Full text of "Fruit notes of New England"

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Volume 64, Number 1
WINTER ISSUE, 1999

Table of Contents

A Note from the Editors

Making Integrated Mite Control Work in Northeast Apple Orchards

Establishment and Spread of Released Typhlodromus pyri Predator Mites
in Apple Orchard Blocks of Different Tree Size: 1998 Results

Budagovsky 9: A Summary of Fifteen Years of Trial

Editors:

Wesley R. Autio
William J. Bramlage

Publication Information:

Fruit Notes (ISSN 0427-6906) is pub-
lished the each January, April, July, and
October by the University of Massachu-
setts in cooperation with the other New
England state universities.

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Fruit Notes

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University of Massachusetts
Amherst, MA 01003

All chemical uses suggested in this publication are contingent upon continued registration.
These chemicals should be used in accordance with federal and state laws and regulations.
Growers are urged to be familiar with all current state regulations. Where trade names are
used for identification, no company endorsement or product discrimination is intended. The
University of Massachusetts makes no v/arranty or guarantee of any kind, expressed or
implied, concerning the use of these products. USER ASSUMES ALL RISKS FOR PERSONAL
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Issued by UMass Extension, John Gerber, Director, in furtherance of the acts of May 8 and June 30. 1914.
UMass Extension offers equal opportunity in programs and employment.

A Note from the Editors

Fruit Notes has been published for 63 years by pomologists at the University
of Massachusetts (actually at the Massachusetts Agricultural College in the
beginning). During these years, it has evolved considerably but always has focused
on issues of importance to fruit growers. Today's subscribers live primarily in New
England, but many are from other tree-fruit-producing states and several other
countries.

With this issue, the first of its sixty-fourth year, Fruit Notes is embarking on
new and exciting changes. First, the cover is redesigned, but most importantly it is
becoming Fruit Notes of New England. We hope to have regular contributions
from individuals in the other New England states.

Within the articles, the first evidence of this change is the discussion written
by Jan Nyrop on the use of mite predators. This paper, although not written by a
New England author, was presented at the 1999 Annual Meeting of the Maine
State Pomological Society. In fact, Fruit Notes subscription will be a benefit of
membership in the Maine State Pomological Society, and Fruit Notes will publish
papers presented at meetings of the Society.

The editors are excited about these changes and hope that they result in a
significant improvement in the quality of this pubUcation. If you have any
questions or comments, please contact us at the address provided inside the cover.

Fruit Notes, Volume 64 (Number 1), Winter, 1999

Making Integrated Mite Control Work in
Northeast Apple Orchards

Jan P. Nyrop

Department of Entomology, Cornell University, NYSAES, Geneva, New York

European red mites (ERM), Panonychus idmi,
feed on leaves of apple trees and thereby interfere
with photosynthesis and production of carbohy-
drates. At high levels, ERM damage to apple
leaves reduces fruit yield and quality. As a general
rule, keeping ERM numbers below 2.5 per leaf
before July, below 5 per leaf during July, and
below 7.5 per leaf in August will prevent economic
losses from this pest.

Three strategies can be used to control ERM in
apple orchards. First, protectant miticides (e.g.,
dormant oil or an ovicide) can be applied early in
the growing season. Second, pest mite numbers
can be monitored and miticides applied if densities
exceed threshold levels. Third, natural enemies
that feed on ERM can be encouraged and managed
to constrain pest mite numbers. Strategies based
solely on miticides are relatively expensive and
eventually lead to the development of resistance by
ERM to the miticides. With the help of natural
enemies, the cost of managing ERM in apples can
be greatly reduced and resistance delayed.

Insect and mite predators, including several
species of phytoseiid mites, stigmaeid mites such as
Zetzellia malt, and ladybird beetles, feed on ERM.
Phytoseiid mites are the most effective of these
predators in the Northeast. Several species of
phytoseiid mites, including Amhlyseius fallaas,
Typhlodromus pyri, T. occidentalis, T. vulgaris,
and A. cucumeris, can be found in commercial
orchards. Species cannot be identified in the field
because they are so similar in appearance. They
are only distinguishable through microscopic
examination of the arrangement of the setae
(hairs) on their bodies. T. pyri and A. fallacis are
the two most common species in Northeast
orchards. Of the two, T. pyri is better able to
regulate ERM populations. This is the species that
should be established and maintained for

biological mite control in Northeast orchards. In
this article I answer three questions: First, why is
it that T. pyri is such an effective predator?
Second, is T. pyri an effective predator throughout
the northeast? Third, how can you make use of
this natural enemy to provide cost-free mite
control?

Why is Typhlodromus pyri such an effective
predator? For many years A. fallacis was

promoted as an effective biological control agent
for ERM. In truth, A. fallacis gives sporadic and
unreliable ERM control, while T. pyri is highly
effective in this capacity. Differences in
effectiveness of T. pyri and A. fallacis as biological
control agents are rooted in their biologies.

T. pyri require approximately 32 days to
complete a generation, and have three to four
generations per year. They overwinter as mated
adult females on trees wherever they can find a
protective site (e.g., bark crevices, branches,
spurs). Adult females emerge from overwintering
sites on warm spring days before budbreak. The
adults live about 20 days and lay an average of 20
eggs starting as early as tight cluster or pink bud
growth stages. Eggs are usually laid on the
undersides of leaves along the midrib. The eggs
hatch in 1-3 days and resulting immatures are
nearly transparent and look like smaller versions
of the adults. Immatures and adults feed on a wide
variety of food sources, including pollen and rust
mites, along with ERM and two-spotted spider
mites (Tetranychus itrticae). An adult female will
consume one to two ERM adults or three to four
ERM nymphs per day. These predators do not
concentrate on leaves with large numbers of ERM,
unlike some other phytoseiids (e.g., A. fallacis). T.
pyri are relatively winter hardy and remain in the
tree even when ERM are scarce, feeding on
alternative food sources.

A. fallacis require 16 days for each generation,

Fruit Notes, Volume 64 (Number 1), Winter, 1999

with four ro six gcncr.UKnis per year. These
phytoseiids may also overwinter .is adults in trees
if prey are available to feed on m late siiinmer and
early fall; otherwise, they disperse from the trees
and overwinter in the ground cover. Occasionally,
they can be found in trees when HRM eggs start to
hatch just before bloom, but are usually scarce
until mid-July because of high winter mortality or
lack of ERM as a food source before bloom. Adult
A. fallacis lay twice as many eggs as T. pyri,
immatures and adults consume nearly a third more
ERM per day than T. pyrt, and immatures develop
into adults in a third of the time required by T.
pyri. A. fallacts feed mainly on spider mites.
Therefore, when prey mite numbers are low in the
trees, A. fallacis will disperse out of the trees to
locate another food source, possibly in the ground
cover. A. fallacis are more effective at reducing
high red mite populations than T. pyri, but this is
often after ERM have done considerable damage
to the leaves.

Based on generation time, oviposition rate,
and prey consumption, it would appear that T.
pyri is a less effective biological control agent than
A. fallacis. But the advantages T. pyri has over A.
fallacis are its greater winter hardiness, its use of
alternative food sources when ERM are not
present, and its tendency to remain in trees when
ERM are scarce. When ERM numbers are low, T.
pyri will stay in the tree canopy feeding on pollen
and rust mites, and will continue to be a presence
as ERM numbers start to rise.

Because A. fallacis are often absent from trees
or are in very low numbers in trees in early spring.

ERM often build to damaging levels bclorc A.
fallacis exercise control. I . pxri will consistently
maintain ERM populations at low levels provided
these predators are conserved. T. pyri usually
cannot control ERM populations in excess of five
to seven per leaf, and it can take 2-3 years for
sufficient numbers of 7. pyri to build in an orchard
to realize biological control. Once predators are
established, the benefits are great as the need for
miticides can be eliminated.

Data from an orchard at the New York State
Agricultural Experiment Station into which T. pyri
were released into two blocks of Delicious trees
will serve to illustrate the effectiveness of this
predator. In this orchard, no miticides were used
since 1991, fungicides have consisted of captan
and Nova, and pesticides have been restricted to
Imidan, Sevin, Bt, and Provado. Dynamics
between T. pyri and ERM were measured between
1992 and 1997. Results are summarized in Table
1. Since 1992 ERM numbers have been kept well
below threshold levels (500 mite days) and
predator numbers have steadily increased.
Averages shown here are the average of temporal
counts from June 1 to September 1.

Is Typhlodromus pyri an effective predator
throughout the northeast? Yes! Until recently, T.
pyri was thought to be common in eastern north
America only in central and western New York
and Nova Scotia. Therefore, in 1996 we

embarked on a project with cooperators in all the
New England states to introduce and establish T.
pyri throughout this region. There is no apparent
reason why T. pyri should not survive and thrive

Table 1. Summary

statistics for

European red

mite (ERM) and Typ^/oiirowMspyn in

two orchard block

s at G

eneva_,

Numbt

■rs are c

ensity per

eat".

Parameter

1992

1993

1994

1995

1996

1997

Maximum ERM

2.1

0.2

3.6

1.8

1.9

1.53

Mite days'

Average ERM

0.8

0.08

0.7

0.3

0.5

Minimum T. pyri

<0.1

0.2

0.1

0.3

0.1

Maximum T. pyn

0.1

0.9

0.6

1.4

1.9

2.8

Average T. pyri

0.02

0.5

0.3

0.9

1.3

' Mite days is the cumu

ative

densi

ty of mites. The

damage th

reshold is

500 mite

days.

Fruit Notes, Volume 64 (Number 1), Winter, 1999

(0
DC

Average

10-

® o

.1-

0°°® OCfe

ffl ® ® O

® ® ® ® e ® ®

1 1

Maximum

100

10^

in
ummer oil.

Carzol

' Check EPA and state registration status by contacting local Cooperative Extension representative. Registration
status is changing annually and is not universal across all state lines. Use of product names does not imply
endorsement of particular products. Read all labels for rates and timing.

Fruit Notes, Volume 64 (Number I), Winter, 1999

predators should be released in each target tree.

The fourth method of transferring T. pyri is
perhaps the easiest and does not carry the risks of
also moving unwanted pests that the three prior
methods have. Artificial overwintering sites for T.
pyri can be created by gluing burlap to the inside of
tree wrap. These composite bands, approximately
12 to 16 inches in length, are then placed on source
trees in early to mid-September by stapling them
around the tree bole and/or large scaffold
branches. In early December, these bands should
be collected, tightly rolled with a rubber band used
to hold them so, and placed in a sealed plastic bag
with a bit (ca. 1 in') of wet cotton. The bag should
be placed in an insulated storage container, which
in turn should be placed in a cold, though
protected, environment that will buffer large
temperature fluctuations. Ideally, temperatures
should be maintained right at the freezing point.
The following spring, the burlap bands should be
placed around recipient trees at around the half-
inch green bud growth stage. While the number of
predators that overwinter in bands is variable, as
many as 400 predators can be transferred in each
band. We suggest placing a single band on each
recipient tree if the bands were collected from trees
that harbored moderate to high numbers of T. pyri
(1-2 per leaf) the prior fall, and two bands in each
tree otherwise.

