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Fruit Notes

Prepared by: Department of Plant and Soil Sciences

Massachusetts Cooperative Extension, University of Massachusetts, United States

Department of Agriculture and Massachusetts counties cooperating.

Editors: W. R. Autio and W. J. Bramlage

Volume 52,No.l
WINTER ISSUE, 1987

Table of Contents

Apple Rootstock Evaluation in Massachusetts

Pomological Paragraph: Revision of Storage Handbook

Pomological Paragraph: Public Opinion About Alar

Mauget Microinjection of Oxytetracycline for Therapy
and Prevention of Eastern X-Disease of Peaches

Strawberry Arthropod Pests: An Introduction
to Strawberry Insect Pest Management

Pomological Paragraph: Market Basket Survey:
Good News for Retailers and Consumers

Monitoring and Control of Apple Blotch Leafminer: An Update

Pomological Paragraph: State of Maine Suspends Action on

Mandatory Tolerances for Alar*

Reducing Energy Costs in CA Storage

An Economic Analysis of Orchard Rejuvenation in Response to
the Reduction or the Elimination of the Use of Alar®

APPLE ROOTSTOCK EVALUATION IN MASSACHUSETTS: 1986

Wesley R. Autio

Department of Plant and Soil Sciences

University of Massachusetts

With the increasing costs of land, labor, and all inputs of orchard
production, there is a need to intensify management. The use of dwarfing
rootstocks is one way to accomplish this while reducing some costs and
increasing returns. However, rootstocks must be evaluated thoroughly prior to
wide scale planting. In this paper 1 would like to present the results of two
rootstock plantings at the Horticulture Research Center in Belchertown,
Massachusetts.

The University of Massachusetts has been involved with the NC-140
Regional Research Committee for a number of years, and in 1980 and 1984
plantings were established at about 30 locations across the country and Canada.
The 1980 planting consists of Starkspur Supreme Delicious on Ottawa 3, M.7
(EMLA), M.9A (EMLA), M.26 (EMLA), M.27 (EMLA), M.9, MAC 9 (Mark), MAC
24, and OAR 1. The EMLA designation means that the source of the rootstock
was a clone which has had the viruses removed. A similar planting of these
rootstocks with Summerland Red Mcintosh as the scion cultivar was established
in 1985.

The 1984 planting includes Starkspur Supreme Delicious on Bud. 491, Bud. 9,
MAC 1, MAC 39, P.l, P. 22, seedling, CG 10, CG 24, M.4, M.7 (EMLA), M.26
(EMLA), Bud.490, P. 2, P. 16, P. 18, CG, and Ant. 313. Descriptions of the origins
of the rootstocks in both the 1980 and 1984 plantings can be found in Fruit
Notes 51(4):22-24.

1980 Planting

Tables 1, 2, and 3 show the sizes, yields, and amounts of suckering of the
trees in the 1980 planting after seven growing seasons. Based on trunk
diameter and height (Table 1), the largest trees were on MAC 24 roots, and
they were significantly larger than those on M.7 (EMLA). Trees on MAC 9
were similar in size to those on M.26 (EMLA). Trees on M.27 (EMLA) and M.9
were the smallest. Interestingly, those on M.9A (EMLA) were significantly
larger than those on M.9.

The hypothetical number of trees per acre (Table 1) was calculated from
tree spread. It was assumed that spacing between trees should be 40% greater
than the present spread, and the distance between rows should be approximately
8 feet larger than the spacing between trees. These data suggest that the
optimal density of MAC 9 is similar to that of M.26 (EMLA). MAC 24 requires
a very wide spacing, approximately 20 x 28 feet.

Yield for these trees is reported in Table 2 as yield per tree and per acre
(calculated from hypothetical tree density) for 1986 and on a cumulative basis.
Generally, the largest trees were the most productive per tree, but the

potential yield per acre was highest for trees on MAC 9 and M.9A (EMLA). In
1986, on a per acre basis, trees on OAR 1, MAC 24, and M.27 (EMLA) were the
poorest yielders.

Table 1. Tree size and hypothetical density in the 1980 planting as measured
on October 15, 1986

Hypothhtical

Trunk

Tree

number of

trees

diameter

height

spread

per acre (+

approx.

Rootstock

(ir

(ft)

(f1

spacing in

ft.)

Ottawa 3

2.2

8.4

7.4

214 (11 X

19)

M.7 (EMLA)

3.2

11.2

9.0

165 (13 X

21)

M.9A (EMLA)

1.8

7.4

5.4

342 (8 X

16)

M.26 (EMLA)

2.5

9.8

7.4

214 (11 X

19)

M.27 (EMLA)

1.0

5.2

2.8

952 (4 X

12)

M.9

1.3

6.2

3.4

760 (5 X

13)

MAC 9

2.5

7.8

7.6

218 (11 X

19)

MAC 24

5.0

14.4

13.0

83 (20 X

28)

OAR 1

2.6

10.4

5.2

377 (8 X

16)

*Means in a column not followed by the same letter are significantly different.

Table 2. Cumulative and 1986 yields per tree and per acre for the 1980
plant ing.

Rootstock

Yield yield

per tree per tree

(1986) (1983-86)

(bu) (bu)

Potent ia 1

Potential

yield

cumulat ive yield

per acre

(1986)

(1983-86)

(bu)

276 abed

817 ab

335 abc

835 ab

380 ab

1067 a

336 abed

944 ab

257 cd

762 ab

327 bed

1110 a

440 a

1131 a

226 cd

623 ab

181 d

539 b

Ottawa 3
M.7 (EMLA)
M.9A (EMLA)
M.26 (EMLA)
M.27 (EMLA)
M.9
MAC 9
MAC 24
OAR 1

1.29 c*
2.03 b
1.11 c
1.57 be
0.27 d
0.43 d
2.02 b
2.72 a
0.48 d

3.82 cd
5.06 be
3.12 d
4.41 be
0.80 e
1.46 e
5.19 b
7.51 a
1.43 e

*Means in a column not followed by the same letters are significantly different.

The number of suckers per tree and per acre are reported for each
rootstock in Table 3. On a per tree basis MAC 24 resulted in many more
suckers than any other rootstock. When the number of trees per acre were
considered MAC 24 and M.9 produced the most suckers per acre.

Table 3. The number of suckers per tree and potential number per acre for
trees in the 1980 planting.

Rootstock

Cumu la live

Potential

suckers

per tree

per acre

(1980-

86)

(1980-86)

0.8

171 b

4.2

693 b

1.6

547 b

5.0

1070 b

0.2

190 b

7.8

5928 a

1.4

305 b

118.4

9837 a

2.6

980 b

Ottawa 3
M.7 (EMLA)
M.9A (EMLA)
M.26 (EMLA)
M.27 (EMLA)
M.9
MAC 9
MAC 24
OAR 1

"Means in a column not followed by the same letter are significantly different.

In 1986 evaluation of fruit quality and ripening of fruit from these trees
began. Results will be reported in later issues.

1984 Plantin g

The trees in the 1984 planting are not old enough for a full evaluation of
tree characteristics, but tree size after 3 growing seasons and bloom are
reported in Table 4. Treus on Ant. 313, Bud. 491, and seedling roots were the
largest, and those on P. 2, P. 16, and P. 22 were the smallest. The number of
flower clusters were counted in 1986 and the bloom is presented as the number
of blossom clusters per unit of trunk cross-sectional area. Because of the
significantly higher amount of bloom, trees on B.9, MAC 39, P. 22, M.26 (EMLA),
P. 2, P. 16, and C.6 likely would fruit earlier than trees on the other rootstocks.
Further observation of these trees will give us insight into new rootstocks
which may perform well in Massachusetts.

Table 4. Tree size and bloom of trees in the 1984 planting.

Tru

Blossom c

lusters

diame er

Height

Spread

per cm^

' trunk

Rootstock

(in)

(ft)

cross-sectional area

Bud.491

1.59

ab*

7.1

4.4

0.03

Bud. 9

1.23

def

7.1

3.1

bcdef

8.87

MAC 1

1.29

cde

7.3

defg

3.3

abcde

0.45

MAC 39

1.04

6.9

3.1

bcdef

5.01

P.l

1.47

a be

8.1

bcde

3.2

bcdef

3.98

P. 22

0.78

4.7

1.8

8.24

Seedling

1.55

8.1

bcde

4.0

abed

1.24

CG 10

1.49

a be

7.9

cdef g

3.9

abed

0.99

CG 24

1.38

bode

8.2

abed

3.6

abcde

0.65

M.4

1.23

def

7.6

cdef g

3.3

abcde

0.80

EMLA 7

1.32

cde

7.9

cdef g

3.6

abcde

1.06

EMLA 26

1.19

7.1

ef g

2.9

cdef

4.51

Bud.490

1.43

abed

7.8

cdef g

3.4

abcde

0.91

P. 2

1.00

fgh

5.7

2.7

def

4.54

P. 16

0.85

5.9

2.3

8.33

P. 18

1.43

abed

8.2

abed

4.0

abed

0.65

C.6

1.18

6.9

3.3

abcde

6.18

Ant. 313

1.64

8.7

a be

4.8

0.50

'Means in a column not followed by the same letter are significantly different.

Conclusions

MAC 9 (sold as Mark) continues to perform extremely well under our
conditions. Trees are similar in size to M.26. They are more stable than M.26,
not requiring support at this point, and they are veiy productive. The other
rootstock which shows a lot of promise is M.9A (E\LA). The source of this
stock is derived from M.9A (a clone of M.9) after the viruses were removed. It
is considerably more vigorous and much more productive than standard M.9. It
could be particularly useful for plantings on posts. The additional vigor keeps
lateral branches more upright and productive longer.

In coming years we will be able to observe Mark with Mcintosh and
several other cultivars in differeni plantings around Massachusetts. It would be
advisable for growers to begin experimenting with Mark in small plantings but,
it is too early in testing to recommend it for large-scale plantings.

- 5 -

POMOLOGICAL PARAGRAPH

Revision of Storage Handbook

William J. Bramlage

Department of Plant and Soil Sciences

University of Massachusetts

The U.S. Department of Agriculture recently published a revision of its
Agriculture Handbook Number 66, "The Commercial Storage of Fruits,
Vegetables, and Florist and Nursery Stock."

The handbook discusses factors that can significantly affect quality
maintenance during storage, and is a wealth of specific information about the
postharvest needs and problems of many horticultural crops. Anyone working
with storage of horticultural crops should have this publication for quick
reference to needs for storing these crops.

