treatments prior to p acement in storage.

25

TABLE 111
Effect of Alar and Ethrel on Fresh weight of Midway Strawberry Plants

at Selected Harvest Dates. Chemical Applied November 1, 196831,

 

 

 

 

Chemical ppm Nov. 4 Nov. 11 Nov. 22 Nov. 27
Grams/Plant

None 11.6 11.4 19.4 23.8

Alar - 1,000 9.4 15.5 20.8 20.6

Alar - 10,000 14.2 18.4 23.2 27.8

Ethrel - 1,000 12.3 13.5 22.4 25.9

Ethrel - 10,000 18.7 17.1 18.5 20.4

 

-l/Data not subjected to statistical analysis.

26

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27

plant growth although no foliage effects were observed.

The fresh weights were determined on January 14 and February 11
for all treatments while in storage. Their determinations indicated no
change in plant weight from the time plants were placed in storage in
November.

Unfortunately, an expansion valve on the refrigeration Imit, servicing
the storage room in which plants were stored, malfunctioned in April. Be-
fore the difficulty was realized, the storage temperature had reached 70°F
for sufﬁcient length of time to result in loss of the plants.

Conductivity tests conducted on the plants receiving mulching and Alar
treatments indicated no signiﬁcant differences between the treatments. (Table IV).
It is interesting to note the percent conductivity to be so similar for all treat-
ments. This is very apparent from observing Figure 4.

The effect of the combination Alar and mulching treatments on plant
survival following transplanting are shown in Table V and VI. A statistical
analysis of this data revealed no signiﬁcant differences between any treatments.
Unusually heavy rainfall in late J1me resulted in part of the ﬁeld plot ﬂooding
for more than 10 days. This resulted in much plant damage in the second
replication and data presented are for only two replications.

The effects of the treatments on the presence of the ﬁrst runner plant

is shown in Table VII. None of the treatment means differed signiﬁcantly,

28

TABLE IV

The Percent Conductivity of Midway Strawberry Crowns Subjected to

Mulching and Alar Treatments in November 1968 and dug April 21,

1969.

 

 

 

 

 

ALAR ppm
Mulch None 1,000 5,000 mean
Percent Conductivity
None 22.4 22.4 23.1 22.6
Straw 22.6 22.6 25.2 23.5
Clear Plastic 21.4 21.2 22.1 21.6
Black Plastic 23.0 26.7 22.3 24.0
Straw & Clear
Plastic 24.0 25.7 24.0 24.6
Mean 22.7 23.7 23.3 23.3

 

No significant difference at .05 and .01 level.

29

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30

TABLE V
Survival of Alar and Mulch Treated Midway Strawberry Plants Following
.TranSplanting. Alar Applied November 1, 1968, Mulched November 26,
1968, Harvested April 2, 1969, Transplanted.May 15, 1969,

Evaluated June 5, 1969.

 

 

 

 

 

ALAR ppm
Mulch Treatment None 1,000 5,000
Plants/Plotl’
None 25.0 23.5 24.5
Straw 25.0 24.5 24.5
Clear Plastic 25.0 24.0 23.5
Black Plastic 24.0 24.0 24.0
Strawr& Clear Plastic 24.5 21.5 25.0

 

1]

Number of plants surviving - 25 transplanted per plot. Means do

not differ significantly at .01 and .05 level.

31

TABLE VI

Survival of Alar and Mulch Treated Midway Strawberry Plants Following

Transplanting. Alar Applied November 1, 1968, Mulched November 26,

1968, Harvested April 2, 1969, Transplanted May 15, 1969,

Evaluated July 3, 1969.

 

 

 

 

 

ALAR ppm
Mulch Treatment None 1,000 5,000
Plants/P1031,
None 25 21 21
Straw 22 20 20
Clear Plastic 25 20 20
Black Plastic 20 22 22
Straw'& Clear Plastic 22 18 22

 

1]

Number of plants surviving 5.25 tranSplanted per plot. Values do

not differ significantly at .01 and .05 level.

32

TABLE VII

The Effect of Alar and Mulching on Number of Initial Runner Plants

Present July 3, 1969. Nursery Plants Treated with Alar November 1,

1968, Mulched November 1, 1968, Harvested April 2, 1969, Trans-

planted May 15, 1969.

 

 

ALAR ppm

 

Mulch None

1,000

5,000

 

1]

Initial Runner Plants

 

Check 15.0
Straw 4.1
Clear Plastic 5.0
Black Plastic 4.6
StraW*& Clear Plastic 6.0

4.5
1.1
5.5
7.0

5.5

2.5

9.0

6.0

1.0

8.1

 

'l/Number of initial runner plants per plot.

per plot.

25 plants transplanted

Values do not differ significantly at .05 and .01 level.

33

suggesting the treatments did not delay development of the initial runner
plants.