After a receiver orchard is inoculated with T.
pyri, it often takes 2 to 3 years for the predator
population to become abundant enough to
regulate ERM without the need for any miticides.
During this time, additional control measures are

often needed to keep ERM below damaging levels.
There are two key aspects to any strategy designed
to do so. First, early season dormant oil sprays
should be used to reduce ERM populations in the
spring. These oil applications have no deleterious
effect on T. pyri. Second, ERM numbers should be
monitored, and if densities exceed threshold levels,
a miticide that is not toxic to T. pyri should be used
to control the pest mites. Note that it is actually
desirable to have some pest mites in the trees after
inoculation with T. pyri because these plant-
feeding mites provide a food source for the
predators and foster faster predator population
growth.

A commonly asked question is, "How do you
know when there are enough T. pyri to effect
biological control?" This question is difficult to
answer. While predators can be seen in the field,
they are easy to miss, especially at low densities,
and their impact on ERM is dependent on which
species they are. Guidelines have been provided
for the ratio of predators to ERM needed to
achieve biological control; however, estimating
these ratios is not practical. Fortunately, all that is
required to determine if biological control is
working is to note whether pest mites remain
below threshold levels. This can be determined
without regard to predator abundance. A
procedure for determining whether ERM exceed
threshold levels is described in the appendix. If
pesticide regimes for all orchard pests can be
followed that allow T. pyri to survive, these
predators will become abundant enough to make
miticide applications unnecessary.

Appendix - Monitoring European Red Mite in Apple Orchards

Damage by European red mites (ERM) to
apple leaves is best related to cumulative mite
density, which is measured as mite-days. Apple
trees with a normal crop load can tolerate
approximately 500 mite-days before reductions in
fruit yield or quality occur. Therefore, one goal of
any mite monitoring program is to ensure that
miticide treatments are recommended so as to
prevent 500 mite-days from occurring. Another
goal of a mite monitoring program is to allow
biological control to take its course when mite

natural enemies (phytoseiid mites) are present. So,
a mite monitoring program should not recommend
intervention with pesticides when treatments are
not necessary. A final goal of a mite monitoring
program is to indicate when the pest population
should again be sampled to determine its status. If,
at the time of sampling, mite densities are very low,
then it is not necessary to sample the population
again in a short period of time. On the other hand,
if densities are currently close to but not greater
than a treatment threshold, the population should

Fruit Notes, Volume 64 (Number 1), Winter, 1999

Use this sampling
guide during June

Use this sampling
guide during July

Use this sampling
guide during August

0) 40

20-

10-

Treat

Sample in
7 days

GoO'
5

\^^'

^p^'^^

31
19

35
23

36
26

111

I I I I

Sample in 14 days I

I I I I

50 60 70 80

Leaves examined

100

i
1
1
1

i 1

t 1 i
1 1 1
1 1 i

1 ( ,.■>

70-

74 y

62 /I

Treat 1

66
55

60-

Sample in
7 days

1 i 1

1 1 i

B 50-

51
39

52 52/
39 /I

J 48

5 40-

1 i

1 1

43
29

^^'"

CO'

10-

Sample in 14

days ,

1 1

1 1
— I 1 —

20 30 40 50 60 70

Leaves examined

100

1 1

1 1
i 1

t 1
, Treat

i t

1 i

i 1

! 1

' '

' 1 :./

80-

1 1

82 V

70-

73
64

Sample in
7 days

60-

63 63/

50 /I

C/l

!■■■ ■ 1

1 I
1 1
1 1
1 1
1 1
1 1
1 1

1 .,

5 40-

44
31

!>'

^ 30-

a^-^

1 f
1 1
1 i

20-

1
1

Sample in
t 1
1 1

4 days 1
1 i
1 1
1 1
1 1

r — ' r— -J

10-

1 1

1
1

50 60 70

Leaves examined

100

Fruit Notes, Volume 64 (Number 1), Winter, 1999

be assessed again in a short period of time. The
monitoring program described here meets these
goals.

This monitoring procedure classifies ERM
density into one of three categories: 1 ) greater than
treatment threshold, indicating application of a
miticide is necessary, 2) less than treatment
threshold, but requiring assessment again in about
7 days, and 3) much less than a treatment
threshold and not requiring assessment again for
14 days.

ERM are small and often numerous. This
makes counting these pests a tedious and often
difficult task. For monitoring purposes, it is only
necessary to record the number of leaves infested
with one or more motile mites. A mathematical
relationship between the proportion of infested
leaves and actual density can then be used to
classify mite density. Because higher mite numbers
can be tolerated as the season progresses, three
sampling procedures are used at different times of
the growing season; one each for June, July, and
August with treatment thresholds of 2.5, 5, and
7.5 mites per leaf , respectively.

The sampling guides are used as follows:

1. Sampling trees from throughout the orchard

block, collect five intermediate aged leaves
from each of four trees. To make sure the
leaves are of an intermediate age, pick them
from the middle of the fruit cluster before July
and from the middle of fruit clusters or
terminals thereafter.

2. Using a magnifier, examine the top and bottom
surface of each leaf for motile mites (anything
but eggs), and keep track of the number of
leaves with mites on them.

3. When all 20 leaves have been examined,
compare this number with the numbers on the
decision guide. When the counts fall into any
of the shaded regions, sampling is terminated
and a decision to either "Treat", "Sample in 7
days," or "Sample in 14 days" is made. If the
counts fall in the region labeled "Continue
sampling" collect and examine groups of 10
leaves until the counts fall into one of the
shaded regions. If the number of leaves with
mites is equal to the values on the guide, use the
decision indicated by the value minus one (e.g.,
for the June chart, if 18 leaves have ERM after
examining 20 leaves, use 17 leaves with mites
and make a decision to "Continue sampling").

Fruit Notes, Volume 64 (Number 1), Winter, 1999

Establishment and Spread of Released
Typhlodromus pyri Predator Mites in
Apple Orchard Blocks of Different Tree
Size: 1998 Results

Ronald Prokopy, Starker Wright, and Jonathan Black
Department of Entomology, University of Massachusetts

Jan Nyrop, Karen Wentworth, and Carol Herring

Department of Entomology, Cornell University, NYSAES, Geneva, New York

Studies in New York, other states, and other
countries have shown that the predatory mite
Typhlodromus pyri, where established, can be
highly effective in providing season-long suppres-
sion of pest European red mites in commercial
apple orchards. Three of the reasons why T. pyri
is more reliable than the mite predator Amblyseius
fallacis in maintaining pest mites below injurious
levels year after year are its better ability to endure
cold winter temperatures, its better ability to with-
stand low relative humidity, and its better ability
to survive periods of short supply of pest mites as
food (as may occur in springtime). In Massachu-
setts, A. fallacis has been found present in about
90% of commercial apple orchards sampled since
1978. In contrast, T. pyri has been found present
in numbers large enough to be detected in fewer
than 10% of Massachusetts commercial apple or-
chards sampled since 1978.

In 1997, we initiated a program of introduc-
ing T. pyri into eight commercial apple orchards
in Massachusetts in which it was not previously
detected. Three of our aims were to (1) chart the
degree of establishment of T. pyri in each orchard
as affected by types of pesticide used; (2) chart the
rate at which T. pyri spread from trees on which
they were released to other trees in the same or-
chard blocks, as affected by tree size and planting
density; and (3) determine the impact of T. pyri on
pest mite populations. Our study was intended to
extend over a period of at least 3 years. In the Fall

1997 issue of Fruit Notes, we reported on our find-
ings from 1997, the first year. Here, we report on
our findings from 1998, the second year.

Materials & Methods

As indicated in the Fall 1997 issue of Fruit
Notes, our experiment was conducted in six blocks
of apple trees in each of eight commercial orchards.
Of the six blocks per orchard, two each contained
trees on M.9, M.26, or M.7 rootstock, designated
as small, medium-size, or large trees. One block
of each pair received first-level IPM practices,
wherein growers applied insecticides and fungicides
of their own choosing and timing of application,
which extended from April through August. The
other block of each pair received third-level IPM
practices, wherein the initial intent was that no
pesticides known to cause a moderate or high level
of harm to T. pyrt were to be used. These included
synthetic pyrethroid insecticides (at any time) and
EBDC fungicides (after mid-June). In addition,
after mid-June, no insecticides of any type was to
be used, and captan or benomyl were the only fun-
gicides to be used. There was no restriction on
type of miticide allowable for use in third-level
blocks, except for Carzol, which was not used.
Each block was comprised of 49 trees (7 rows of 7
trees per row) and of the cultivars Mcintosh, Em-
pire and Cortland. Third-level IPM is similar to
second-level IPM in focus on using biologically-

Fruit Notes, Volume 64 (Number 1), Winter, 1999

Figure 1 In July and August of 1998, abundance of T. pyri mite predators on leaves sampled from third-
level IPM blocks (in wtiich T. pyri were released on the center tree In mid-IVlay 1997) and first-level IPM
blocks (in which no releases of T. pyri were made).

Third-Level IPM Blocks. Low Tree Density

Sample Dale

Legend:

Third-Level IPM Blocks, Medium Tree Density

0.8

0.7

g <>«

0.3

0.2

^y^ ^

^^''^

^^"""^

^^^f"^^'^

/» 7/22 vs t/^

Sample Date

Third-Level IPM Blocks, High Tree Density

OB
OB
0.7

.- 0.5

0.3

}

/V__^

^^.^'"'''^

"^ ^^ '''

/8 7/22 a/s a/I

Sample Date

First-Level IPM Blocks. Low Tree Density

Sample Date

First-Level IPM Blocks, Medium Tree Density

"5 06

L_ 05

So.

3
02
01

7/8 7/22 a'S a/)9

Sample Date

First-Level IPM Blocks. High Tree Density

Sample Date

Center Tree

Center Row, Outer Trees

Outer Row, Center Trees

based pest management practices, but it embraces manner described in the Fall 1997 issue of ¥ruit

integration with horticultural concerns (such as tree Notes. No T. pyri were released in first-level IPM

size) as an added component. blocks. Three times during the summer of 1997

T. pyri were released onto the center tree of and four times during the summer of 1998 in each

each third-level IPM block in May of 1997, in the of the 48 blocks, we sampled 25 leaves from the

Fruit Notes, Volume 64 (Number 1), Winter, 1999

Figure 2. In July and August of 1998, abundance of A. fallacis mite predators on leaves sampled from thiird
level IPM blocks (in wfiich 7" pyri were released on the center tree in rr\\d-May 1997) and first-level IPM
blocks (in which no releases of T. pyri were made).