Agriculture Handbook Number 66 can be purchased from the Superintendent
of Documents, Government Printing Office, Washington, D.C. 20402. The stock
number is 001-000-04478-8, and the price is $6.00.

POMOLOGICAL PARAGRAPH

Public Opinion About Alar
International Apple Institute

Are consumers concerned about apples? Not really, according to a
national study conducted by Opinion Research Corporation, a San Francisco
based market research firm. The study, conducted in July 1986, reports that
only an estimated nine percent of the population is even aware of any publicity
or news stories of health concerns about apples.

A surprising number of respondents to the study replied that the news
they heard about apples was good. In addition, many other respondents who
remember recently hearing something about apples in the news could not even
recall whether it was positive or negative.

Consequently, the overwhelming majority of consumers are not concerned
with apples and therefore, we hope retailers are not worried.

* * « * *

- G -

MAUGBT MICROINJECTION OF OXYTETRACYCLINB FOR THERAPY
AND PREVENTION OF EASTERN X-DISEASB OF PEACHES

Terry A. Tattar, Julianno Schi>5ffer,

and Daniel Cooley

Department of Plant Pathology

University of Massachusetts

Introduction

Peach X-disease has been considered one of tiie factors that limits
profitability of commercial peach product ion in the Nortlieast. This mycoplasnfia
disease has been brought into remission by trunk injection of oxytetracycline
antibiotics (2). However, the injection met'nods used were very labor intensive
and difficult for peach growers to use in commercial orchards (1). There also
is some evidence that these methods have led to significant trunk dam.ige over
time (Pierson, personal communication). Mauget (J.J. Mauget Co., 2810 So.
Figu<;roa St., Los Angeles, CA 90065) microinjection has been used widely for
trunk injection of shade trees by arborists to deliver f ert ili/.ers, fungicides,
antibiotics, insecticides, and micrunutrients. Recently, a Mauget capsule //ith
4% oxytetracycline (OTC) became available for experimental use in controlling
myc»)plasma diseases of trees. If a simple system of trunk injtsction like the
Mauget microinjection system could deliver oxytetracycline to peach trees
effectively, control of X-disease in peach orchards by trunk injection could be
performed by peach growers. The objcsct of this study was to determine if
Mauget capsules containing 4% oxytetraoycline could be used to control X-
disease in a commc^rcial peach orciiard.

Materials and Methods

Green Acres Orciiard in Wilbraham, Massachusetts was the test site for
this study. In late summer, 1985 it was noted that a number of trees in the
northeast corner of a 5- to 6-year-old peach block (a late variety mixture)
vvere exhibiting sy.nijto ns (reduced apical and radial growth, greatly reduc^^d
fruit yield, chlorotic and red-spotted foliage, prematire defoliation of inner
leav-is, and prematare bud break) of eastern X-disease. At this time several
trees in this corner of the block had already died and replacement trees had
been planted. A number of other trees had one-t'nird to one-half of their
crowns remov'id by pruning.

Antibiotic therapy was performed in an attemjjt to save the living trees
exhibiting X-disease sy^nptjas, and to protect a number of trees growing
adjacent to the affected ones. The metliod cliosen for therapy was trunk
injection with Mauget capsules, which contain 4 ml of i% oxytetra-cycline
(OTC) antibiotic and are disposable after use. On October 7, 1985 twenty-seven
trees were trunk injected using a dose rate of one capsuln using Thiodiin ^^ for ABLM control tnis decision must be rnade
at tight cluster or earlier. Secondly, after a rail ABLM on the horizontal
surface of the trap lose their distinctive wingscal? pattern, making it difficult
to distinguish ABLM from other captured insects.

To correct both of these problems, we experimented with a new trap
position, tacking the trap vertically to the south side of tree trunks at knee
height. Results from our study of ABLlVI behavior indicated that the motJis
accumulate on the lower portion of the tree trunk during the day in early
spring, probably for warmth.

Our results this past season (Table 1) suggested that traps in this position
captured more ABLM earlier in the spring than did traps in the canopy,
although this difference was not statistically significant. ABLM were also more
easily recognized on the traps in the new position, even after a rain.

^The authors wish to express sincere appreciation to the following growers who
participated in this work: Richard Bargeron, Keith Bohne, Dana Clark, Ed
Roberts, and Mike and Tim Smith. Excellent technical assistance was provided
by Suong Nguyen and James Mussoni.

Table 1. Number of ABLM moths captured on red visual traps in two positions
at tight cluster and early pink, in seven commercial orchards.

Trap position

Mean ABLM captured per trap
Tight cluster Early pink

Horizontal in canopy
Vertical in trunk

l.l a*
3.8 a

9.3 a
18.1 a

*Means within a column not followed by the same letter are significantly
different at the 5% level.

Our results in 1986 suggest that if cumulative captures in this new
position exceed 3-6 ABLM per trap by tight cluster or 18-22 by early pink, an
insecticide treatment for ABLM may be desirable. This is a very rough
approximation, based on results in only 7 blocks. We will continue testing in
1987 to refine these estimates. In the meantime, wc liave continued confidence
in the treatment threshold of 13 ABLM per trap by early pink for traps placed
in the tree canopy.

We also tested a spray tank additive, Nu -Fi lm-17 ' '" (6 oz./lOO gal.), with
a single Thiodan^'^ (1 Ib./lOO gal.) treatment for ABLM at tight cluster.
Growers using Thiodan for ABLM usually have found 2-3 pre-bloom applications
to be necessary for good control. We hoped tliat Nu-Film-17, advertised as a
spreader-sticker which extends the residual activity of insecticides, would hel[o
to reduce the numbc of Thiodan applications needed.

Our results did not bear this out, however (Table 2), Nu-Film-17 appeared
to have no influence on the efficacy of Thiodan. It is noteworthy that both
the single application of Thiodan and the Thiodan + Nu-Film-17 reduced ABLM
mine densities, but not below our threshold of 0.13 first generation mines per
leaf, supporting previous evidence that a single application of Thiodan pre-
bloom usually is not sufficient to control ABLM.

Table 2. Effectiveness of Thiodan^'" + Nu-Film-17'''", Thiodan ilone, and no
treatment against ABLM. Applications were made at tight cluster in
four commercial orchards.

Treatment

1st Generation
mines per leaf

Thiodan

Thiodan + Nu-Film-17

Untreated

0.13 a*
0.14 a
0.26 b

*Means within a colunn not followed by the same letter are significantly
different at the 5% level.

- 14

VVc also tested a new material, Dimilin^'" for control of ABLM, Dimilin is
a chitin syntht sis inhibitor which acts against both ABLM adults and eggs.
Dimilin has lonj; residual activity and is reported to be non-toxic to beneficial
predators, reducing the risk of mite and aphid build-up associated with the use
of synthetic pyrethroids [see Fruit Notes 51(2):6-8]. A single application of
Dimilin (4 oz./lOO gal.) was very effective in controlling ABLM when applied at
tight cluster (Table 3), as was Vydate"*" (1.5 pt./lOO gal.) applied at early pink.
ABLM mine densities in the treated trees remained well below treatment
thresholds through the second generation.

Table 3. Influence of pre-bloom application of Dimilin'"^ and Vydate "^ on
ABLM densities in three commercial orchards.

1st Generation 2nd Generation

Treatment mines per leaf mines per leaf

Dimilin at TC 0.04 a* 0.08 a

Vydate at EPK 0.02 a 0. i? b

Untreated 0.26 b 0.60 c

*Means within a column not followed by the same better are significantly
different at the 5% level.

We also tested Dimilin for control of 2"*^ generation ABLM (Table 4),
applying a single treatment at 2"fl cover in one orchard, ard two treatments (at
2nd oover and 19 days later) in another orchard. Our results showed significant
reductions in ABLM larval densities in treated trees in both orchards.

Table 4. Influence of a single application of Dimilin (Block 1) at 2nd cover
(2C) and two applications of Dimilin (Block 2), one at 2nd cover and the
second 19 days later, on ABLM densities.

2nd Generation
Treatment mines per leaf

Block 1: Dimilin at 2C

Untreated 0.81 b

Block 2: Dimilin at 2C +

19 days later 0.05 a

Untreated 0.60 b

*Means within a column not followed by the same letter are significantly
different at the 5% level.

Our results with Dimilin agree vvith results from other states and Europe.
Hopefully, Dimilin will be available for use in the near future.

- 15 -

In conclusion, the visual monitoring- trap for ABLM has been used
successfully to determine the need for an insecticide application before bloom in
many orchards. A new position for this trap may improve its usefulness by
allowing an earlier treatment decision and reducing confusion in the
identification of the insects captured. Dimilin holds promise as a new selective
treatment option for ABLM without threatening biological control of mites and
aphids.

The ABLM has become an important pest in our region by having
developed resistance to organophosphate (OP) insecticides commonly used in
commercial orchards. Beneficial parasites which control ABLM very effectively
in unsprayed trees are killed by these OP's and other insecticides. Whatever
we can do to reduce insecticide use in our orchards, through the use of IPM
sampling techniques lor example, will help to spare these beneficials and allow
them to assist us in controlling ABLM.

* « * « *

POMOLOGICAL PARAGRAPH

State of Maine Suspends Action
on Mandatory Tolerances for Alar

International Apple Institute

Robert Deis, Director, Maine Bureau of Public Service, in an October 10,
1986, memorandum to food processors said that because "many food processors
have voluntarily decided to discontinue their use of Damino/-ide-treated raw
products and many farmers, part iculirly apple growers, have substantially
reduced their applications of Daminozide--we expect this will lead to a
significant reduction in public exposure--we are therefore suspending
implementation of mandatory state tolerances in hopes that the-y will be
unnecessary. "

The residue guidelines considered in Maine (and the basis for acceptable
voluntary action) are 1 ppm for infant and baby food and 5 ppm for general-
use, heated, processed food packaged before 10-1-86 and non-detectable and 1
ppm, respectively, thereafter.

Rather than setting mandatory tolerances, it was pointed out the state was
taking non-regulatory steps which include a survey of processors to clarify the
extent and nature of their Daminozide policies and to monitor residues of
Daminozide/UDMH in products sold in Maine. The memoriindum to processors
indicated that if product is found to have residues above what the state
considers acceptable levels, voluntary withdrawal of lots will be requested.

Reprinted from Apple News 17(5):l-2.

RBDUCIN*; ENERGY COSTS IN CA STORAGE

J. A. Bartsch

Cornell University

Agricultural Engineer

Dedication

This work is dedicated to Professor Robert M. Smock, who in 1938
published the results of his research on evaporator fan cycling to save energy.
We are grateful for his constant support and encouragement in this project and
in all fruit storage programs. Dr. Smock suffered a fatal heart attack on April
22, 1986 as he walked across the Cornell campus to his office in the Pomology
Department.