On August 5, 1969, plots were rated for runner development of all
surviving transplants in each plot. There was no signiﬁcant difference be-
tween ratings for each treatment (Table VIII).

Plants, from plots treated with Alar and Ethrel for plant storage
investigations, were dug April 21 and percent conductivity determined.

Plants from a knoll area of the nursery ﬁeld that was not snow covered all
winter (designated as "exposed") and from a ﬁeld near Alpena, Michigan that
lacked vigor two weeks following transplanting were also subjected to con-
ductivity tests. The percent conductivity readings are illustrated in Figure 5.
The conductivity reading was extremely high for plants sampled from the
exposed knoll Alar treated plants had a very low percent conductivity.

Plant samples from the treatments , transplanted May 15 were evaluated
June 5, July 3 and August 5, 1969. Table Df presents these evaluations.
Plants treated with 10, 000 ppm Ethrel or from the exposed knoll were signiﬁ-
cantly poorer on June 5. On July 3, the control plants and those treated with
1,000 ppm Ethrel had significantly higher survival ratings than the other treat-
ments. These two treatments also had a signiﬁcantly greater percent of
plants producing runner plants on July 3. On August 5, the non-treated plants
had a signiﬁcantly greater number of surviving plants forming runners than

the other treatments.

34

TABLE VIII
The Effect of Alar and Mulch Treatment on Runnering of Plants Surviving
August 5, 1969. Nursery Plants Treated with Alar November 1, 1968
and Mulched November 26, 1968, Harvested April 21, 1969, Trans-

planted May 15, 1969.

 

 

 

 

ALAR Dom
Mulch Treatment None 1,000 5,000
Check 4.01, 2.0 3.5
Straw 1.5 3.0 2.5
Clear Plastic 2.5 3.5 3.5
Black Plastic 3.0 3.0 3.5
Straw & Clear Plastic 2.5 3.0 2.5

 

'l/4=100%; 3=75%; 2=50Z and 1=25Z surviving transplants with runner
plants.

Values do not differ significantly at .05 and .01 level.

35

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36

TABLE TX
The Survival and Runner Plant DevelOpment of Midway Strawberry Plants
as Influenced by Fall Applications of Alar Ethrel and Winter Pro-
tection. Chemicals Applied November 1, 1968 and Plants Trans-

planted May 1969.

 

 

Z Plants
Treatment June 5 July 3 Runnering Aug. 5
July 3, 1969

 

 

Check 100a” 100 a 60 a 4 all
Alar 1,000 ppm 90a 52 be 1 b 1 b
Alar 10,000 ppm 943 64 b 1 b 1 b
Ethrel 1,000 ppm 100a 92 a 40 a 2 b
Ethrel 10,000 ppm 72b 40 be 2 b 2 b
EXposed plants 72b 27 c l b 1 b
P = .05 .01 .05 .01

'l/4=IOOZ 3=75Z 2=50Z l=25Z surviving transplants with runner
plants.

-2/Means followed by similar letters within a column do not differ

significantly.

37

The temperatures for l, 000 strawberry plants shipped between
Manistee and East Lansing between May 8 and May 21, 1969 are ﬂlustrated
in Figure 6. During transit to East Lansing, the temperature increased
from 50 to 70°F. During the return trip to Manistee, the temperature
rose to 75°F. After being returned to East Lansing, the plants were held
in cold storage for 4 days at 40°F before being returned to Manistee. The
temperature upon arrival at Manistee was 75°F.

The temperatures during cooling for nursery plants dug May 12, 1969
and placed in cold storage prior to packing are presented in Figure 7.
Plant temperature was 70°F when dug and gradually cooled to 35°F. Plants
packed May 12 and placed in cold storage cooled from 54°F during packing

to 32°F within 24 hours and to 30°F within 2 days.

38

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DISCUSSION

Both fresh and dry weight of strawberry plants increased during
November, 1968. However, there was over a ten percent increase in
the percent dry weight between November 4 and 27. This would suggest
the plants might be building up a reserve of essential materials to impart
hardiness to the plant.

There was very little difference in the total fresh weight between
plants for the trimming treatments on November 17. Since fresh weight
for all three treatments increased about 12 grams or over 50 percent
between November 4 and 27, this would suggest the increase in plant weight
occurred primarily in the crown and roots. Long and Murneek (33) found
that weight increases do occur in the roots as plants are exposed to cooler
fall temperatures. They attributed the increase to accumulated sugars,
starch, hemicellulose and nitrogen. The increase of plant reserves, in this
portion of the plant, may be associated with climatic inﬂuence on plant growth
prior to dormancy.

It was intended to evaluate time of fall digging to determine when
plants could best be harvested for satisfactory storing for survival following
transplanting the following spring. Malfunctioning of the storage equipment
prevented completing the transplanting phase of this study.