00
OS
07

ro 08

.-OS

Third-Level IPM Blocks. Low Tree Density

^^>

,^— -^-''^-— ^*

/o 7/22 a/s afi»
Sample Date

Legend:

Third-Level IPM Blocks, Medium Tree Density

07
? 06
.- 05

03
02
01

■ —

^— ^"^ ""^ ^ '

/a 7722 a/s Bfi

Sample Date

Third-Level IPM Blocks. High Tree Density

0.9
OB
0.7

1 °«

.- 05

Q- 04

0.3

0.2

0.1

_^— m * "

/B 7/22 8/5 a/1

Sample Date

Firsl-Level IPM Blocks. Low Tree Density

Sample Dale

First-Level IPM Blocks. Medium Tree Density

Sample Date

First-Level IPM Blocks, Higti Tree Density

Sample Date

Center Tree

Center Row, Outer Trees

Outer Row, Center Trees

center tree, 15 leaves from each of the two outer- Geneva, New York for the identification and count-
most trees in the center row, and 15 leaves each ing of pest and predatory mites. In all, more than
from the center tree in each of the two outermost 12,000 leaves were sampled in 1997 and more than
rows. The leaves were sent by overnight mail to 16,000 in 1998.

Fruit Notes, Volume 64 (Number 1), Winter, 1999

Figure 3. In July and August of 1998, abundance of European red mites on leaves sampled from tfiird-
level IPfVI blocks (in which 7". pyri were released on the center tree in mid-May 1997) and first-level IPfvl
blocks (in which no releases of r pyn were made).

Third-Level IPM Blocks. Low Tree Density

^/^-^

Sample Date

Third-Level IPM Blocks. Medium Tree Density

)

/a 7/22 a/s a^i
Sample Date

Third-Level IPM Blocks. High Tree Density

/B 7/22 a^s a/1
Sample Date

Legend:

First-Level IPM Blocks. Low Tree Density

-i^

y ""v^?-.

/ _,-^^'^^^^'"***«>^>

y , " ' ^^ ^ __ - > -^^'o*

"v"^""*--.^ v"^ '^

Y' '-^ s

Sample Date

First-Level IPM Blocks. Medium Tree Density

# per leaf

7/8 7/22 8/5 W19

Sample Dale

First-Level IPM Blocks. High Tree Density

1- 5

Sample Date

Center Tree

Center Row, Outer Trees

Outer Row. Center Trees

Results in third-level IPM blocks in 1997. Populations on

center trees in early July averaged greatest on small

As shown in Figure 1, T. pyri were found in (high density) trees, middle range on middle-size

low but detectable average numbers in early July (middle density) trees, and least on large (low den-

of 1998 on center trees in which they were released sity) trees. By the latter part of August, T. pyri on

Fruit Notes, Volume 64 (Number 1), Winter, 1999

center trees reached 0.4, 0.5, and 0.8 per leaf on
small, middle-size, and large trees, respectively. At
this time, T. pyri on the two outermost trees of the
center row averaged 0.8, 0.1, and 0.3 per leaf on
small, middle-size, and large trees, respectively, in-
dicating spread of T. pyri up and down the same
row in which they were released, particularly in
blocks of small trees. There was little or no de-
tectable spread of T. pyri onto center trees of the
outermost rows of blocks of medium-size and large
trees but detectable spread onto such trees in blocks
of small trees. In 1998, T. pyri were largely absent
or at most present in extremely low numbers in
first-level IPM blocks in which they were not re-
leased in 1997 (Figure 1).

As shown in Figure 2, by the latter part of
August of 1 998, A. fallacis had built to larger popu-
lations in first-level than in third-level IPM blocks
of both small and medium-size trees, although the
reverse was true in blocks of large trees. In con-
trast to T. pyri, which was detectable in third-level
blocks of all tree sizes in early July, A. fallacis was
not detectable in any blocks (either third- or first-
level IPM) until the latter part of July.

As shown in Figure 3, populations of European
red mites in 1998 were barely detectable during
July and August in either third- or first-level IPM
blocks of small or medium-size trees. They did,
however, reach substantial (though not damaging)
average numbers in both third- and first-level
blocks of large trees.

Table 1 provides information on the possible
influence of both type of pesticide used and abun-
dance of European red mites as prey on popula-
tion levels of T. pyrt in third-level IPM blocks. It
appears that abundance of European red mites had
less of an influence on buildup of T. pyri than did
type of pesticide used. For example, in Orchard
A, latter-August populations of T. pyri in 1998
averaged nearly double those of 1997, whereas in
Orchard H, latter-August populations in 1998 av-
eraged less than one-fourth those of 1997. Latter-
August populations of European red mites in 1998
averaged the same in both of these orchards. No
insecticide harmful to T. pyri was applied in third-
level IPM blocks in either Orchard A or Orchard
H in 1997 or 1998. In 1997, neither orchard re-
ceived any EBDC fungicide or Agri-Mek as a miti-
cide. In 1998, Orchard H received three applica-

tions of EBDC fungicide and one application of
Agri-Mek, as opposed to use of only one applica-
tion of EBDC fungicide and no Agri-Mek in Or-
chard A. These combined data suggest that either
the greater number of EBDC applications or the
use of Agri-Mek was responsible for the rather
sharp decline of T. pyri in 1998 in Orchard H.

Data from other orchards (Table 1) support the
lack of strong influence of abundance of European
red mites on extent of T. pyri buildup or decline
from 1997 to 1998 (compare Orchard D with
Orchard A) and the lack of strong influence of
number of applications of EBDC fungicides (com-
pare Orchard H with Orchard B, and Orchard E
with Orchard A). Instead, it appears that use of
Agri-Mek in third-level IPM blocks was the prin-
cipal factor responsible for the decline in abun-
dance of T. pyri from 1997 to 1998 in third-level
blocks in some orchards (compare Orchards D, E,
G, and H, all of which experienced a decline by an
average amount of about 75% in T.pyn from 1997
to 1998 and all of which received Agri-Mek in
1998, with Orchards A, B, C, and F, all of which
experienced an increase in T. pyri by an average
amount of about 240% from 1997 to 1998 and
none of which received Agri-Mek in 1998).

Conclusions

Combined data from 1997 (reported in the Fall
1997 xssutoi Fruit Notes) and 1998 (reported here)
indicate that T. pyri mite predators released in 1997
became firmly established and proliferated in 1998
in those third-level IPM blocks that in 1998 did
not receive Agri-Mek as a miticide. Our evidence
suggests that abundance of European red mites as
prey of T. pyri was a less important factor affect-
ing population increases or decreases of T. pyri than
was the effect of Agri-Mek per se on T. pyri. Our
findings also indicate that by the end of 1998, T.
pyri had spread at least as far as three trees up-
and down-row from the tree in which it was re-
leased in 1997, particularly so in blocks of small
(high density) trees where intra-row tree foliage
was rather contiguous. Spread to third rows on
either side of the row in which T. pyri were re-
leased in 1997 was only slight in blocks of small
trees and essentially nil in blocks of medium-size
and large trees in 1998.

Fruit Notes, Volume 64 (Number 1), Winter, 1999

Tabic 1. Mean numbers of I . I>yn and lluropean red mites (ERM) per leaf m late Aiif;iisi and pesticides
used in third-level IPM blocks in ei^;lii commercial apple orchards in Massachusetts m ]'-)^)H where T.
pyri were released in May of 1997.

Mean n(j. per leaf

^- py'

Orchard

1997 1998

ERM
1998

Miticide used

No. EBDC"

fungicide
applications

1997

1998

1997

1998

No.

insecticide* ' '

applications

1997

1998

1.02
0.92
0.08
0.67
1.09
0.03
1.41
0.38

1.93
1.74
1.03
0.41
0.33
0.16
0.13
0.09

0.03
3.92
0.09
0.05
0.00
0.31
0.01
0.03

Oil

Savey

Agri-Mek

Savey
Pyramite

Oil
Savey

Oil
Agri-Mek
Agri-Mek
Pyramite
Agri-Mek
Agri-Mek

Averaged across all three sizes of trees sampled.

Application through mid-June, none thereafter.

Includes only insecticides known to be moderately or very harmful to T. pyri: synthetic

pyrethroids, oxamyl, methomyl and chlorpyrifos.

* » *

We are encouraged by these findings and plan Acknowledgments
to continue our study of the extent of establish-
ment and spread of T. pyri in these same third-
level IPM blocks in 1999. At the same time, we
find it sobering that the rate of spread of T. pyri
into non-release trees is apparently quite modest
and that certain pesticides that were believed to be
no more than moderately harmful to T. pyri (e.g.
Agri-Mek) may in fact be very harmful.

We are grateful to the eight growers partici-
pating in this experiment and who made special
effort to apply pesticide selectively to third-level
IPM blocks: Bill Broderick, Dave Chandler, Dana
Clark, Dave Shearer, Joe Sincuk, Tim Smith, and
Mo Tougas. This work was supported by State/
Federal IPM funds.

kK k9^ k9^ Kf^ %t^

^c ^c ^c ^c ^c

Fruit Notes, Volume 6A (Number 1), Winter, 1999

Budagovsky 9: A Summary of Fifteen
Years of Trial

Wesley R. Autio

Department of Plant & Soil Sciences, University of Massachusetts

New rootstocks are becoming available every
year, some frorn breeding programs in the United
States and others from a wide range of different
countries. Before commercial plantings of these
rootstocks begin, it is necessary to conduct trials to
understand all of the potential values of and
problems with these rootstocks. Mark is an
example of a rootstock that was planted widely
before adequate testing had occurred. It was first
planted in a large-scale test only six years before
widespread commercial planting began. Problems
with Mark started to appear in research trials just
a few years later, after many trees were already in
the ground. Hindsight suggests that waiting a few
more years would have been prudent, but the
release and promotion of new rootstocks before
we truly understand them likely will continue to
occur.

Significant quantities of data have been
collected on rootstocks that were released or
brought into the U.S. in the 1970's and 1980's.
This collection of rootstocks, not those that are
just being released, should form the list of
alternatives to the well known Mailing and
Malling-Merton series. A few of these rootstocks
will be discussed in upcoming issues of Fruit
Notes. In this issue, Budagovsky 9 is the focus.

In 1974, Jim Cummins and Dick Norton
described Budagovsky 9 (B.9) as "the most
promising candidate to replace M.9." B.9 was
released from the Michurin College of Horticul-
ture in central Russia, having been selected from a
cross of M.8 and 'Red Standard.' In many
respects, it was considered very similar to M.9;
however, it was more cold hardy and more
resistant to collar rot (Ferree, D.C. and R.F.
Carlson. 1987. Apple rootstocks. In: Rootstocks
for Fruit Crops. John Wiley &: Son, New York).