Introduct ion

The concept of reducing cold storage energy use through evaporator fan
cycling is not new. In 1938 R. M. Smock (2), a Pomologist at Cornell
University, wrote of his work, "Certainly no differences were indicated in this
study which would justify the extra power cost of continuous blower operation."
Smock's study indicated that fan operating time could be reduced by 45% with
no detrimental effect on fruit quality and condition. Thirty plus years have
elapsed, and now the merits of this original research are being discovered and
applied to modern CA storage in New York.

Storage Technology

Fruit storage technology has changed tremendously since the first cold
storages were built in New York State. The handling, cooling, and storage
milestones are highlighted in Table 1.

Table 1. Commercial loading and cooling rates for apples.

Year

Loading
Period

Cool ing
Time

Room
Atmosphere

Handling
Method

1924
1938
1945
1965
1986

2-3 weeks
2 weeks
1 week
1 week
5 days

1 week

1 week
3-4 days
2-3 days
"overnight"

Air
Air
CA
CA
"Rapid"

Barrels

Bu. Box

20 Bu. Bin

The industry began to use on-farm refrigeration for apples stored in
barrels around 1924. Professor Smock's study involved refrigerated air storage
of apples in bushel boxes in 1938. Around 1945, commercial CA storage was
begun, and by 1965, the importance of faster cooling was recognized and 20-
bushel pallet bins were in widespread use. Currently, commercial operations are
striving for overnight cooling and rapid CA.

17-

The technology change has required increased cooling capacity for pull
down, which Is reflected In larger evaporators and bigger air handling systems.
The very first refrigerated rooms relied upon gravity refrigeration and contained
no supplemental air circulating equipment. By 1938, forced air blower units
delivered 18 air changes per hour and added approximately 198 watts of heat
per 1,000 bushels of stored fruit. Current centrifugal blower units have a 28
air-change -per-hour capacity. Direct throw propeller fans on modern
evaporators deliver 90 air changes per hour. The present hardware associated
with both types of systems adds approximately 375 watts of heat per 1,000
bushels of fruit. The heat added by the fan motors is now 2 to 3 times greater
than the heat of respiration of the fruit (130-180 W/1,000 bushels).

The energy budget for a modern New York State CA storage is shown in
Figure 1. These data are for a 120,000 bushel plant equipped with flooded
ammonia refrigeration. The daily electrical requirements for cortpressors and
evaporator fans are shown along with the total for the refrigeration system.

2500

2000 -

1500

1000

500 -

• 40 Hp Conprcssor

'^''^^l^p^hiA,^^'^

7S Hp Compressor

'"' '^A'^^A^

OCT

NOV

occ

JAN

rcB

APR

MAT

Fig. 1. Daily energy consumptions in a 120,000 bushel CA storage, where fans
were operated continuously.

The "measured total" includes the relatively small amount of electricity used by
water pumps and condenser fans--a quantity which averages approximately 6% of
compressor use. The "metered total" is the daily average electrical use
calculated from monthly power company bills. Hot water heating, office space
heat, and the electricity used by CA burners and scrubbers are included in the
"metered total."

The data in Table 2 indicate that a total energy savings of 40% is possible
if evaporator fans could be turned off half of the time. Total savings approach
60% when fans ire off 16 hours out of 24 hours. Based on early research by
Smock and later reports by Yost (5) half-time reduction in fan operation is
feasible and causes no detrimental effects on stored fruit quality or condition.

Table 2. Daily energy use and potential energy savings through fan cycling
in 120,000 bushel CA storage

Item

Fans
cont inuously

Fans cycle
5 096 on, 5 0%

id
off

25%

ns cycled
on, 75% off

Fans

Coripressor

Condenser

750 kWh

500 kWh

30 kWh

375 WVh

375 kWh

23 kWh

188 kWh

313 kWh

19 kWh

Total use
% Savings

1280 kWh
0%

773 kWh
40%

5 20 kWh

59%

Air Handler

Eff

iciency

During storage trials (1), we investigated the efficiency of high velocity
direct throw air handlers presently used in CA storages. (Efficiency is defined
as the quantity of air returning through pallet runner openings conpared with
the total quantity of air delivered from the evaporator discharge). When
efficiency measurements were made in a 30,000 bushel CA room, 70% of the
discharge air never passed through the stacks; it simply short-circuited over the
top of the bins and back to the evaporator. When air flow was reduced 50% by
turning off half the fans, the return air flow decri;ased only 22%. Since the
measured return flow coming out of the stacks was still uniform over the entire
room, we concluded that half of the evaporator fans could be safely shut down
after field heat was removed and the CA room was sealed.

Control Strategies

The energy crisis of the 1970s prompted eastern growers to begin using
evaporator fan cycling to save energy. The first storage operators to employ
fan cycling simply turned their refrigeration systems off at night and back on
again in the morning during the winter. Research studies (2,4) indicated that
tennperature variations on the order of +^ 1**F from the set point would be
expected when systems were turned off for 12 to 14 hours. We found these
variations to ho, greater than those experienced when refrigeration systems
operated continuously. Since fruit quality and condition after CA storage in the
cycled rooms was equivalent to that in rooms operated continuously, the cycling
practice became widely accepted.

19 -

Our fruit storage industry currently enploys several control strategies for
fan cycling. Manual control is still used by some of the smaller growers. Time
clock control is used, and a few new systems employ programmable load
controllers to sequence fan and refrigeration operations. Presently, however,
the most popular technique is to cycle fans and refrigeration with a solid-state
thermostat. This thermostat, accurate to +^ 0.25OF, can be set to control only
temperature while fans run continuously during loading and pull down. Later
the thermostat is switched to control fans and refrigeration together. Remote
temperature sensors are installed in the CA rooms where the thermostat is used
to control fan cycling.

Initially we were skeptical of using a single thermostat sensor to control
all of the fans in the CA room. Our recommendation still calls for remote
tenperature sensors in all rooms whether fans are cycled or not. We encourage
growers to turn at least some of the fans on for 30 minutes each 12 hours
during very cold weather. We have recorded fan cycles of up to 36 hours off
and 1 hour on when the thermostat alone was used to cycle the fans with the
refrigeration.

After 3 years of experience we are not aware of any fruit condition
problems resulting from the fan cycling methods described above. Some
freezing damage has occurred in open, partially enpty CA rooms, because
insufficient respiration heat was available. Our biggest concern is that
compressor capacity in older plants now far exceeds the load developed in the
CA rooms when fans are cycled. During extended cold periods, machines may
sit idle for 24 hours or more, and provisions must be made to keep the
conpressor room warm. Heat reclaim from these compressors is no longer
possible during the storage season when the fans are cycled.

Temperature, Relative Humidity, and Atmosphere Variations Due to Fan Cycling

We find that the tenperature controller, not the fan cycling practice, is
the cause of major temperature variations in the CA rooms. We have
documented temperature variations in excess of + 20F in rooms with
continuously operated fans controlled by mechanical thermostats. Tenperature
variations in cycled rooms controlled by the solid state thermostats average +
1° or less.

Few data exist for relative humidity variations. Some very limited data
from new storage facilities indicate cycled rooms yield less defrost water than
identical continuously operated rooms. In theory, this should be the case, but
we do not have sufficient data to confirm it for commercial systems.

We are equally short of data on atmosphere concentration variations. In
one study of 1% oxygen storage in a 30,000 bushel CA room, no variation in O2
levels could be detected after the fans were off for 12 hours. This
determination was made by inserting sanpling lines into 6 stack locations during
loading and monitoring the oxygen level with an electronic analyz.er.

SI r

Fig. 2. Monthly energy use in a 300,000 bushel CA storage.

83-Ha
8S-fl6

Fig. 3. Monthly energy use In a 175,000 bushel CA storage.

21 -

Energy Savings

Eastern storage operators are sold on fan cycling to save energy and
dollars. We have documented the monthly savings by two of our commercial
cooperators and present these data in Figures 2 and 3. The "base year" is the
1982-83 storage season, when no fan cycling was used. Conversion to fan
cycling was conpleted in 1984-85; total energy use was reduced nearly 50% in
the process. The need for good storage management with fan cycling is
indicated in Figure 3, where higher than expected use occurred in 1985-86.
This was due to a tenporary change in refrigeration plant management from
October through February in this storage. The new manager was not
"comfortable" with fan cycling practices of the previous year and operated the
evaporator fans for a longer period of time each day during that season.

The fan cycling practice holds great promise for energy cost savings.
Energy rates in the Northeast currently average 11 cents per kWh and electric
costs are a significant part of the total storage budget. Our research has
shown that fan cycling results in a 60% savings in energy in commercial CA
storages. The simple payback on the fan cycling thermostat controller and
remote temperature sensing equipment is currently 4 to 5 months. The value of
energy saved is equivalent to 16 cents per bushel of storage capacity. We
estimate that the potential value of energy savings due to fan cycling is 1
million dollars annually for our CA industry in New York State.

Literature Cited

1. Bartsch, James A. 1982, Consunption and loss of energy in commercial

units. Proceedings of 3^"^ National CA Conference. Timber Press.
Beaverton, Oregon.

2. Blanpied, G. David. 1979. Effect of blower operation upon temperatures in

CA rooms. Unpublished data.

3. Smock, Robert M., and S. R. Shapley. 1938. Blower operation in farm cold

storage. Refrigeration Engineering Vol. 36.

4. Yost, G. E. 1980. Tennperature data from CA rooms operated with
intermittent fan cycles. Unpublished data.

5. Yost, G. E. 1984. Energy saving through the use of fan and refrigeration

cycling in apple cold storage. Transactions of the ASAE:497-501.

* * * « *

AN ECONOMIC ANALYSIS OF ORCHARD REJUVENATION

IN RESPONSE TO THE REDUCTION OR THE

ELIMINATION OP THE USE OF ALAR*^") ^

Martha Kimball and Wesley R. Autio

Department of Plant and Soil Sciences

University of Massachusetts

Since about 1966, Alar''" has been used to extend the harvest season
for Mcintosh apples by controlling preharvest drop and delaying fruit ripening,
enabling growers to efficiently manage harvest labor and cooling capacity.
Without Alar*"', the number of harvest weeks for long-term storage is
decreased, thus increasing the quantity of fruit that must be harvested per day.
To accommodate this higher harvest rate, picking labor and cooling capacity
must be increased, raising production costs. Alternative methods of extending
the harvest season would help alleviate this critical problem.