Plants treated with 10, 000 ppm Ethrel had little increase in fresh
weight between November 4 and 27 while fresh weights for other treatments

40

41

increased twofold. While plants exhibited no unusual foliage symptoms,
this treatment must have been injurious. The percent conductivity was
less for the Alar treatments suggesting this compound may increase plant
hardiness. The percent conductivity for plants treated with 10, 000 ppm
Ethrel was about 5 percent higher than control plants.

Initial survival following transplanting was similar for Alar and non-
treated plants but by July was inferior for Alar treatments. Plants treated
with Ethrel at l, 000 ppm transplanted as satisfactorily as non-treated plants,
but 10, 000 ppm Ethrel resulted in poor survival following transplanting.
Plants from this treatment had leathery root systems and somewhat smaller
crowns with wrinkled appearance, suggesting plant injury.

Alar treated plants did not form runner plants as early in the season
nor as abundantly as non-treated plants. Plants from a knoll in the commer-
cial nursery that did not have continuous snow cover during the winter were
compared with the treatments. The percent conductivity of the exposed plants
was much higher and survival and runnering of these plants was much less
than control plants.

Conductivity tests conducted on plants from the combination mulch and
Alar plots did not differ between treatments. When plants from these plots

were transplanted, no signiﬁcant differences were observed for plant mortality,

42

time of rtulner plant development, or number of plants that developed
runners. Adequate snowfall was present throughout the winter providing
natural protection to all treatments in the study. This probably explains
the similarity of conductivity readings. The relatively low percent con-
ductivity readings suggests that winter injury to the crowns was not serious
since the average conductivity value of all treatments was below 24 percent.
Flore (20) did not ﬁnd plant mortality to become serious until conductivity
values exceeded 25 percent.

Boyce (4) f01md no signiﬁcant difference in percent conductivity and
plant response in mulched versus non-mulched plants when they were covered
with snow throughout the winter. In the year when snow cover did not persist,
signiﬁcant differences did occur in plant survival. and fnlit yield between
non-mulched and mulched plants. Non-mulched plants had lower survival
ratings.

Nurserymen prefer not to mulch their plantings because of mulching
costs and the problem of removing the mulch prior to digging in the spring.
This study suggests that mulching would be beneficial for Michigan strawberry
nurseries to assure protection from cold injury to their plants.

Commercial nursery plants dug November 5, 1968 were held in bulk
boxes and packed into polyethylene lined packing crates on November 18, 28,

and December 4, and placed in cold storage at 30°F. Samples from these

43

packing dates were transplanted and less than 25 percent survived. Con-
ductivity tests prior to transplanting revealed readings above 25 percent
for all three groups of plants. Either plants were not sufficiently dormant
when dug for long term storage or injury occurred during storage. It is
possible a conductivity reading might result from injury not caused by cold.
The temperature recorded during plant shipment by commercial bus
reached 70°F within 24 hours. After plant temperatures were lowered to
32°F for 4 days in cold storage, they rose above 70°F within one day during
subsequent shipments. These temperatures are detrimental to plant survival
and indicate plant injury can occur to nursery plants during distribution from
the nursery under less than ideal conditions. Plants in the shipping study
began to grow during transit and the appearance and odor was not that of
healthy plants. These plants failed to survive.
These results would indicate that mortality problems in Midway plants
of Michigan strawberry growers are primarily a result of cold injury to
the nursery plants. However, improper shipping and handling practices can

also contribute to these difﬁculties.

SUMMARY

Midway strawberry plants were treated on November 1, 1968 with
1,000 and 5,000 ppm Alar. On November 25, straw mulch, clear polyethylene,
black polyethylene and clear polyethylene plus straw were superimposed on the
Alar treated plants. Plant samples taken from the plots on April 21, 1969
were tested for percent conductivity to determine cold injury. No significant
difference was found. Other plants were transplanted May 15 to determine
survival and ability to form runner plants. Again, no signiﬁcant differences
were found between treatments.

Midway strawberry plants were treated with Alar at 1, 000 and 10, 000
ppm and Ethrel at 1,000 and 10,000 ppm November 1, 1968. Plants were dug
on November 4, ll, 22 and 27. Fresh and dry weight determinations were taken
and placed in cold storage at 30°F. Fresh weight, dry weight and percent dry
weight increased from November 4 to November 27. Plant samples obtained from
these Alar and Ethrel plots on April 21 were placed in cold storage and planted
May 15 to evaluate survival and ability to form runner plants. Conductivity
tests were also conducted on these samples. Signiﬁcant differences occurred
between treatments in survival, formation of runner plants and percent conduc-
tivity.

Plant temperatures were recorded for various phases of a commercial

nursery's plant handling procedures. These temperature effects on plant survival

44

45

and ability to runner were studied.

High temperatures during shipment adversely affected survival.

Plants from a nursery area not covered with snow throughout the
winter season were subjected to conductivity and plant survival tests. Per-
cent conductivity and plant loss was higher than in other treatments covered

with snow.

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