In Massachusetts, the first planting including
B.9 was part of an NC-140-coordinated trial

established in 1984. This trial included 15
rootstocks with Starkspur Supreme Delicious as
the scion cultivar. Since then, additional trials
including B.9 were established in 1990, 1994,
1995, and 1997 with Marshall Mcintosh, Golden
Delicious, Jonagold, Empire, Rome, Gala,
Cortland, Rogers Mcintosh, Pioneer Mac, Ginger
Gold, Fortune, and Honeycrisp as scion cultivars.
This article will provide data from all but the most
recent plantings, extracting data from each
experiment to compare B.9 with M.9 and/or
M.26. These data are given in Table 1.

In general B.9 produced a tree similar in size to
M.9, possibly slightly smaller than those on M.9
EMLA and slightly larger than those on M.9 (dirty
9). The trunk cross-sectional area of trees on B.9
was on average 50% (40 and 75% range) of that of
trees on M.26.

Rootstock did not affect yield per tree
significantly. Efficiency, however, was dramati-
cally affected by rootstock. M.9 and B.9 resulted
in similar efficiency, but they were about 50%
more efficient than trees on M.26. The practical
result of this difference in efficiency is that trees on
M.9 or B.9 will yield more per acre than those on
M.26.

B.9, M.9, and M.26 all resulted in good fruit
size, and there were no consistent differences
among the three rootstocks. Overall, average fruit
size in these studies averaged about 200 g {96
count), attesting to the fact that these dwarfing
rootstocks regularly result in large fruit, even with
a lack of irrigation, as was the case in all of the
trials.

Other data not shown here suggested that B.9
results in a similar timing of fruit ripening and
similar fruit quality to those from trees on M.9.

In conclusion, 15 years of study show B.9 to be
a good apple rootstock. Performance in
Massachusetts, however, does not suggest that B.9

Fruit Notes, Volume 64 (Number 1), Winter, 1999

I .ibic 1. (,hnr.ictcnsiics ot trees ot v.inous cultivars on B.9 m comparison to M.9 and M.26. These d.ita
were extracted (roni several replicated trials, and in most cases, represent conditions through the end of
the 1998 growing se.ison (Delicious data, however, were collected through the end of the 1 993 season).
fTiiit size IS the aver.ige over all triiiting \ears (or each trial.

Cumulative

Trunk

yield

Fruit

Tree

cross-

Cumulative

efficiency

size

age

sectional

yield per

(Ibs/in'

(no./42-

(years)

Cultivar

Rootstock

area (in^)

tree (bu)

TCA)

Ib box)

Delicious

B.9

3.9

7.3

M.26 EMLA

6.4

9.1

Marshall Mcintosh

M.9 EMLA

5.6

6.1

112

B.9

4.0

5.4

111

M.26 EMLA

10.9

6.3

127

Golden Delicious

M.9 EMLA

5.7

5.1

101

B.9

5.7

5.4

M.26 EMLA

7.4

5.8

Jonagold

M.9 EMLA

5.6

6.3

B.9

6.4

M.26 EMLA

11.8

7.8

Empire

M.9 EMLA

5.1

7.1

101

B.9

4.5

5.6

103

M.26 EMLA

9.5

5.2

106

Rome

M.9 EMLA

8.5

9.8

B.9

5.4

7.4

M.26 EMLA

8.8

8.6

Gala

M.9 EMLA

3.9

1.8

110

B.9

2.9

1.7

120

M.26 EMLA

5.9

1.9

120

Cortland

M.9

1.2

0.2

B.9

1.4

0.4

Rogers Mcintosh

M.9

1.6

0.3

101

B.9

1.7

0.2

121

Pioneer Mac

M.9

1.1

0.3

108

B.9

1.7

0.2

127

Ginger Gold

M.9T337

1.1

0.3

B.9

1.1

0.3

is a better rootstock than M.9. However, northern a problem, growers may see better performance
apple-growing regions where winter damage may from B.9 than M.9.
be a problem and in blocks where collar rot may be

Fruit Notes, Volume 64 (Number 1), Winter, 1999

Kites

Fruit Notes

University of Massachusetts

Department of Plant & Soil Sciences

205 Bowditch Hall

Amherst, MA 01003

Nonprofit Organization
U.S. Postage Paid

Permit No. 2
Amherst, MA 01002

SERIAL SECTION

UNIV OF MASSACHUSETTS LIBRARY

AMHERST MA 01003

Account No. 2-22914

Volume 64, Number 2
SPRING ISSUE, 1999

Table of Contents

Characteristics of Scald Susceptibility and Development on Cortland Apples in New England

Effects of Planting Density and IPM Level on Apple Fruit Quality
Evaluation of Flint and Sovran, Two New Strobilurine Fungicides, Against Apple Diseases

Ottawa 3: A Summary of Twenty Years of Trial

Editors:

Wesley R. Autio
William J. Bramlage

Publication Information:

Fruit Notes (ISSN 0427-6906) is pub-
lished the each January, April, July, and
October by the University of Massachu-
setts in cooperation with the other New
England state universities.

Correspondence should be sent to:

Fruit Notes

Department of Plant & Soil Sciences
205 Bowditch Hall
University of Massachusetts
Amherst, MA 01003

All chemical uses suggested in this publication are contingent upon continued registration.
These chemicals should be used in accordance with federal and state laws and regulations.
Growers are urged to be familiar with all current state regulations. Where trade names are
used for identification, no company endorsement or product discrimination is intended. The
University of Massachusetts makes no warranty or guarantee of any kind, expressed or
implied, concerning the use of these products. USER ASSUMES ALL RISKS FOR PERSONAL
INJURY OR PROPERTY DAMAGE.

Issued by UMass Extension, John Gerber, Director, in furtherance of the acts of May 8 and June 30, 1914.
UMass Extension offers equal opportunity in programs and employment.

Characteristics of Scaid Susceptibility
and Development on Cortland Apples
in New England

Sarah A. Weis, William J. Bramlage, and William J. Lord
Department of Plant & Soil Sciences, University of Massachusetts

Postharvest development of scald is a severe threat
for certain cultivars of apples. Cortland is particularly
susceptible, so much so that growers would likely have
discontinued production except for the discovery that
scald could be controlled by treatment with
diphenylamine (DPA). Even today, however,
Cortland fruit stored long-term carry a significant risk
of scald development.

In the Spring 1998 issue of FruitNotes, we
reported on the success we have had in predicting scald

susceptibility of New England Delicious apples, using
equations based on harvest date, preharvest tempera-
ture, and harvest starch score of the fruit. At the same
time that we have been studying scald prediction for
Delicious, we have also been attempting to develop a
similar prediction system for Cortland. For reasons we
are unable to explain, we have failed in these efforts
with Cortland. However, during our experiments we
have learned much about scald development on this
cultivar, and here we report some of these findings that

H] On removal from storage ■ Following 7 days at 68 F

Figure 1 . Scald development following 20 weeks of 32^ air storage of Cortland apples (harvest dates vary).

Fruit Notes, Volume 64 (Number 2), Spring, 1999

nOn removal from storage ■ Following 7 days at 68 F

Figure

2. Scald development following 25 weeks of 32°F air storage of Delicious apples (harvest dates vary).

lead us to a set of conclusions about the current state of
knowledge regarding scald development and control
for New England-grown Cortland apples.

In our studies, we collected Cortland apples from
1985 through 1998 at the Horticultural Research
Center (HRC), Belchertown, MA. In addition,
samples were collected from other sites: Shelbume
and Warren, MA (1997), Putney, VT (1996), Durham,
NH (1995, 1996, and 1997), Storrs, CT (1995), and
Monmouth, ME (1996). Each sampling site provided
at least two harvests per year indicated. Fruit were
stored at 32"F in air for 20 weeks, and then kept at 68"F
for one week, after which scald development was
evaluated. (In some years, scald was evaluated both at
removal from storage and again after one week at
68°F.) All fruit were standard Cortland, i.e. no red
sports were used. Fruit were not treated with DP A.

Cortland and Delicious differ in a very important
way in the manner in which they develop scald. Figure
1 shows the presence of scald immediately upon
removal from storage and then again after one week at
room temperature. In most cases, little or no scald was

present when the Cortlands were removed from
storage, but it was present, sometimes extensively,
after the fruit had been warmed. In contrast. Figure 2
illustrates the performance of Delicious. On these
fruit, most scald was present at removal from storage,
with only slight increases at room temperature. This
means that Cortlands are very deceptive. They may
look scald-free at the time of packing but become
badly scalded once they warm up. Delicious, on the
other hand, do not present this problem. A trip to the
supermarket can be instructive. Rarely will you find a
scalded Delicious on display, but scalded Cortlands
are a common occurrence. Scalded Delicious usually
can be removed during packing, but many Cortlands
scald after packing.

For a scald prediction system to be of value, you
must have considerable variation in scald development
on samples. You can see in Figure 1 that this was the
case in our experiments. Some samples developed
hardly any scald while others developed a great deal of
it. What are the sources of scald variation in Cortland?

In Figure 3 you see year-to-year variation in scald

Fruit Notes, Volume 64 (Number 2), Spring, 1999

1985 1986 1987 1988 1989 1990 1991 1992 1993 1995 1996 1997 1998

Harvest year

Figure 3. Year-to-year variation in mean scald development on HRC-grown Cortland apples (means corrected to
account for differences in harvest dates each year).

susceptibility of Cortland apples from the HRC in
Belchertown, MA. Scald always occurred, but it was
much worse in some years (e.g. 1985 and 1993) than in
others (e.g. 1988 and 1997). Thus, some years were
"bad scald years" while others were not, although no
year was scald-free.

In Figure 4, you see orchard-to-orchard variation
in Cortland scald development in New England. No
particular pattern is evident, except that 1997 seems to
have produced less scald than 1995 or 1996. Even this
difference may be confounded by the fact that the 1997
samples were harvested on average 3 days later than
the 1996 samples, but with an average starch score of
3.6 in 1997 vs 3.8 in 1996 (i.e. fruit were harvested
slightly later, but slightly less ripe in 1997) . That the
fruit from Monmouth, ME did not develop more scald
than they did seems remarkable, since those samples
were exposed to less cool weather (8 days of sub50"F
before harvest for ME vs overall mean of 1 7 days) than
were any other group of samples, had the lowest starch
scores (ME mean of 2.5 vs overall mean of 3.9 ), and
were among the earliest harvested (ME mean of
September 27 vs. overall mean of October 3). All
those factors generally are considered "scald
enhancing."