This study examines the economics of replacing 50 acres of mature,
seedling-rooted trees (that are difficult to pick and lack good color
development) with dwarf and S(imi -dwarf trees that are more efficient to pick,
color well, and allow extension of the Mcintosh harvest. It is assumed that the
grower must replace this block over a 10-year period, rather than all at once,
so that income can continue to be generated each year. The objective of the
study >vas to determine the mix of different Mcintosh strains and rootstocks
that would best use farm resources under Massachusetts production and
marketing conditions during this orchard replacement.

The study was conducted using a multiperiod linear programming model
that was developed specifically for Massachusetts apple growers to aid in long-
range ()lanning of cultivar selection. That model looked at replacing standard
Mcintosh acreages with 7 different cultivars. However, given the commercial
importance of Mcintosh in Massachusetts, we have chose to replant only with
McIntosh--but to use a mix of Mcintosh strains on semi -dwarf ing and dwarfing
rootstocks that will spread the harvest season, best use available resources, and
maximi/.e prof itablility of the orcliarl.

We tried to achieve goals by selei^ting strains and rootstocks with specific
properties. Our goals and choices .vere: I) To produce trees smaller than
standard tliat will produce fruit witii hotter color and ripen earlier (Marshall
Mcintosh on M.7/V); 2) To produce trei^s sn^iller than standard but with fruit
ripening the same time as standard (Rogers Mcintosh on M.7A); 3) To produce
much smaller trees capable of producing fruit for rapid, early harvest (Marshall
Mcintosh on M.26); 4) To produr^e highly colored fruit ripening later than
standard (Marshall McI itosh on 0A.R1). Please note: OARl is an experimental
rootstock that !ias been found to delay ripening of Golden Delicious in Oregon
by about 10 days.

^This study was supported by a grant from the Massachusetts Fruit
Growers' Association

^Hanlon, W. L., C. E. Willis, and R. L. Christensen. 1976. \ framework
for long range apple variety decisions. Mass. Agrio. Exp. Sta. Bull. 621.

- 23

Four management limitations (constraints) were inserted into the model,
namely, cooling capacity, harvest labor, storage capacity, and replanting
acreage. These are described briefly.

\creage: The planting period for the 50-acre rejuvenated orchard was 10
years. Each year 5 acres were removed and replanted. The model also used a
20-year period--10 years beyond the end of replant ing--to evaluate consequences
of strain/rootstock selections up to the time the orchard readies full produc-
tion. For eaiih planting year, the model decided how many acres of each
strain/rootstock combination to plant for maximum prof itabli lity, given the
following set of conditions.

Storage. Most orchards divide the marketing of their crop between the
fresh market, during and immediately following harvest, and long term storage.
However, to simplify the model, we assumed that all fruit produced on the 50
acres was placed in long-term storage.

The storage capacity was set initially at 20,000 bushels. It was increased
to 48,500 bushels in year 20 .vh(>n most ,)lantings had reached lull tnat irity. All
trees less than 4 years old were considered nonbearing mid u-ed none etes only with
Rogers/M. 7A during period 7. In all rnodels, somi- .b^reage of Marshall/OARl
was selected for planting, because it comple nents other strains as an aid in
expanding harvest from 2 vveeks to 4 w;.'cks and provides more efficient use of
labor and cooling capacity.

CONCLUSIONS

It should be remenberid tliat the results of this study were specific to tiie
50-acre rejuvenated orchard described by a given set of conditions. Five acres
of the orchard was replanted yearly for 10 years. The research used the
methodology of multi-period linear programming to determine the number of
acres of 4 different Mcintosh strain-i-ootstock combiiations that should
comprise the replanted acres each year. The objective of planting a mix that
generates the greatest profit over the 20 year period was (^rjustraincd by the
amount of storage, labor, and cooling capacity available during harvest.

Given the limits, Marshall on M.26 composed 66 to 72% of the 50 acres
replanted in each of the alternative >nodels which used varying levels of harvest
labor ind cooling capacity. Marshall/M.26 requires more labor and mat trials at
planting time becau-;c; the trees may requin; staking and may require more

- 28

intensive in.'inageinent during the entire life of the tree. However, several
characteristics contribute to the selection of these trees as the best economic
choice: the trees reach full production earlier, the harvest period is longer,
and fruit can be harvested at a faster rate than those of other strains.

OARl is an experimental rootstock that is being field tested with Mcintosh
in Massachusetts. It was ised in this study to determine its economic potential.
Marshall on OARl was selected by the model when harvest labor and cooling
capacity ^fere most constraining. Due to the experimental nature of this
rootstock Marshall/OAR 1 is not suggested for planting, but these results show
that a combination of strain and rootstock which results in later ripening is
desirable and can have high economic potential. Recent results suggest that
Mark also may delay fruit ripening and may be able to provide benefits similar
to those projected here for OARl. Unfortunately, it also is experimental, but
lias undergone moie thorough testing tlian OARl at this time. Clearly, a
rootstock that delays Mcintosh harvest has great value in a strain-rootstock
mix.

Acres selected for replanting with Rogt^rs on "1.7A increased when harvest
labor and cooling capacity ivere more :ivailable. At the least constraining levels
of resources in the later planting years, Rogers/M.7A substituted for
Marshall/OARl. Thus, availability of labor and of cooling capacity affect
decision-making in this rejuvenation framework.

Lastly, Marsiiall on M.7A was selected minimally. This study did not
recommi'iiil planting MarshaU/M.7A when Marshall/M.26 is an alternative.
However, >vhen M.26 is not an alternativf; because of inadequate soil moisture,
too shallow a soil, or a desire to avoid the more intensive management
required, Marshall/M. 7A would bo the obvious replacement.

Every orchard functions under different conditions; yet, similarities among
orchards in growing and harvesting practices exist. This study examined a
hypothetical orchard. It did not use the costs of any specific orchard.
Alt'iough the results are specific to the rejuvenated 50 acres in the model,
suggestions for replant ing schemes can be rnade. To guarantee that all fruit be
harvested in all cases, harvest labor must be increased to 9 pickers for the 50
acres in year 11 and to 21 pickers by year 20. If this is not done, the entire
crop at full maturity cannot be picked. Also, cooling capacity must be
increased from the original ability to cool 9,000 busliels per 3-day picking
period, to 11,000 bushels per period by year 20.

Table 2 is a suggested 10-year planting mi >c for a rejuventated 50-acre
orchard. It is based upon the research results and should be used as an aid for
grower decisions. Again, because MarsIiaU/OAR I is experimental, it is not
included in the suggest ed plant ing mix. For rejuvenatid acreages of differing
sizes, the percentage values can be applied. For exatrple, in year 3, 60% of a
rejuvenated acreage would be planted with Rogers/M.7A, and 40% planted with
Marshall/M.26.

- 29

Table 2. Suggested planting mix in a 50-acre rejuvenated Mcintosh orchard.

Rogei

rs/M.TA

ir3hall/M.7A

% of

Mars!

mll/M.26

% of

Year

Acres

Planting

Acres

Planting

Acres

Planting

100

2.5

3.5

1.5

LOO

TOTAL

% of total acreage:

2H%

72%

The authors would like to thank the Massachusotts Fruit Growers'
Association for generously supporting this study.

COOPERATIVf EXTENSION SERVICE

U S DEPARTMENT OF AGRICULTURE

UNIVERSITY OF MASSACHUSETTS
AMHERST MASS 01003

OFFICIAL BUSINESS

PENAl TY FOR PRIVATF USE S3()0

BULK RATE

POSTAGE 8. FEES PAID

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PERMIT Nu G:r>8

Fruit Notes

Prepared by: Department of Plant and Soil Sciences

Massachusetts Cooperative Extension, University of Massachusetts, United
States Department of Agriculture and Massachusetts counties cooperating.

Editors: W. R. Autio and W. J. Bramlage

Volume 52, No.2
SPRING ISSUE, 1987

Table of Contents

Soil Applications of Gypsum Can Improve
Apple Fruit Calcium Levels

Pomological Paragraph:
Reducing Fruit Load on Tree Leaders

Can Rootstock Affect Apple Ripening and Quality?

Pomological Paragraph: .
Pruning Well-feathered Trees at Planting

A Report on the 1986 Massachusetts
Apple IPM Program

Pomological Paragraph:
Early, Heavy Cropping of Apples

Results of 1986 Chemical Thinning Trials on Mcintosh

Timing the Tarnished Plant Bug: A Tale of Frustration

SOIL APPLICATIONS OF GYPSDM CAN IMPROVE
APPLE FROIT CALCIOM LEVELS

William J. Bramlage

Department of Plant and Soil Sciences

University of Massachusetts

Calcium (Ca) deficiency in the fruit is a chronic problem in modern apple
production. If this deficiency occurs, it causes poorer keeping quality of the
fruit .

There are 4 possible approaches available for dealing with potential Ca
deficiency in apples. These are cultural practices, soil treatments, foliar
sprays, and postharvest dips or drenches. These approaches were addressed
recently (Proc., Mass. Fruit Growers' Assn. 93: in press).

Of these approaches, soil treatments are generally the least effective due
to the poor ability of apple roots to absorb Ca from the soil solution. We
have tried numerous treatments and have obtained marginal benefits at best.
However, recent results from applications of gypsum (CaS04-2H20) have been
better than any from earlier studies of soil treatments and will be described
here .

We have conducted 2 major trials with gypsum. The first trial was
initiated by Dr. Mack Drake in 1976 in a block of mature, seedling-rooted
Cortland trees. Half of these trees received 80 lbs. of gypsum spread under
the canopy in April and half received no gypsum. Otherwise, the trees were
fertilized and cared for in an identical manner. These applications were
repeated annually through 1986.

During this period leaves and fruit were sampled and analyzed for mineral
concentrations, and fruit were usually stored in both air and controlled
atmosphere (CA) and their quality was assessed after long-term storage.
Results for analyses from 1977 through 1984 are summarized in Table 1. It can
be seen that gypsum treatments increased Ca concentrations in both leaves and
fruit. In addition, they suppressed magnesium (Mg) in both leaves and fruit,
and suppressed potassium (K) in the fruit but not the leaves. Treatment had no
effect on phosphorus (P) levels in either fruit or leaves.

The increased fruit Ca levels improved keeping quality of the apples
(Table 2). Both bitter pit and senescent breakdown were significantly reduced
after both air and CA storage. In the case of bitter pit, the reduced levels
of both Mg and K in the fruit should enhance the benefit from increased Ca,
since it has long been known that high Mg and K worsen the effects of low Ca in
causing bitter pit development. It should be noted that in 1985 there was a
severe bitter pit problem in the fruit on the trees. As we walked through this
block it was very clear which trees had and had not been treated with gypsum,
as the appearance of the fruit was markedly different. In contrast, little
bitter pit occurred in this block in 1986 and no difference was apparent at
harvest time .