Time of harvest is a major factor in scald
susceptibility of apples, and it is certainly a factor for

Cortland. Figure 5 presents a composite of scald
development on all of our samples, across years and
sites, based on harvest date of the fruit. Cortlands
picked before September 21 were extremely scald
susceptible, while those picked after October 20
developed almost no scald, regardless of year or
growing site. Between these extremes, susceptibility
gradually fell as harvest date was later. However,
delaying harvest until fruit have low susceptibility
clearly is not desirable. Not only do they become
excessively soft, but they also become susceptible to
senescent breakdown, which occurred in 30% of fruit
harvested after October 15.

Since there is so much variation in Cortland scald
susceptibility, an effective method of predicting
poststorage scald development at the time of harvest
could be very useful in guiding strategies to control
scald, e.g. whether or not to apply DPA, and , if so,
what concentration to use. However, none of the
equations we have created to relate preharvest
conditions, such as we described for Delicious in the
Spring 1998 issue of FruitNotes, have given reliable
results in separating lots of fruit by their relative scald
susceptibility. In Figure 6 are presented 10 years of
results from the HRC, comparing percent scald
"predicted" (in hindsight) from harvest date, starch
score, and number of preharvest sub 50"F days to

Fruit Notes, Volume 64 (Number 2), Spring, 1999

,0p ,0|-

Figure 4. Orchard-to-orchard variation in scald susceptibility of Cortland apples in 1995, 1996, and 1997.

^"^

^^ / / / v-^" / v-^" v-^"

:- -V ,»te ^\V aJ^ vA u> v^

^^ cfvv ^^

Harvest Date

Figure 5. Effect of harvest date on poststorage scald development on NE-grown Cortland apples; 506 samples,
1985-98.

Fruit Notes, Volume 64 (Number 2), Spring, 1999

inn --

lUU

^ r. „

n=> 80 -

1 60
S 40 -
^ 20 '

O, 1

n 1

■

■ - ■■ 1

■ 1

■ ■
■

■ 1 ■

,- -".

■■ . .

!+■ — m^

■ ■ ■ ■■

■

■ ■ i

■ J
1 L ^^r

i-ir ■-

■ ■ • *

■ ■

■

„ m ■ 11.

■■ ■ ■

u * - — 1 1 1 1 ■ 1

20 40 60 80 100

percent scald observed

% scald = 116.8 - 1.43*(harvest date where 9/1 = 1)- 1.20*(n of preharvest days<50) - 1 .58 *(harvest starch)

Figure 6. HRC generated equation showing predicted vs. actual scald on HRC Cortland apples 1988-1997.

actual percent scald observed. While the trend of the
data seems encouraging, the reliability of the
predictions is not acceptable. Furthermore, this
equation gave much worse results when applied to
fruit harvested from other orchards in new England.
We are continuing to pursue an effective predictive
system, but as of now, we have not produced a tool in
which we have confidence.

Based on nearly 15 years of experiments with
Cortland, we draw the following conclusions about
scald susceptibility of this cultivar in New England:

1 . Scald susceptibility varies enormously from site to
site, and also from year to year within a site.
Because your fruit did or did not scald last year is
not a reliable index of what they will do this year.

2. Susceptibility declines as fruit mature and, to
some extent, as they experience increasing
exposure to temperature below 50"F before
harvest. However, delaying harvest to obtain
scald resistance can result in soft fruit that develop
senescent breakdown.

3. We still cannot predict scald development on
Cortland.

4. At this time DPA is the only reliable method of

controlling scald on Cortland. Unlike with
Delicious, we have not been able to predict the
concentrations needed to control Cortland scald.
5 . Because Cortlands are scald-free at removal from
storage does not mean they will remain scald-free
when they warm to room temperature. Most scald
symptoms develop after storage of this cultivar.
Effective scald control treatment at harvest time is
your best assurance that Cortlands will remain
scald-free during their shelf life.

We wish to express sincere thanks to the following
people who contributed greatly to this work by
providing samples of fruit for study: Mr. Joseph
Sincuk, HRC, Belchertown, MA, Mr. Dana Clark,
Clark Orchards, Ashfield, MA, Mr. Evan Darrow,
Green Mountain Orchards, Putney, VT, Mr. Timothy
Smith, Apex Orchards, Shelbume, MA, Mr. Mark
Tuttle & Mr. Robert Tuttle, Breezelands Orchards,
Warren, MA, Professor William G. Lord, University
of New Hampshire, Dr. James Schupp, University of
Maine (now at Cornell University's Hudson Valley
Laboratory), and Dr. David Kollas, University of
Connecticut. Without their help this study could not
have been done.

Fruit Notes, Volume 64 (Number 2), Spring, 1999

Effects of Planting Density and IPI\/I Level
on Apple Fruit Quality

Arthur l\ittle, Deirdre Smith, James Hall, Michael Frank, and Daniel Cooley
Department of Microbiology, University of Massachusetts

Starker Wright, Jon Black, and Stephen Lavalle
Department of Entomology, University of Massachusetts

Wesley Autio

Department of Plant and Soil Science, University of Massachusetts

Many New England apple growers have replanted
their orchards with dwarf at densities of 400 to 1000
trees per acre. At the same time, growers have been
advancing their efforts to reduce pesticide inputs on
their land by employing bio-intensive IPM methods to
manage flyspeck disease, plum curculio, pest mites,
and apple maggot fly, which together account for al-
most all pesticide use from about June 10 to harvest.
The tree fruit research and extension team at
the University of Massachusetts and eight
growers have been integrating these horticul-
tural and pest-management practices for the
last 2 years.

Just before commercial harvest in 1997,
100 fruit were examined from each of the 48
blocks for symptoms of disease and arthro-
pod damage. As in other experiments of this
3-year study, there were six blocks per orchard
and eight orchards. At each orchard there
were two high-density blocks, two medium-
density blocks, and two low-density blocks.
Half of the blocks were managed according
to third-level IPM strategies, and half were
managed with traditional first-level IPM.
The blocks were Mcintosh, with an occasional
row of Cortland or similar cultivar, and were
seven rows by seven trees or as close to this
as possible. The feat of selecting and map-
ping the 48 blocks in eight orchards across
the state was considerable and could not have
been done without a very supportive and pro-
active grower community.

A sub-sample of 20 fruit were selected

from each group of 100 for fruit quality evaluations.
The 20 were weighed. The percent red color was de-
termined. Firmness was assessed with an Effigi pen-
etrometer, and juice was collected from this process.
The percent soluble solids was assessed in the juice
with a hand refractometer.

Fruit quality was not affected in 1997 by planting
density or IPM level. We hoped that fruit produced

Table 1. Fruit quality (1997) and crop density (1998) of
apples from blocks of different planting densities and IPM
levels in eight Massachusetts orchards.*

Fruit

Soluble

Red

weight

solids

color

Firmness

Treatment

(S)

(%)

(lbs.)

Planting density

Low

145 a

10.6 a

60 a

18.0 a

Medium

135 a

10.4 a

66 a

18.9 a

High

135 a

10.4 a

67 a

18.5 a

IPM level

First

139 a

10.4 a

63 a

18.5 a

Third

139 a

10.5 a

66 a

18.7 a

* Means within column and Ueatment type not followed
by the same letter are significantly different at odds of 19
to 1.

Fruit Notes, Volume 64 (Number 2), Spring, 1999

under bio-intensive "third-level IPM" would be as
colorful, sweet, large, firm, and as plentiful as fruit
produced with more chemically based IPM practices,
and this is what we found. We were surprised, how-
ever, that there were no differences due to planting
density, because other studies have shown high den-

sity apple blocks produced larger, more colorful and
more plentiful (yield per acre) fruit than blocks with
larger less densely planted trees. For 1999, we plan to
study these factors more comprehensively. We will
increase the number of apples, branches, and trees that
are examined.

•s!^ *^ •st* •st^ •J^

•^ •^ ¥^ •^ ^^

Evaluation of Flint and Sorvran,Two New
Strobilurine Fungicides, Against Apple
Diseases

Daniel Cooley and Arthur 1\ittle

Department of Microbiology, University of Massachusetts

Joe Sincuk

Department of Plant & Soil Sciences, University of Massachusetts

Heather Faubert

Department of Plant Sciences, University of Rhode Island

For the first time in many years, the agricultural
chemical industry is releasing new types of fungicides
for control of apple diseases. One new class of fungi-
cides, the strobilurines, is particularly interesting. The
first registered versions of these on apples are Flint®
(trifloxystrobin) and Sovran® (kresoxim-methyl). The
original discovery of this class of chemistry was in a
forest mushroom, Strobilurus tenacelius. In a natural
setting, the mushroom produces a chemical called
strobilurine to fight off other fungi that may be trying
to feed off the forest debris, or off the mushroom it-
self. Strobilurine A is a natural fungicide. Several com-
panies have synthesized versions of chemicals similar
to Strobilurine A, collectively called strobilurines, and
are completing evaluation and registration of them.

These fungicides offer some interesting opportu-
nities for apple growers. They are very effective against
scab and fly speck, the two key fungal diseases of apple

in New England. In addition, they have a very clean
bill of health on the environmental front, with low tox-
icity to mammals, bees, birds, and earthworms. While
toxic to fish and other aquatic organisms, strobilurines
are broken down very quickly, and tests show that un-
der normal use patterns, they will not reach water be-
fore they break down.

It will also be important to use them wisely, since
it will be relatively easy for pathogens to develop re-
sistance to them. Indications are that the resistance
that develops will be "all or nothing." That is, if resis-
tance develops, it will come on with little warning,
probably leaving significant disease in the wake.

The manufacturers recognize the potential for re-
sistance and attempted to address the problem by lim-
iting the total number of applications that can be made
in a year, the amount of material that may be applied
in a year, and the number of consecutive sprays of

Fruit Notes, Volume 64 (Number 2), Spring, 1999

strobilurines that may be applied. There are differ-
ences between the two labels in these respects. The
Flint label uses a more cautious approach. For Sovran,
the manufacturer "recommends" no more than three
applications in a row. The Flint label states "use a
maximum of two consecutive applications." The
Sovran label says "do not make more than six applica-
tions per season". The Flint label carries a five appli-
cation limit. The Sovran label states that Sovran should
not be used as the last fungicide application of the sea-
son, while Flint does not have that restriction on the
label.

At the very least, the label recommendations and
limits should be followed strictly. A conservative ap-
proach would be a four application per season limit,
with a maximum of two consecutive applications. All
strobilurins have the same mode of action, so the limit
of four applications per season would apply to the to-
tal number of Sovran and Flint sprays. Because
strobilurines work well on fruit scab and other diseases,
there is no compelling reason to tank-mix them with a

broad-spectrum protectant as there is with the sterol
inhibitor fungicides. Rather, the manufacturers have
chosen to recommend alternating pairs of applications.
Pairs of applications made 7 to 10 days apart sounds
similar to the "back-to-back" applications recom-
mended for the SI fungicides such as Rubigan and
Nova. However, the important point with the
strobilurines is to use a different class of fungicide af-
ter making two strobilurine applications in order to
reduce the chances that resistance will develop. There
certainly are a number of unanswered questions about
the best way to manage resistance, but that probably
argues for taking a relatively cautious approach to us-
ing the strobilurines.

Both products exhibit excellent post-infection ef-
ficacy, similar to the 4-day activity of the SI fungi-
cides. As you might expect with this sort of post-in-
fection efficacy, the strobilurines are somewhat sys-
temic. The strobilurines show some protectant activ-
ity, probably on the order of 3 to 6 days. Therefore,
recommended intervals between applications are 7 to

Table 1 . Effects of sterol inhibitors, mancozeb, and a cyprodinil/trifloxystrobin treatment on the incidence of

scab in mature Mcintosh,

Belchertown, MA, 1998

Primary scab season

Summer fungicides

Scab incidence (%)

Fruit

fungicides (per 100 gal.)

(per 100 gal.)

Terminals

Clusters

Fruit

(harvest)

Nova 40W+ Dithane

Captan SOW (1 lb.)

0.4 c

0.0 c

0.6 b

1.8 b

75DF (1.7oz.-hllb.)

Rubigan 1 .6 EC+ Dithane Captan SOW (1 lb.)

1.1c

0.8 c

1.2 b

1.6 b

75DF (2.7 oz. + I lb.)

Dithane 75DF (lib.)

Captan SOW (1 lb.)

14.0 b

11.7b

2.5 b

1.0 b

Vangard 75WG [pink.

Flint SOWG+ CapUn

2.0 c

0.4 c

1.2 b

3.2 b

bloom]; Flint 50WG

(2.2S oz. + 1 lb.)

[petal fall, lstcov.](1.7

oz.; 0.75 oz.)

UnU-eated control

S7.0a

59.9 a

23.7 a

50.0 a

* Means within columns

not followed by the same

letter are significantly different at odds of 19 to 1

Fruit Notes, Volume 64 (Number 2), Spring, 1999

Table 2. Effects of cyprodonil and

U-ifloxystrobin on incidence of scab in mature Mcintosh,

Belchertown, MA , 1999.

Primary scab season fungicides

Summer fungicides

Scab incidence (%)

Fruit

(per 100 gal.)

Terminals

Clusters

Fruit

(harvest)

Vangard 75WG ( 1 .7 oz.) 2

Flint 50 WG (0.7 oz.)

applications; then Vangard 75WG

10 days after pf; 14-21

(1.7oz.)plusDithane75 DF(1

days

lb.) through petal fall

Vangard 75WG (1.7 oz.) 2

Flint 50 WG (0.7 oz.)

5 be

1 b

applications; then Vangard 75WG

21 days after pf; 21 -28

(1.7 oz.) plus Dithane 75 DF (1 lb)

days

through petal fall

Flint 50 WG (0.7 oz.)

Captan50W(llb.)

Untreated control

31 a

20 a

* Means within columns not followed by the same letter are significantly different at odds of 19 to 1.

10 days.

We have tested Flint for the last two years in scab
trials, and looked at Sovran in a flyspeck trial this past
year. In addition, several other researchers have run
tests of one or both of these fungicides in recent years.
We show some of the results of our trials here. The
scab trials were done at the Horticultural Research
Center in Belchertown, with an airblast sprayer. The
fungicides were applied on schedules that would nor-
mally be used in a growers orchard. However, the
manufacturer of Flint wanted to include another new
fungicide, Vangard (cyprodonil) in the tests. Vangard
represents another new class of fungicide chemistry,
but appears to be of limited value to apple growers.

In Table 1 includes 1998 results. It shows that the
Flint treatment performed as well as standard Rubigan
or Nova plus Dithane treatments against fruit and fo-
liar scab. While the percentages were slightly differ-
ent, the differences were not significant. By compari-
son, a low rate of Dithane (1 lb. / 100 gal.) did a rela-
tively poor job of controlling early foliar scab. How-

ever, by the end of the summer, following three appli-
cations of captan on all treatments, fruit in the Dithane
treatment were comparable to those in the other fungi-
cide treatments.

In the 1998 test (Table 2), Vangard performed well
when used in combination with the strobilurine. How-
ever, the 1999 test suggested that Vangard may not be
carrying much of the load in RintA'angard combina-
tions. While the differences generally were not sig-
nificant, there was no scab where Flint was used alone,
but 4 to 5 % foliar scab in treatments where Vangard
was used in the early season. Scab on fruit at harvest
was similar. While this test is not conclusive, data
from the Hudson Valley Lab (Rosenbergeret al., 1998)
showed clearly that Vangard did not control scab as
well as Flint when both were used on a 10-day spray
interval during the exceptionally wet 1998 season.
(Table 3).

Tests for flyspeck control in Belchertown have
been less conclusive. This year, the dry weather and
the low inoculum in Belchertown made it unlikely that

Fruit Notes, Volume 64 (Number 2), Spring, 1999

Table 3. Effects of cyprodonil and trifloxystrobin on incidence of scab in mature Jerseymac, Highland
(Adapted from Rosenberger et al., 1998).

, NY, 1998

Scab Incidence (%)

Fungicide (per 100 gal.) Terminals

Clusters

Fruit
(harvest)

Vangard 75WG (1.68 oz. ) 2 applications; then Flint 50 WG (0.75 oz.) 3.2 b
2 applications; then Flint 50 WG (0.75 oz.) plus Captan 50W (12 oz.).

Flint 50 WG (0.75 oz.) 0.1c

Flint 50 WG (0.5 oz.) 0.6 c

Untreated control 67.5 a

30.1 b

2.0 c

3.4 c

97.5 a

54.3 b

19.2 c
26.6 be
100.0 a

* Means within columns not followed by the same letter are significantly different at odds of 19 to 1.

we would get flyspeck. Therefore, we did a single-
application test in a block of Liberty trees at the Uni-
versity of Rhode Island East Farm in Kingston. By the
time the application was made on July 29, flyspeck
was already evident in the test block. Test trees re-
ceived no fungicides for the season except for the ap-
plication that was part of this test. Flint and Sovran
were compared to Benlate plus captan and to calcium
chloride. The results are shown in Table 4 and Figure
1.

Strobilurines
performed as well as
or better than the
best standard treat-
ment, Benlate plus
Captan, in a single
application. The dif-
ference between
Flint and Sovran
may be due to a rate
effect, as it has been
suggested that
Sovran should be
used at twice the
Flint rate for equiva-
lent activity. The

single application of calcium chloride did not signifi-
cantly reduce flyspeck at harvest, but did appear to
slow the epidemic. It also appears that the effect of
the strobilurines lasted for approximately 3 weeks, at
which point the rate of flyspeck-symptom appearance
in both strobilurine treatments and the Benlate/captan
treatment were similar. The early effect meant that at
harvest, Flint was still significantly better than Benlate/
captan in terms of flyspeck control.

Table 4. Flyspeck severity in apples treated with a single fungicide application on
July 29, 1999, Kingston, RI.

Treatment

Flyspeck*

Check 2.73 a

Calcium chloride 80% 10 lbs. / acre 2.46 a

Benlate 50 WP 9 oz. / acre plus captan 50W 3 lbs. / acre 1 .64 b

Sovran 3.2 oz. /acre 1.41 be

Flint 2 oz. /acre 1.14 c

♦Rating for each fruit: O^clean; 1=<10%; 2=10-40%; 3=>40%,
followed by the same letter are significantly different at odds of 19 to 1.

Means not

Fruit Notes, Volume 64 (Number 2), Spring, 1999

120%

100%

o 80%

<1*

■c

— 60%

a»
o.
en

^ 40%

20%

—

Check

Caldum

Ben/Cap

---A--

_.«

--X--

Sovran
Rint

/»

y
y

.-' y'

y''

/ j^
/ /'

,-' ^y

' ^ y'

-->

,y'

^ . -^ ;^

:'---*•

,,-o^r''

^y '

7/28/99 8/4/99 8/11/99 8/18/99 8/25/99 9/1/99 9/8/99 9/15/99 9/22/99 9/29/99

Date

Figure 1 . Percentages of fruit showing flyspeck symptoms following sprays with calcium chloride
and three different fungicide treatments, Kingston, RI, 1999.

The strobilurines may represent a real opportunity
to improve our summer-disease managment. So far,
no interactions with mite management have appeared.
Residue problems with the strobilurines, as compared
to Benlate or captan, might be expected to be minimal.
Rather than focusing the strobilurines on scab, it might
be useful to reserve at least a couple of applications
for flyspeck.

So, should Flint or Sovran be purchased for the
2000 growing season? Both materials have performed
very well against scab and flyspeck, so the limiting
factor will probably be price. The chemical compa-
nies are aware of this, and will probably price the
strobilurines to be competitive with the combined cost
of an SI plus protectant. Captan or mancozeb alone
probably will be cheaper. If price is an issue and grow-
ers cut strobilurine rates below the label minimums,
then control may not be very good, especially without
a protectant to act as a back-up.

Strobilurines are good antisporulants. That is, they
prevent active scab from producing large numbers of

viable conidia that can cause more infections. They
will do a good job stopping or slowing an epidemic.
However, more than 96 hrs after the start of an infec-
tion, it is unlikely that strobilurines will stop symptom
development. With the SI fungicides, applications a
few days beyond the 96-hour post-infection recommen-
dation would usually stop symptom development, or
limit it to yellow spotting. This will probably not be
the case with the strobilurines. In addition, post-in-
fection use will hurry the process to resistance devel-
opment.

Another factor to consider is what might be called
"new product caution." With any new product, un-
foreseen circumstances may yield unexpected perfor-
mance problems. While the strobilurines look great, it
might be prudent to use them on a limited basis for a
year or two. A lot will be learned about the strobilurines
as commercial growers begin to use them. In short,
use them where the price and timing fits your needs,
but do not abuse them by cutting rates, or applying
extra applications.

Fruit Notes, Volume dA (Number 2), Spring, 1999

Ottawa 3: A Summary of Twenty
Years of Trial

Wesley R. Autio

Department of Plant & Soil Sciences, University of Massachusetts

This article is the second in a series summarizing
the data collected in Massachusetts on specific apple
rootstocks over a number of years. Ottawa 3 (0.3) is
the focus of this installment. The Ottawa series of
rootstocks dates back to the 1950's and 1960's. They
were selected at the Ottawa Research Station. 0.3
resulted from a cross of Robin (a hardy crab apple) and

M.9. It is more resistant to collar rot than M.26 and
somewhat less resistant than M.9. It is sensitive to
fireblight. Propagation has been a problem, but Traas
Nurseries in Canada have been relatively successful
with tissue culturing of 0.3, providing most rootstock
liners for nurseries producing finished trees on 0.3.
In Massachusetts, the first planting including 0.3

Table 1 . Characteristics of trees of various cultivars on 0.3 in comparison to M.9 and M.26. These data were
exuacted from several replicated trials, and represent conditions through the end of the 1999 growing season for
Golden Delicious, Empire, Rome, and Gala, through 1994 for Mcintosh, and through 1993 for Delicious. Fruit
size is the average over all fruiting years for each trial.