The second gypsum experiment was established in 1980 in a block of
Delicious trees planted on MM. 106 rootstock in 1972. This experiment was set

up and conducted by Dr. William J. Lord until his retirement. The trees in
this block received either 0, 50, or 100 lbs. of gypsum spread beneath the

Table 1. Effects of annual gypsum applications of 80 lbs. per tree beneath the
canopy in the spring on fruit and leaf mineral concentrations. Cortland.
1977-1984.

Element

Treatment

Ca (ppm fruit,
% d.w. leaves)

Mg (ppm fruit,
% d.w. leaves)

K (%)

P (ppm fruit,
% d.w. leaves)

Fruit

No gypsum
Gypsum

142
162

303

273

0.63
0.60

420

417

Significance^

•kiiic

***

n.s .

No gypsum
Gypsum

Leaves

0.82

0.26

1.36

0.96

0.23

1.39

1.90
1.86

Significance^

iiik-Jc

***

n.s .

n.s ,

'Significance: *** = odds of 999:1; ** = odds of 99:1; n.s. = not significant

Table 2. Effects of annual gypsum applications, 1977-1984, on fruit quality,
Cort land .

Factor

No gypsum Gypsum Significance^

Firmness ,

lbs

. , harvest

13.4

After

air

stg

9.2

After

11.0

Bitterpit ,

, %,

after air stg

After

Breakdown.

1 "> J

after air stg

After

13.5

9.3

11.1

3
5

12
3

n.s.
n.s ■
n.s .

***

•kick

***
■k-k-k

'Significance: *** = odds of 999:1; n.s. = not significant,

canopy in April. These treatments were repeated each year until 1986, when the
100-lbs. application rate was discontinued. Each year leaves and fruit were
analyzed, and when available (the site is subject to frost), fruit were stored
in 320F air and assessed after long-term storage.

Results are summarized in Table 3. Gypsum increased Ca concentrations in
both leaves and fruit, and decreased Mg concentrations in both leaves and
fruit. It did not affect fruit K and slightly increased leaf K. Gypsum ut 100
lbs. per tree was no better than 50 lbs. per tree in any of these measurements.

Table 3. Effects of annual gypsum applications, 1980-84, on leaf and fruit
mineral concentrations. Delicious.

Gypsum (lbs. /tree) Significance^

Factor 50 100 vs 50 vs

50 + 100 100

Fruit Ca, ppm 145 153 152 *

Mg, ppm 263 258 255 **

K, Z 0.54 0.55 0.55 n.s.

Leaf Ca, % 1.22 1.32 1.36 **

Mg, % 0.36 0.32 0.32 **

K, % 1.36 1.42 1.43 **

zsignif icance: ** = odds of 99:1; * = odds of 19:1; n.s. = not significant.

In this experiment no consistent effect on fruit quality has been
measured. In part this probably is due to the large variability in cropping
among trees, and the consequent variability in fruit quality. For example, in
1986 a severe bitter pit problem existed but it was found only on the large
fruit that were produced on trees that had been damaged by frost. The large
effect of fruit size may have masked any possible benefit from the gypsum
treatments .

These results indicate that soil applications of gypsum beneath the tree
can increase apple Ca concentrations and improve fruit quality after storage.
The effects are modest in size but can produce measurable benefit under
appropriate conditions.

Use of gypsum can, however, create some problems. The obvious one is
suppression of leaf Mg levels. Mg deficiency is common in Massachusetts and
results in loss of vigor and productivity of trees. Our results have shown a
steady decline in leaf Mg in the Cortland block with continuing gypsum
application. Each year leaf Mg was lower than it was the previous year in the
gypsum-treated trees. Clearly, Mg levels would have to be monitored carefully
and corrective measures applied as needed if a gypsum program was adopted.

We do not know what effects long-term use of gypsum would have on soil
properties. These effects must be determined in future assessments.

Likewise, we do not know what application rate is optimum. Since spread
of the trees was different in the Cortland and Delicious blocks, it is more
useful to consider applications in terms of lbs. per square foot. The Cortland
trees were treated with 0.2 lbs. per sq. ft. annually, and the Delicious trees
with 0.3 and 0.6 lbs. per sq. ft. Since the higher rate on Delicious was no
different from the lower rate, it appears that something less than 0.3 lbs. per
sq. ft. may be optimum. However, a comprehensive experiment needs to be
conducted to determine effective rates.

Gypsum treatments are both laborious and expensive when applied as we did.
The material was evenly spread under the trees, a slow unpleasant task. Our
price for gypsum was approximately $0.08 per pound, and therefore the treatment
cost between $3 and $5 per tree per year using the rates reported here.
However, we do not know if gypsum needs to be applied annually. In 1986 the
100 lbs. per tree treatment under Delicious was discontinued, but fruit mineral
analyses showed that Ca level remained equal to that of fruit no longer
receiving gypsum.

At this time, 1 view soil gypsum treatment as an effective way to raise
fruit Ca levels when it is applied as we have. Perhaps the best way to use
gypsum is in an orchard or a block that is known to consistently produce low-
Ca apples. We have another block of Cortland trees that is in very fertile
soil and which produces excessive vigor and large fruit, and these fruit are
always badly affected with bitter pit and breakdown. In 1986 we established an
experiment in this block to see if we can improve fruit quality through gypsum
treatments. Our data show that treatments did not influence mineral
concentrations in this first year. Fruit were not analyzed the first year in
either of the earlier experiments, so this is the first time in which we can
determine the rate at which fruit mineral levels change over time. Based on
the earlier studies, we should see improvements next year.

1 have tried to emphasize that use of gypsum is still very experimental.
It will take a number of years before we can make recommendations with
confidence. However, it is obvious from the results shown here that soil
gypsum treatments can improve fruit Ca levels and quality under some
conditions. It is therefore a new weapon in the modern apple grower's arsenal
of techniques for coping with the ongoing threat of Ca deficiency in fruit.

POMOLOGICAL PARAGRAPH

Reducing Fruit Load on Tree Leaders

Growers should avoid allowing too many fruit to develop on the leader of
young trees. It may be advantageous to remove fruit from the entire tree until
the fourth year. Then for the succeeding years, depending upon tree size, the
removal of fruit from the leader should be continued.

CAN ROOTSTOCK AFFECT APPLE RIPENING AND QDALITY?^

Wesley R. Autio

Department of Plant and Soil Sciences

University of Massachusetts

Interest in the effects of rootstocks on fruit ripening and quality began
a number of years ago. In 1930 Wallace (7) published data suggesting that
apples from trees on M.9 rootstocks had higher soluble solids (sugar) levels
and did not store as well as fruit from trees on other rootstocks. However, if
fruit from trees on M.9 were harvested earlier than others, then similar
storability was obtained, suggesting that M.9 encouraged earlier ripening. In
1944 Hewetson (4) published similar results using Mcintosh trees with various
interstocks. Fruit from trees with an M.9 interstock matured and colored
earlier. Perry and Dilley (6) confirmed these results using the ethylene
climacteric as an index of ripening. In their study Empire apples on MM. Ill
with an M.9 interstock entered the climacteric significantly sooner than those
on MM. Ill alone.

Lord et al. (5) used the ethylene climacteric and soluble solids as the
primary indices of Empire apple ripening and compared various interstock-
rootstock combinations with M.26, M.9, and M.27. They found few consistent
differences with respect to the percentage of fruit in the ethylene climacteric
5 days after harvest. However, consistent differences existed in soluble
solids content. Fruit from trees on M.27 had significantly higher soluble
solids than fruit from trees on M.26, with fruit from trees on M.9 intermediate
between the two. These results suggested that M.27 encouraged earlier ripening
than M.26, and possibly M.9.

Fallahi et al. (2, 3) compared the ripening and quality of fruit from
Golden Delicious trees on seedling roots, M.l, M.7, M.26, MM. 106, and OAR 1.
Using ethylene measurements they found that fruit from trees on M.26 appeared
to ripen earliest, and those from trees on OAR 1 ripened substantially later
than those from all other trees. However, OAR ] also had the highest percent
soluble solids, which is difficult to explain.

It is difficult, from the small number of studies, the small range of
rootstocks used in each study, and the somewhat inconsistent results to compose
a clear picture of the effects of rootstock on apple ripening and quality. The
objective of this study was to use a range of rootstocks, from the very
dwarfing M.27 to the very vigorous MAC 24, to assess rootstock effects on
ripening, size, and quality.

Materials and Methods

Starkspur Supreme Delicious trees on 9 rootstocks (Ott.3, M.7 EMLA, M.9A
EMLA, M.26 EMLA, M.27 EMLA, M.9, MAC 9 (Mark), MAC 24, and OAR 1) were planted
in a randomized complete block design with 10 replications at the University of

^This work was supported in part by a grant from the International Dwarf
Fruit Tree Association.

Massachusetts Horticultural Research Center in Belchertown, MA. To assess the
effects of rootstock on fruit ripening, quality, and size, 7 of the 10
replications were used, 5 planted in 1980 and 2 planted in 1981.

Starting on September 15, 1986, and continuing at 5 day intervals until
October 5, four fruit from each tree were harvested for the measurement of
internal ethylene levels. One-ml gas samples were taken from the core of each
apple to determine the ethylene concentration.

On September 29, 1986 ten fruit were harvested from each tree for the
assessment of fruit weight, length/diameter (L/D) ratio, flesh firmness,
percent soluble solids, and watercore incidence. Firmness was measured with an
Effegi Penetrometer with a 1 cm head. The percent soluble solids was assessed
with a hand ref ractometer , and watercore was characterized by visual assessment
using the method of Bramlage and Lord (1).

Results and Discussion

Table 1 reports the fruit weight, firmness, L/D ratio, percent soluble
solids, and watercore incidence. To accurately assess the effects of rootstock
on fruit size it is necessary to account for crop load. Table 1 also includes
an estimate of crop load in terms of weight of fruit per unit of trunk cross-
sectional area. Additional statistical analyses were performed on these data
to remove the effect of crop load from that of rootstock, and the differences
shown in Table 1 are true estimates of the effects of rootstock on size. Trees
on M.9 produced the largest fruit and those on M.27 EMLA and OAR 1 produced the

Table 1. Fruit parameters and crop load for Starkspur Supreme Delicious trees
on various rootstocks.