Tree

age

(years) Cultivar

Rootstock

Trunk

cross-
sectional
area (in^)

Cumulative
yield per
tree (bu)

Cumulative

yield

efficiency

(lbs/in'

TCA)

Fruit size
(no./42-
Ib box)

Delicious

Mcintosh

Golden Delicious

Empire

Rome

Gala

M.26 EMLA
M.9 EMLA
0.3

M.26 EMLA
0.3

M.26 EMLA
M.9 EMLA
0.3

12.7
5.2
8.8

10.2
6.9

8.4
6.5
8.0

10.9
4.9

7.3

27
18
23

13
13

9
8
12

94
143
110

57
77

45
48
62

34
80
63

91
86
88

115
115

97
101
95

108
99
102

M.26 EMLA

9.7

M.9 EMLA

9.6

0.3

8.9

M.26 EMLA

7.0

107

M.9 EMLA

5.0

102

0.3

4.5

110

Fruit Notes, Volume 64 (Number 2), Spring, 1999

was part of an NC-140-coordinated trial established in
1980. This trial included 9 rootstocks with Starkspur
Supreme Delicious as the scion cultivar. Since then,
additional trials including 0.3 were established in
1985, 1990, and 1994 with Summerland Red
Mcintosh, Smoothee Golden Delicious, Nicobel
Jonagold, Empire, and Law Rome as scion cultivars.
This article will provide information from all of these
plantings, extracting data from each experiment to
compare 0.3 with M.9 and/or M.26. These data are
given in Table 1 .

In general, 0.3 produced a tree that was
intermediate to those on M.9 EMLA and M.26 EMLA
rootstocks. Exceptions include scions Rome and Gala,
where trees on 0.3 were similar in size to those on M.9
EMLA.

Relative to M.26, 0.3 yielded somewhat less per
tree with Delicious and Mcintosh, somewhat more
with Golden Delicious and Empire, and similar to
M.26 with Rome and Gala. With the exception of
Rome, trees on 0.3 generally yielded more than those
on M.9. In all cases, trees on 0.3 were more yield
efficient than those on M.26 EMLA. They also were
more efficient than trees on M.9 with Gala and Golden
Delicious as scions. The practical result of these

differences is that 0.3 will generally produce a tree
that is between M.26 and 0.3 in size but will yield
more per acre, when appropriately spaced in the field,
than trees on M.26.

0.3, M.9, and M.26 all resulted in good fruit size,
and there were no consistent differences among the
three rootstocks. Overall, average fruit size in these
studies averaged about 200 g (96 count), attesting to
the fact that these dwarfing rootstocks regularly result
in large fruit, even with a lack of irrigation, as was the
case in all of the trials.

0.3 was compared with eight other rootstocks
(including M.9 EMLA and M.26 EMLA) at 27 sites
throughout the U.S. and Canada as part of a
cooperative NC-140 trial. After 10 years, trees on 0.3
were intermediate in size and yield per tree to those on
M.9 EMLA and M.26 EMLA. Trees on 0.3 and M.9
EMLA were similarly efficient and significantly more
efficient than those on M.26 EMLA.

The data from Massachusetts and from the NC-
1 40 trial suggest that 0.3 is a good rootsock, one that is
worthy of grower trial. Some studies have grown 0.3
unsupported, but in many cases, trees on 0.3 lean at the
trunk. Therefore, some form of support likely will be
beneficial.

*X* vL* vl* *X* vl*

#Y* *y* •y* •x* *T*

Fruit Notes, Volume 64 (Number 2), Spring, 1999

Fruit Notes

University of Massachusetts
y , Department of Plant & Soil Sciences
Ml" 205 Bowditch Hall

^^^ Amherst, MA 01003

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Permit No. 2
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rlewOnqland

Volume 64, Number 3
SUBIMER ISSUE, 1999

Table of Contents

Comparison of Baited and Unbailed Traps for Monitoring Plum Curculios in Apple Orchards

Fruit Odors are More Attractive than Conspecific Odors to Aduh Plum Curculios

Several Host-odor Compounds are Attractive to Plum Curculio Adults

Evaluation of Kaolin Clay (Surround™) for Control of Plum Curculio

Food Quality Protection Act: An Update, February 2000

flewCnqland

Editors:

Wesley R. Autio
William J. Bramlage

Publication Information:

Fruit Notes (ISSN 0427-6906) is pub-
lished the each January, April, July, and
October by the University of Massachu-
setts in cooperation with the other New
England state universities.

Correspondence should be sent to:

Fruit Notes

Department of Plant & Soil Sciences
205 Bowditch Hall
University of Massachusetts
Amherst, MA 01003

All chemical uses suggested in this publication are contingent upon continued registration.
These chemicals should be used in accordance with federal and state laws and regulations.
Growers are urged to be familiar with all current state regulations. Where trade names are
used for identification, no company endorsement or product discrimination is intended. The
University of Massachusetts makes no warranty or guarantee of any kind, expressed or
implied, concerning the use of these products. USER ASSUMES ALL RISKS FOR PERSONAL
INJURY OR PROPERTY DAMAGE.

Issued by UMass Extension, John Gerber, Director, in furtherance of the acts of May 8 and June 30, 1914.
UMass Extension offers equal opportunity in programs and employment.

Comparison of Baited and Unbailed
Traps for l\/lonitoring Plum Curculios
in Apple Orchards

Ronald Prokopy, Bradley Chandler, Tracy Leskey, Starker Wright,

and Jonathan Black

Department of Entomology, University of Massachusetts

In the Summer 1998 issue of Fruit Notes, we pre-
sented two articles describing results of 1998 tests in
which we evaluated responses of plum curculio (PC)
adults to several different types of unbaited traps in
commercial and unsprayed orchards. Here, we report
on 1999 tests in which we evaluated not only unbaited
but also baited versions of the same types of traps tested
in 1998 as well as a new trap type called a circle trap.

Materials & Methods

In eight commercial orchards, we evaluated three
types of traps: (a) black pyramid traps (24 inches wide
at base x 48 inches tall) placed on the ground next to
apple tree trunks, (b) black cylinder traps (3 inches
diameter x 12 inches tall) fixed vertically onto hori-
zontal branches within apple tree canopies, and (c) alu-
minum-screen "circle" traps (developed in Oklahoma
for pecan weevils) and wrapped tightly around ascend-
ing tree limbs, designed to intercept PC adults walk-
ing upward. Traps were placed in six blocks of apple
trees in each orchard. Each block consisted of seven
perimeter trees. Each tree (save one) contained one
unbaited and one baited trap of the above types. The
bait consisted of a combination of one polyethylene
vial containing limonene and two polyethylene vials
containing ethyl isovalerate (components of host fruit
odor found to be attractive to PCs in 1998 studies) plus
one rubber septum impregnated with grandisoic acid
(attractive male-produced pheromone of PC). Vials
were attached to the exterior of traps at mid height,
and the septum was placed inside the inverted wire-
screen funnel (boll weevil trap top) that capped each
trap and captured responding PCs. All traps were de-
ployed at bloom and were examined for captured PCs
every 3 to 4 days for 6 weeks thereafter. At each trap
examination, 15 fruit on each of the seven trees per
block were examined for PC oviposition scars. All

blocks received two grower-applied sprays of
azinphosmethyl to control PC.

In three small unsprayed orchards, we evaluated
unbaited and baited pyramid and cylinder traps as well
as clear Plexiglas squares (2 feet x 2 feet) fastened
vertically 5 feet above ground to wooden poles seated
in the ground. One side of each Plexiglas square was
coated with Tangletrap to capture alighting PCs.
Plexiglas traps were positioned with sticky-side fac-
ing woods either 6 feet from the edge of woods or 1
foot outside of perimeter foliage of apple trees. Traps
were placed in four blocks of apple trees in each or-
chard. Each block consisted of six perimeter trees.
Each tree contained one unbaited and one baited trap
(above type bait) of each trap type. Each block in two
of the orchards also received one unbaited and one
baited clear Plexiglas trap placed at the edge of woods.
All traps were emplaced at bloom. Every 3 to 4 days
thereafter for 6 weeks, traps were examined for cap-
tured PCs, and fruit were examined for PC scars. No
insecticide was applied to any of the blocks.

Results

In commercial orchards, significantly more (about
three-times more) total PCs were captured by pyramid
traps than by cylinder traps, with circle traps captur-
ing no PCs (Figure 1). There was no significant dif-
ference in captures between unbaited and baited traps
of any type (Figure 1). Disappointingly, none of the
three types of baited or unbaited traps yielded captures
whose amount or phenology (pattern of occurrence over
time) reflected even in a very minimal way the amount
or phenology of egglaying injury to fruit caused by
PC. If there were a perfect relationship between trap
captures and injury, then the statistical indicator of such
a relationship (called r) would have a value of 1.00.
Here, the r value describing the relationship between

Fruit Notes, Volume 64 (Number 3), Summer, 1999

0.70

0.00

Unbailed Baited

Pyramid

Unbailed Baited

Circle

Unbailed Baited

Cylinder

Trap type

Figure 1. Captures of plum curculios on unbailed and baited pyramid, cylender, or circle traps in commercial
orchards. Bars not superscribed by the same letter are significantly different at odds of 19 to 1.

abundance of PCs in traps and amount of injury never
exceeded 0.37 for any type of unbailed or baited trap,
and the r value describing the relationship between time
of capture of PCs in traps and time of injury did not
exceed 0.24 for any type of unbailed or baited traps.

In unsprayed orchards, significantly more (about
eight times more) PCs were captured by pyramid traps
than by cylinder traps, with clear Plexiglas traps posi-
tioned next to apple trees capturing slightly, but not
significantly, more PCs than cylinder traps (Figure 2).
Captures by unbailed versus baited traps did not differ
significantly among any of these three trap types (Fig-
ure 2). However, baited clear Plexiglas traps placed at
the edge of woods captured significantly more PCs
(about 14 times more) than similarly positioned
unbailed traps (Figure 2). In contrast to above find-
ings in commercial orchards, r values describing the
relationship between abundance of PCs in traps and
amount of injury ranged between 0.75-0.89 for unbailed
and baited pyramid and clear Plexiglas traps placed
next to perimeter apple trees. Less encouraging, how-
ever, were r values describing relationship between
time of capture of PCs in traps and time of injury, which

did not exceed 0.22 for any type of unbailed or baited
trap.