Fruit

Flesh

Soluble

weight

firmness

L/D

solids

Watercore

Crop ]

Load

Rootstock

(g)

(kg)

ratio

(%)

index^

(kg/cm2

TCAY)

Ott.3

184

8.39

0.97 ab

11.6 abc

2.0 ab

0.98

M,7 EMLA

196

8.57

0.99 a

11.1 be

1.8 ab

0.72

M.9 A EMLA

192

8.34

0.97 ab

11.4 abc

2.0 ab

1.33

M.26 EMLA

175

8.57

0.96 be

11.3 abc

1.8 ab

0.92

M.27 EMLA

157

8.89

0.94 c

12.0 a

2.4 a

0.91

M.9

200

8.39

0.95 be

11.8 ab

2.3 a

0.95

MAC 9

177

8.34

0.95 be

10.9 e

1.4 b

1.25

MAC 24

193

8.48

0.97 ab

11.1 be

2.4 a

0.42

OAR 1

153

8.98

0.97 ab

11.4 abc

2.2 a

0.27

^Watercore index: 1 = not present; 5 = most severe.

yTCA = trunk cross-sectional area.

^Means in a column not followed by the same letter are significantly different,

smallest. Note that trees on M.27 EMLA and M,9 had similar crop loads and
trees on OAK 1 had a very light crop, suggesting a substantial effect of
rootstock on fruit size. •

Few differences were seen in fruit firmness (Table 1) and those that were
present can be attributed to size, the smaller fruit being firmer. The L/D
ratio (Table 1) was highest for fruit from trees on M.7 EMLA and smallest for
fruit from trees on M.27 EMLA. The differences were statistically significant
and may be of commercial importance.

The percent soluble solids (Table 1) was highest for fruit from trees on
M.27 EMLA, whereas it was the lowest in fruit from trees on MAC 9.
Furthermore, watercore was most prominent in fruit from trees on M.27 EMLA and
MAC 24 and least prominent in fruit from trees on MAC 9. This relationship
suggests that there may be significant differences with respect to the timing
of fruit ripening, but soluble solids and watercore are not very accurate
indices of fruit ripening.

During the course of ripening, apples exhibit a very rapid rise in the
biosynthesis of ethylene, a gaseous plant hormone. Within the core area the
concentration of ethylene rises with the increase in biosynthesis, providing a
very accurate means of comparing the times of ripening. Figure 1 shows the
internal ethylene concentration of apples from trees on M.27 EMLA, M.7 EMLA,
and MAC 9. Other rootstocks were deleted from the graph to avoid confusion,
but were roughly grouped into 3 patterns. Generally, M.27 EMLA (along with
Ott.3, M.9, and M.9A EMLA) encouraged the earliest increase in internal
ethylene. M.7 EMLA (along with M.26 EMLA, MAC 24, and OAR 1) resulted in a
somewhat later rise, and MAC 9 delayed the increase in internal ethylene.

Ethylene (ppm)

10 h

2 -

M.27 EMLA

M.7 EMLA

— *—
9/15

MAC 9

9/20

9/30

10/5

Figure 1. The internal ethylene concentration of Starkspur Supreme Delicious
fruit immediately after harvest from trees on MAC 9, M.7 EMLA, or M.27 EMLA.

Figure 2 shows the moan internal ethylene concentration for all harvests,
and it is obvious that M.27 fclMLA and Ott.3 resulted in higher levels and MAC 9

0.8

Ethylene (ppm)

0.0

Ott.3 M.7E M.9AE M.26E M.27E M.9

ROOTSTOCK

MAC9 MAC24 OARl

Figure 2. The mean, internal ethylene concentration of fruit harvested
September 15, 20, 25, and 30 from Starkspur Supreme Delicious trees on the
rootstocks included in this study. E refers to those rootstocks derived from
EMLA clones. Bars with different letters represent means that are
significantly different at the 5 % level (Duncan's New Multiple Range Test).

resulted in lower levels. These data confirm the effect of these rootstocks on
ripening, showing a significant delay in the rise in internal ethylene caused
by MAC 9 and enhancement caused by M.27 EMLA and Ott.3. Additional
confirmation is provided by the data in Figure 3. This graph shows the
postharvest ripening rate of fruit from trees on the various rootstocks. Fruit
from trees on MAC 9 ripened the slowest and those from trees on M.27 EMLA
ripened fastest, suggesting that the fruit from MAC 9 were less mature when
harvested than those from M.27 EMLA.

The ethylene measurements support the suggestion of the soluble solids and
watercore data that M.27 EMLA encouraged earlier ripening, whereas MAC 9
delayed ripening.

Cone lusions

The results from the first year of this study suggest that rootstocks can
alter fruit size, fruit quality (in terms of soluble solids and the incidence
of watercore), and the time of fruit ripening. In 1986 M.9 resulted in the

largest fruit, while M.27 EMLA and OAR 1 resulted in the smallest fruit.
Ripening was enhanced by M.27 EMLA, resulting in higher soluble solids levels,
more watercore, an earlier increase in internal ethylene, and faster post-

Days to 1 ppm Ethylene

Ott.3 M.7E M.9AE M.26E M.27E M.9

ROOTSTOCK

MAC9 MAC24 OARl

Figure 3. The mean, postharvest ripening rate (days to reach 1 ppm internal
ethylene) of fruit harvested September 15 and 20 from Starkspur Supreme
Delicious trees on the rootstocks included in this study. E refers to those
rootstocks derived from EMLA clones. Bars with different letters represent
means that are significantly different at the 5 % level (Duncan's New Multiple
Range Test).

harvest ripening rate. MAC 9 delayed ripening, resulting in lower soluble
solids levels, less watercore, a later increase in internal ethylene, and a
slower postharvest ripening rate. Study of these effects will continue in 1987
to confirm the results presented here.

Are rootstock effects on fruit ripening of commercial significance? The
delay that may be provided by MAC 9 (Mark) may only be a few days, but it may
be of some help in expanding the harvest season for a single cultivar. Strains
of some cultivars are now available which ripen somewhat earlier than normal.
If these strains are combined with rootstocks which encourage earlier ripening
and the standard strains are combined with rootstocks, like Mark, which delay
ripening, significant expansions of the harvest season may be obtained. If
Alar* is not available for drop control in the future, it will be necessary to
use techniques like the one suggested here for cultivars such as Mcintosh to
allow harvest of the entire crop.

10
Literature Cited

1. Bramlage, W. J. and W. J. Lord. 1967. Watercore and internal breakdown
in Delicious apples. University of Massachusetts Cooperative Extension
Service Publication No. 11.

2. Fallahi, E., D. G. Richardson, and M. N. Westwood. 1985. Quality of
apple fruit from a high density orchard as influenced by rootstocks,
fertilizers, maturity, and storage. J. Amer. Soc . Hort . Sci. 110:71-74.

3. Fallahi, E., D. G. Richardson, and M. N. Westwood. 1985. Influence of
rootstocks and fertilizers on ethylene in apple fruit during maturation
and storage. J. Amer. Soc. Hort. Sci. 110:149-153.

4. Hewetson, F. N. 1944. Growth and yield of Mcintosh apple trees as
influenced by the use of various intermediate stem pieces. Proc . Amer.
Soc. Hort. Sci. 45:181-186.

5. Lord, W. J., D. W. Greene, R. A. Damon, Jr., and J. H. Baker. 1985.
Effects of stempiece and rootstock combinations on growth, leaf mineral
concentrations, yield, and fruit quality of 'Empire' apple trees. J.
Amer. Soc. Hort. Sci. 110:422-425.

6. Perry, R. L. and D. R. Dilley. 1984. The influence of interstem on
ripening indices of 'Empire' apples. Compact Fruit Tree 17:50-54.

7. Wallace, T. 1930. Factors influencing the storage qualities of fruit.
Proc. 1^*- Imperial Horticultural Conference, London.

*****

P(M10L0GICAL PARAGRAPH

Pruning Well-feathered Trees at Planting

William J. Lord

Department of Plant and Soil Sciences

University of Massachusetts

If you receive well-feathered trees from the nursery, it is important to
leave as many favorably positioned branches on the trees as possible, because
when all but 2 or 3 branches are removed, these tend to grow very vigorously
and develop narrow crotch angles when growing conditions are favorable. Head
the trees at 39 inches, or 10 to 12 inches above the highest, useful branch, if
the tree is well feathered. Do not head the branches, or remove any more low
branches than necessary. Heading adds to the problem of excessive vigor on
vigorous cultivars and delays production. Low branches contribute to the total
leaf surface of the tree. Low branches and extra scaffold limbs can be removed
in subsequent years.

A REPORT ON THE 1986 MASSACHUSETTS APPLE IPM PROGRAM

William M. Coli, Daniel R. Cooley, Kathleen Leahy, and Ronald Prokopy

University of Massachusetts

Acknowledgements: We would like to thank Keith Bohne , Bill and Henry
Broderick, Dana Clark, William Flint, Jesse and Wayne Rice, Ed Roberts, and
Tony Rossi for their cooperation. We also thank Glenn Morin and Robin Spitko
(New England Fruit Consultants) for their scouting reports which we included in
the weekly pest message on several occasions, and for the harvest injury data
in Table 1. Special thanks to Sue Butkewich and Tom Green.

Program funding was provided in part by U.S.D.A. (Smith-Lever 3(d) Pest
Management), the Massachusetts Department of Food and Agriculture, and grower
contributions. Individual grower support of the Apple IPM program and the Pest
Alert messages totalled $2870 in 1986, an increase from 1985. In addition, the
Massachusetts Fruit Growers Association, Inc. provided a grant of $1,600 which
was used to replace the aging IPM vehicle. Our "new" vehicle, which we use to
travel to monitored orchards and research sites, is a 1983 Ford LTD, and has
already begun to develop a sticky trunk. We sincerely wish to thank the
growers and the MFGA for their continued interest in and support of the
program.

Five commercial orchard blocks (plus a San Jose scale-infested commercial
block in Lancaster) and one block at the Horticultural Research Center (HRC)
were monitored weekly for arthropods and pathogens affecting fruit trees. Scab-
infested leaves which had been placed in wire cages at these 6 sites in March
were collected weekly and examined using squash mounts and counts of mature
ascospores, to determine apple scab spore maturity. In addition, temperature
and rainfall were recorded at the Horticultural Research Center (HRC), and
other pest information was gained by occasional orchard visits and reports
from Sue Butkewich, Tom Green, growers, Extension workers in other states, and
private-sector consultants.

This information was used to reply to grower calls and write twice-weekly
Entomology Pest Messages from April 8 to September 10. Plant Pathology messages
were written weekly during the primary scab season, and in response to observed
problems afterwards. Messages initially were transmitted to regional agents via
the University computer's mail program, but after August 1 were shifted to a
grant-funded, microcomputer-based, bulletin board system (BBS) called INFONET.

Entomology and Plant Pathology staff made a combined total of about 100
orchard site visits during the year, assessing pest problems faced by large and
small commercial orchardists. Staff also gave 27 Extension talks at grower and
other group meetings and 2 talks at professional association meetings, and
authored or co-authored 5 Fruit Notes articles and several journal or
proceedings articles. Entomology staff again cooperated with Dr. Rick Weires,
Hudson Valley Lab, on the Annual March Message. Bill Coli gave an invited talk
at the 29^*^ annual meeting of the International Dwarf Fruit Tree Association,
entitled "Techniques of Integrated Pest Management for Commercial Orchards."
Plant pathology initiated cooperative research on delayed, early-season
spraying with Dr. William MacHardy of the University of New Hampshire and Dr.
David Rosenberger, Hudson Valley Cooperative.

At 4 Twilight meetings in each of the 3 regions, growers were provided
with extensive IPM training including 2 hours at each session covering sprayer
calibration using the Tree-Row-Volume method. These calibration sessions
provided a total of about 450 grower-training-hours, all suitable for pesticide
applicator certification credits. A 5-page handout titled "Calibration of
Orchard Sprayers Using the Tree Row Volume Method" prepared by entomology staff
was distributed at these meetings. This information is also being incorporated
into a computerized expert system which should be publicly available in the
near future. We would like to acknowledge the support and assistance of Mr.
Bill Doe, Doe Ag. Sales, and Mr. Rick Clark, Orchard Equipment and Supply, who
provided substantial expertise in fine-tuning the calibration of several
diverse types of sprayers. We also would like to acknowledge the contribution
of the Regional Agents who assisted in presenting this material at the twilight
meetings .

Fungicide, insecticide, and insect growth regulator trials were again
performed at the HRC and at grower sites, testing chemicals which may be or
presently are a component of commercial spray programs. Evaluation of pesticide
effects on mite predators continued as did evaluation of disease-resistant
apple cultivars. A commercial test block of disease-resistant cultivars planted
in a randomized block design was established at the Rice farm in Wilbraham.
This planting is intended to assess the feasibility of using no fungicides and
a minimum of insecticides in a commercial setting, and to define further
horticultural characteristics and marketability of these cultivars.

Related Entomology research and adaptive studies continued to focus on
evaluation of selective, relatively non-toxic pesticides and development of
monitoring traps for Tentiform Leafminer, on timing of plant bug injury and
pesticide treatment for plant bug, and on the behavioral ecology of the Apple
Maggot Fly and the Plum Curculio. Other Entomology studies involved a test of
several visual traps for monitoring the Walnut Husk Maggot (an occasional peach
pest), a project to collect and identify unusual mite predators first found
last season in a low-spray orchard in Stow, MA, and, in cooperation with Dr.
Alan Eaton, University of New Hampshire, a survey to determine the distribution
in Massachusetts of Psylla mali , the European Apple sucker. P . ma 1 i is not
found as a pest in commercial orchards, but appears to be expanding its range
and may become a pest in commercial blocks in the future.

Insect/Mite Pest Status and Harvest Injury, 1986

Tarnished plant bug - TPB was once again the number one cause of insect
injury in the state's commercial apple orchards. In one block we visited
weekly, no pre-bloom insecticide was applied, and on-tree injury reached 4%.
However, most "dimples" were in or near the calyx, and would not likely have
resulted in fruit downgrading.

Plum curculio - Extremely favorable weather in late May caused PC to

emerge in most areas over a very short period of time, allowing some growers to

control PC with one insecticide application. In a few locations, however, PC
egglaying scars were seen in late June and early July.

Apple maggot fly - Trap captures continued this year into October in all
areas of the state, although overall numbers of AMF captured were not high, and
only one Extension-monitored block sustained any injury. Again this year peak

captures occurred in September in commercial blocks and in Dr. Prokopy's
orchard.

Table 1. Percent insect-injured fruit in on-tree surveys of 53 commercial
blocks, 1986, compared to orchard harvest injury averages from 1978-1985.

Insect pest

Percent injury^

1986

1978-1985

Tarnished plant bug
European apple sawfly
Plum curculio
San Jose scale
Leafrollers
Green fruitworms
Apple maggot fly
Other

0.83
0.01
0.75
0.11
0.02
0.03
0.05
0.02

1.74
0.40
0.51
0.74
0.03
0.08
0.06
0.01

^Data provided by New England Fruit Consultants. Sample consisted of 50 fruit
per tree on 6 to 16 trees per block, depending on block size.

Apple leafminers - Sticky, red, visual traps again were very useful in
predicting potential LM problems prior to bloom. Traps in 3 of 6 blocks
indicated the need to treat, later borne out by counts of sap-feeding mines. In
2 other blocks, overwintering generation moth captures remained just below the
provisional action threshold (12 moths per trap), and first and second
generation mines likewise never exceeded the economic injury level. In one of
these blocks (which also sustained high levels of white apple leafhopper injury
and received no Alar®) we noted a higher level of pre-harvest drop than was
seen in other monitored sites.

White apple leafhopper - White apple leafhopper was again a problem at
many sites in 1986, especially where l^'- generation activity was not noted and
controlled, or where only organophosphate insecticides were used against the
OP-resistant leafhoppers. A few blocks experienced serious, late-season WAL
buildup. Also, see later section on potato leafhopper.

Mites - In most orchards mite numbers were very low this year, possibly
due to frequent, heavy rains throughout the summer. A. fallacis predator
numbers were very high in all locations compared to recent years, and seemed to
be thriving despite the shortage of red mite adults.

Disease Situation

The 1986 season was characterized by extreme disease pressure largely
caused by prolonged wet weather and low temperatures. The major efforts of the
program were to monitor Venturia inaequalis ascospore maturity from April

through mid-June, to develop weekly messages and distribute them to Regional
Fruit Agents, to test new ergos terol-synthesis inhibiting fungicides for
potential use in the program, to continue with work on disease-resistant
apples, and to participate in grower training sessions for sprayer calibration
and disease-management information.

Leaves for the apple scab maturity assay were collected from an abandoned
orchard in November, 1985, placed in hardware-cloth cages, and left out in a
non-sprayed orchard over the winter. These cages were distributed to the 6
sites in March. Weekly collections were made by Kathleen Leahy, Jim Williams,
and Bill Coli. Leaves were then examined, squash mounts prepared, and counts of
mature ascospores made.

Squash mount data indicated that primary season lagged behind tree
development by up to 2 weeks. This meant that early season sprays were not
needed. In most areas, fungicide applications could have been delayed until
half-inch green or tight cluster at the earliest. In fact, no fungicides
probably were necessary until bloom this year. Wetting periods monitored at
Belchertown showed that there were no Mill's infection periods before May 7,
because during wet periods weather was too cool for scab development. At this
time most trees were in early bloom. There were several heavy infection periods
through the rest of May. A heavy wetting period (72 hours) occurred June 5-8,
and the effects of this are still being discussed. Scab development on late
terminals during the end of June suggested that there was a primary infection
period at the beginning of the month, and that the maturity evaluations had
estimated the end of the season before it had occurred. The alternative
suggestion is that during mid-May, primary infections occurred, and during the
heavy rains in early June, secondary scab was spread. Scouting in the tops of
trees showed lesions on early terminals and clusters, indicating that these
infections had occurred in mid-May. Because of frequent rains, extreme
pressure continued through the summer, causing greater than normal fruit scab
in some orchards.

Pest messages have stressed the need to scout orchards until infections
which might have occurred have had a chance to show up. During this period,
sprays should be applied as they were during primary season. However, some
growers immediately reverted to a reduced frequency and/or rate in their spray
schedule at the announced termination of primary season. In our tests, such a
reduction this year resulted in terminal scab infections of the type reported
around the state. This confirms our original recommendation: after the end of
primary season, orchards must continue to be sprayed on a primary schedule for
a period sufficient to allow any primary infection to be visible.

Other infections appeared to be caused by a failure to spray before or
immediately after critical infection periods in May, or by a failure to cover
the tops of large trees. Large trees were infected much more frequently than
properly pruned trees on dwarfing rootstocks. Scouting the tops of trees
revealed primary infections better than scouting other locations.

Tests at the HRC also looked at the efficacy of 3 ergosterol-inhibit ing
(EI) fungicides, Rubigan'" (Elanco) , Nustar'" (Dupont), and A-815'" (Uniroyal)
and compared them to a standard dithiocarbamate, Manzate™ 200. In some
treatments, the EI compounds were combined with the Manzate. In general,
sterol-inhibit ing fungicides were better than Manzate at controlling primary

scab. Nustar was superior to other materials. These materials can be applied
on an after-infection basis up to 96 hours following the initiation of an
infection. Next season, the upper limits of this time will be tested. In
addition, an application of one or more of these materials will be made this
fall to determine whether they have any effect on the ability of the fungus to
overwinter and produce ascospores in the spring. The tests at the HRC
represented a 150% increase over such tests in previous years.

There were no reports this year of the bud blast or cankering attributed
to fire blight on Marshall Mcintosh. The summer may have been too cool for
development of the disease, though fire blight did show up in at least one
commercial orchard. Alternatively, dormant copper or Bordeaux treatments or
in-season streptomycin may be alleviating the problem.

New or Unusual Outbreaks

Potato leafhopper - Widespread leaf yellowing of apple throughout
Massachusetts has been identified by New York state entomologists as injury
caused by the potato leafhopper. Leaf injury, a diffuse yellowing of
consecutive terminal leaves, results from PLH feeding, during which leafhoppers
inject a toxic saliva. Injury shows up later, often after leafhoppers have
left. With no insects present, PLH injury can easily be mistaken for nutrient
deficiency. PLH does not overwinter in the region, but is "imported" from
southern states as storms move up the coast. Because the summer of 1986 was
characterized by a greater than normal frequency of such storms, PLH numbers on
several crops were unusually high.

Catfacing insects on peaches - Catfacing continued well into the summer on
peaches in many locations this year, with injury occurring at one monitored
site in early August. The causative agent is not known, although a rather
damaged specimen which may have been oak hickory plant bug showed up on an AMF
sphere in late July. We will be monitoring the situation closely in 1987 to
determine if other pests such as stink bugs might be causing this injury.

European corn borer - A grower located close to a corn field experienced
late season damage from ECB - larvae tunneling into the calyx and through the
core of the fruit. Growers in similar situations would be well advised to
monitor ECB populations in August and September. Also, early in the season,
one grower reported damage to terminal growth of young trees apparently caused
by an insect larva which was collected and tentatively identified as ECB.

Plans for 1987

We will be increasing the number of monitored orchards from 6 to 10 in
1987; two of these sites will very likely be low-spray orchards. In addition,
we will be monitoring a number of peach and pear blocks for borers, catfacing
insects, psylla, and peach X-disease as well as other problems which may become
apparent .

The INFONET computerized bulletin board, operated in cooperation with Dr.
Wesley Autio, Department of Plant and Soil Sciences, will be maintained and
expanded in 1987. This BBS is the primary means of disseminating topical pest
management and horticultural information, pesticide registration news, meeting
dates, etc. to regional agents and other interested parties. INFONET will

continue to be directly accessible to growers with telecommunication ability.
The BBS number in Amherst is 413-545-4717. For information or a user manual,
please call Bill Coli or Kathleen Leahy at 413-545-2283 or Wes Autio at 413-
545-2244.

We propose to continue most 1986 activities, including: monitoring
weather, pathogens, arthropods, and tree development in 10 commercial blocks,
writing twice-weekly pest messages, presenting 4 grower training sessions in
each of the 3 regions, performing adaptive studies and pesticide trials,
authoring extension and other publications, and generating outside funding. In
addition, we plan to provide continued support of the National Park Service IPM
Program at Adams National Historic Site, which will generate $500 to partially
support the Apple IPM technician. If 2 grant applications we have submitted
are approved, we will also be initiating a large-scale study in commercial
orchards on the influence of ground cover on mite predator prey interactions
and buildup of scab inoculum and a study aimed at implementing very low spray
programs using traps for controlling directly apple maggot flies.

Calibration will be emphasized, although not as intensively as in 1986.
Every attempt will be made to coordinate Entomology and Plant Pathology
scouting, with increasing emphasis planned for looking for disease incidence in
commercial and abandoned orchards.

We plan to develop computerized expert systems to diagnose and advise on
problems. Initially, these will be for use by regional agents, though it is
hoped that growers will have access to them in the near future through INFONET.
At present, we have initiated work on root disorder diagnostics, fruit
disorders diagnostics, scab fungicide application recommendations, and sprayer
calibration. This work is also supported in part by the College of Food and
Natural Resources, and in part by a Public Service Endowment from the
University .

POMOLOGICAL PARAGRAPH

Early, Heavy Cropping of Apples

William J. Lord

Department of Plant and Soil Sciences

University of Massachusetts

Early, heavy cropping of apple trees is not always desirable when trees
are planted at wide spacings. Early, heavy cropping may stunt the trees. This
situation has been observed in a row of Cortland on M.26 with the severity of
stunting varying considerably within the row. Therefore, we may find that in
some instances heading back cuts on the extension growth of the central leader
and on shoots of the scaffold (framework) branches is desirable. This
procedure will stiffen the central leader and scaffold branches, promote
growth, and delay fruiting. An alternative to heading cuts is defruiting.

17
RESULTS OF 1986 CHEMICAL THINNING TRIALS ON MCINTOSH

Duane W. Greene and Wesley R. Autio

Department of Plant and Soil Sciences

University of Massachusetts

Chemical thinning is one of the most critical activities undertaken by
apple growers each year. Effective thinning can mean the difference between
profit and loss not only the year of application but also the following year.

There have been no new chemical thinning agents registered in
Massachusetts in more than 20 years. However, during this period of time there
has been a steadily increasing demand for larger apples. We are continually
looking for new and better thinning agents, but until these are found and
registered it will be necessary to use more effectively those thinning agents
that are presently available.

Experiments were initiated at the Horticultural Research Center in
Belchertown in 1986 with two goals in mind: 1) evaluate the effectiveness of
several thinning treatments and combinations in an attempt to identify
promising treatments for future recommendations, and 2) determine the
importance of bloom intensity on final fruit set following a chemical thinning
treatment .

Experiment One

Mature Mcintosh trees (M.7 rootstock) with a heavy bloom were selected for
Experiment One. Thinning treatments were applied 16 days after full bloom on
May 26, 1986, when fruit diameter was approximately 10 mm. Treatments used
were: naphthaleneacetic acid (NAA) at 5 or 7.5 ppm and benzyladenine (BA) at
50 ppm. These were applied alone as a dilute spray or in combination with 1
lb. carbaryl (50 % WP) per 100 gal. One group of trees received no chemical
thinning spray and one received only carbaryl. After June drop all fruit on
previously tagged limbs were counted and fruit set was calculated. A 30-apple
sample was taken at harvest, weighed, and evaluated for percent color, flesh
firmness, and soluble solids (sugars) content.

Generally, a fruit density of about 5.5 to 6.0 fruit/cm limb circumference
on Mcintosh is considered to be ideal, and all treatments thinned when applied
alone, although only BA at 50 ppm and NAA at 7.5 ppm thinned adequately (Table
1). When carbaryl was combined with NAA or BA additional thinning occurred.
NAA at 7.5 ppm, BA, and carbaryl alone increased fruit size. Size was
increased further when carbaryl was added. No chemical thinning spray
influenced flesh firmness, soluble solids, red color, or seed number.

Because of its detrimental effects on mite predators the use of high rates
of carbaryl is discouraged. Attempts are being made to minimize the amounts
used. Although the effectiveness of carbaryl is somewhat concentration
independent, rates of 1/4 lb per 100 gal. or below may be insufficient to thin
adequately by itself. NAA is a very effective thinning agent but it is also
the compound most likely to over-thin. Lower rates of NAA are frequently
chosen to reduce the chance of overthinning. Therefore, the most satisfactory

chemical-thinning treatment would be one using a moderate level of carbaryl in
combinations with NAA. Acceptable thinning should be achieved without causing
overthinning or severely depressing the predator mite population.

Table 1. Effects of naphthaleneacetic acid (NAA), benzyladenine (BA), and
carbaryl (50 % WP) on fruit set and fruit weight of Mclntosh/M.7 apple trees.

Fruit/cm limb circumference Fruit weight (g)

Carbaryl (1 Ib./lOOgal.) Carbaryl (1 Ib./lOOgal.)

13.6

8.6

6.2

4.1

9.3

3.8

6.7

5.9

130

147

153

174

142

156

150

164

Treatment^ (-) (+) (-) (+)

Control
BA, 50 ppm
NAA, 5 ppm
NAA, 7.5 ppm

Average 8.9 **^ 5.6 144 ** 160

^Treatments were applied as a dilute spray on May 26, 17 days after full bloom.
NAA was applied as Fruitone N" and carbaryl as Sevin" (50 % WP) .

YTreatment effects on fruit set or weight were significantly different (5 %
level, Duncan's New Multiple Range Test) if not followed by a common letter.

^The effects of carbaryl on fruit set and fruit weight were significant at the
1 % level (Duncan's New Multiple Range Test).

BA is in the developmental stages as a chemical thinner. It is the only
chemical used alone that adequately thinned Mcintosh. It has performed equally
well as a thinner over the past 5 years on Mcintosh as well as on other
cultivars. BA presently is being sold as a branching agent on Christmas trees
and is also 50% of the active ingredients of Promalin'". We will continue to
evaluate this compound.

Experiment Two

A block of 16-year-old Mcintosh on MM. 106 was selected, and just prior to
bloom 70 limbs were tagged and the blossom clusters were counted. Limbs were
selected that had a wide range of blossom densities, some having as few as 15
and others having as many as 350. A dilute thinning spray containing 2.5 ppm
NAA and 1 lb. carbaryl per 100 gal. was applied with an airblast sprayer on May
27, 16 days after full bloom. Fruit set was determined at the end of June
drop .

It was found that the greater the number of blossom clusters at bloom the
more fruit that remained after June drop (Figure 1). However, the point that
we would like to e;iipluisize is that it requires a large increase in the amount
of bloom on a limb to cause a relatively small increase in fruit number. For
example, if the bloom on a limb was increased from 5 to 10 blossom clusters per
cm limb circumference, the fruit set after thinning would increase only from
about 5.5 to 6.5 fruit per cm limb circumference. NAA at 2.5 ppm plus J lb.
carbaryl per 100 gal. is a moderate thinning treatment, and adequate thinning
was obtained on limbs with blossom densities up to 10 to 12 blossom clusters
per cm limb circumference. NAA at 5 to 7.5 ppm plus carbaryl would have been a
better choice for the limbs having a heavier bloom.

Fruit per cm Limb Ore.

■

•
•

•

10
5

•

■
■

i^- •

• •
«• •

1 I

•
•

•

• •

•
•

•

•
•

• •

5 10 15 20 25

Blossom Clusters per cm Limb Giro.

Figure 1. Effect of blossom cluster density on final fruit set of Mcintosh
apples following a chemical thinning spray of NAA at 2.5 ppm plus 1 lb carbaryl
(50 % WP) per 100 gal.

Although blossom density does influence fruit set, treatments can be
selected that will operate effectively over a relatively wide range of
densities. NAA at 3 ppm plus carbaryl at 1 lb. per 100 gal. should be
effective on trees with low to moderate bloom, whereas NAA at 5 to 7.5 ppm plus
carbaryl at 1 lb. per 100 gal. would be more appropriate on Mcintosh trees with
a moderate to heavy bloom.

*****

20
TIMING THE TARNISHED PLANT BUG: A TALE OF FRUSTRATION

Ronald J. Prokopy, Susan L. Butkewich, and Thomas A. Green

Department of Entomology

University of Massachusetts

In 1976 we began what turned out to be 11 consecutive years of research on
(a) the stages of plant development during which tarnished plant bug (TPB)
injury to apple is initiated, (b) the most efficient method of monitoring the
appearance of plant bug adults, and (c) the efficacy of various pesticides for
controlling plant bugs. In 4 previous issues of Fruit Notes [43(2) : 10-14,
44(2) :l-5, 45(3):15-18, and 45(4)13-14], we reported our results of the first 4
years. In brief, we found that (a) apple flower buds, blossoms, and developing
fruit are susceptible to TPB feeding injury from silver tip to about one month
after petal fall, (b) susceptibility to bud abortion (abscission) is greatest
from silver tip until tight cluster, while susceptibility to fruit injury
(dimples and/or scabbing) is greatest from tight cluster to a month after petal
fall, (c) a 6 X 8 inch sticky white rectangle trap placed at knee height near
the periphery of the tree offers an effective method of monitoring the
abundance of TPB adults, (d) capture of 2.5 or more adults per trap from silver
tip through tight cluster or 4.2 per trap from silver tip through midp


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