Conclusions

Perhaps the most encouraging finding from this
study was the positive response of PCs to baited sticky
clear Plexiglas traps placed next to woods. In the fu-
ture, a simpler and more attractive version of this type
of baited trap could be very useful for monitoring the
beginning, peak and (most importantly) the end of im-
migration of overwintering PCs from woods or
hedgerows into orchards.

The reason why odor bait significantly enhanced
PC captures by clear Plexiglas traps near woods but
not captures by any of the various types of traps placed
adjacent to, beneath or within canopies of perimeter
apple trees is uncertain but could be related to use of
too high a dose of ethyl isovalerate, one of the odors
used a component of the bait. The extra high dose
used here turned out to be about six times greater than
the medium dose found to be attractive in subsequent
tests (see following article) and, at close range for PCs

Fruit Notes, Volume 64 (Number 3), Summer, 1999

Unbailed Baited
Pyramid

Unbailed Baited
Cylinder

Unbailed Baited

Plexiglas at

Perimeter Apple Trees

Unbailed Baited

Plexiglas at

Woods

Trap type

Figure 2. Captures of plum curculios on unbailed and baited pyramid, cylinder, or clear Plexiglas traps in unsprayed
orchards. Bars not superscribed by the same letter are significantly different at odds of 19 to 1 .

crawling toward pyramid, cylinder, or circle traps,
could have negated attractiveness of limonene and/or
grandisoic acid.

None of the unbailed or baited traps placed adja-
cent to, beneath, or within apple tree canopies repre-
sented improvement over traps tested in 1 998 in terms
of ability of trap captures to reflect the time of occur-
rence of PC injury to fruit. It is of little value to spend
more time and effort to deploy PC traps in association
with apple trees if one can not realize a principal ben-
efit of doing so: being able to predict time periods when
PC injury is most likely to occur based on increases in
captured PCs. Further research is needed to achieve
this benefit.

Acknowledgements

We are grateful to the eight commercial growers
(Bill Broderick, Dana Clark, Dave Chandler, Dave
Cheney, Dave Shearer, Joe Sincuk, Tim Smith, and Mo
Tougas) who participated in the study and to Jim
Hardigg in South Deerfield, who permitted use of his
unsprayed orchard at Hardigg Industries. This work
was supported by awards from the New England Tree
Fruit Growers Research Committee, the USDA North-
east Regional Integrated Pest Management Competi-
tive Grants program, SARE, and Massachusetts State
and Michigan State Integrated Pest Management funds.

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Fruit Notes, Volume 64 (Number 3), Summer, 1999

Fruit Odors Are More Attractive tlian
Conspecific Odors to Adult
Plum Curculios

Tracy Leskey, Monica Elmore, Anthony Minalga, Beata Rzasa, E. Fidelma Boyd,

and Ronald Prokopy

Department of Entomology, University of Massachusetts

Many species of weevils are attracted to host plant
odors and to weevil-produced aggregation and/or sex
pheromones. In many cases, when host plant odors
and pheromones are deployed in combination, weevil
attraction is greater than to either odor type alone. Plum
curculios (PCs) have been shown to be attracted to host
fruit odors and to a male-produced aggregation phero-
mone, grandisoic acid, identified in PCs by Eller and
Bartelt of Illinois, but little is known about the level of
PC attraction to a combination of host fruit and phero-
monal odors.

Successful monitoring systems deploying both host
plant and pheromonal odors have been created for sev-
eral species of weevils. Although a reliable monitor-
ing system for detecting adult PC entry into orchards
from overwintering sites does not exist, the deploy-
ment of attractive odors such as those from host fruit
and/or pheromone in conjunction with a trap that is
also visually attractive to adult PCs could prove to be
successful.

In the 1998 Winter issue of Fruit Notes, we pre-
sented preliminary results from bioassays conducted
in large Plexiglas arenas designed to assess PC attrac-
tion not only to fruit odors but also to odors emitted by
other PCs. Here we provide more detailed results of
PC attraction to fruit odors, odors emitted by other PCs,
synthetic grandisoic acid, and fruit odors combined
with odors emitted by other PCs or with synthetic
grandisoic acid.

Materials & Methods

Large clear Plexiglas arenas with dimensions of
24x24x12 inches and Plexiglas lids were used as still-
air arenas for the following experiments. Source ma-
terials to be tested as emitting potentially attractive

odors were placed in small cotton bags hung in the
upper comers (one per comer) of each arena.

Either ten male or ten female PCs starved for 24
hours and chilled 30 minutes prior to testing were re-
leased into the center of an arena at the beginning of
darkness. Numbers of PCs that crawled to within one-
half inch of an odor source held inside a cotton bag
were recorded every 1 minutes for 1 hour. Each trial
was repeated at least eight times, each time rotating
the position of cotton bags containing odor sources.

Treatments tested as potentially emitting attractive
odors included five freshly picked wild plums, five
male or female PCs, synthetic grandisoic acid impreg-
nated into small mbber septa (at a low and a high dose
of 0.03 ug and 3.00 ug, respectively), or five wild plums
in combination with five male PCs, five female PCs,
grandisoic acid at a low or high dose, or a green fmit
worm (GFW) larva. A GFW was used to simulate
plums that had been fed upon by a non-PC insect be-
cause we wanted to leam if odor released from plums
that were being fed upon by PCs and/or odor from PCs
that were feeding on plums was attractive to other PCs.

The total number of PC responders to a particular
odor treatment was tallied over the six 10-minute in-
tervals for each of the four treatments to provide a to-
tal response score for each treatment for every experi-
ment. Results presented here reflect the mean number
of PCs attracted to each treatment over all total response
scores.

Results

Male Responses to Females. In Arena One (Table
1 ), males did not respond to the odor of females alone
compared to controls, but in Arena Two, males re-
sponded to odor of females held with plums in signifi-

Fruit Notes, Volume 64 (Number 3), Summer, 1999

Table 1. Mean numbers of male PCs moving to within 1/2 inch or onto cotton bags of each
treatment in which female PC odors were included in at least one treatment per arena.

Arena

Treatments

One

5 Females
0.9 a

Control 1
1.0 a

Control 2
0.5 a

Control 3

0.4 a

Two

5 Females
0.2 b

5 Plums
2.4 b

5 Females + 5 plums
14.3 a

Control 1
0.4 b

Three

5 Females + 5 plums
14.2 a

Control 1
0.4 c

5 Males + 5 plums
6.4 b

Control 2
0.1 c

Four

5 Females + 5 plums
14.8 a

Control J
0.7 c

lGFW+5plums
8.0 b

Control 2
0.6 c

* Means within rows not followed by the same letter are significantly different at odds of 19:1.

Table 2. Mean numbers of male PCs moving to within 1/2 inch or onto cotton bags of each
treatment in which male PC odors were included in at least one treatment per arena.

Arena

Treatments

One

5 Males
0.9 a

Control 1
0.4 a

Control 2
0.8 a

Control 3
0.5 a

Two

5 Males
0.2 c

5 Plums
5.2 b

5 Males + 5 plums
11.3a

Control 1
0.3 c

Three

5 Males + 5 plums
11.1 a

Control 1
0.2 b

lGFW+5plums
8.1a

Control 2
0.5 b

* Means within rows not followed by the same letter are significantly different at odds of 19: 1 .

cantly greater numbers than to females alone or plums
alone. Males also responded to odor of females held
with plums in significantly greater numbers than to
males held with plums or a GFW held with plums in
Arenas Three and Four, respectively.

Male Responses to Males. In Arena One (Table
2), males did not respond to odor of males alone com-
pared to controls, but in Arena Two, males responded
to odor of males held with plums in significantly greater
numbers than to males alone or plums alone. In Arena

Three, males responded in statistically similar num-
bers to odor of males held with plums and to a GFW
held with plums.

Female Responses to Females. In Arena One
(Table 3), females responded in significantly greater
numbers to females alone compared to controls. Com-
parisons in Arena Two of odors of females alone, plums
alone, and females held with plums yielded statisti-
cally similar responses to plums alone and females held
with plums, though responses to females held with

Fruit Notes, Volume 64 (Number 3), Summer, 1999

Table 3. Mean numbers of female PCs moving to within 1/2 inch or onto cotton bags of each
treatment in which female PC odors were included in at least one treatment per arena.

Arena

Treatments

One

5 Females
3.3 a

Control 1
0.3 b

Control 2
O.Ob

Control 3
0.8 b

Two

5 Females
0.6 b

5 Plums
4.2 ab

5 Females + 5 plums
6.7 a

Control 1
0.7 b

Three

5 Females + 5 plums
7.2 a

Control 1
0.3 b

5 Males + 5 plums
6.6 a

Control 2
0.9 b

Four

5 Females + 5 plums
12.6 a

Control 1
0.4 b

1 GFW + 5 plums
12.3 a

Control 2
0.9 b

* Means within rows not followed by the same letter are significantly different at odds of 19;1.

Table 4. Mean numbers of female PCs moving to within 1/2 inch or onto cotton bags of each
treatment in which male PC odors were included in at least one treatment per arena.

Arena

Treatments

One

5 Males
3.1a

Control 1
0.3 b

Control 2
0.1b

Control 3
0.4 b

Two

5 Males
0.9 b

5 Plums
7.0 a

5 Males + 5 plums
7.6 a

Control 1
0.7 b

Three

5 Males + 5 plums
14.6 a

Control 1
1.1b

1 GFW + 5 plums
6.6 a

Control 2
0.0 b

* Means within rows not followed by the same letter are significantly different at odds of 19: 1 .

plums were significantly greater than to females alone.
Females also responded in statistically equal numbers
to odor of females held with plums compared to males
held with plums and to a GFW held with plums in Are-
nas Three and Four, respectively.

Female Responses to Males. In Arena One (Table
4), females responded in significantly greaternumbers
to males alone compared to controls. Comparisons in
Arena Two of odors of males alone, plums alone, and
males held with plums yielded statistically similar re-

sponses of females to plums alone and females held
with plums and significantly greater responses to both
than to males alone. Females also responded in statis-
tically similar numbers to odor of males held with
plums and to a GFW held with plums in Arena Three.
Male Responses to Grandisoic Acid. Males did
not respond to odor of grandisoic acid at either a low
or high dose in Arenas One and Two, respectively
(Table 5). Statistically similar responses were recorded
for males to plums alone and to grandisoic acid held

Fruit Notes, Volume 64 (Number 3), Summer, 1999

Table 5. Mean numbers of male PCs moving to within 1/2 inch or onto cotton bags of each
treatment in which odor of grandisoic acid, either low (1) or high (h) dose, was included in at
least one treatment per arena.

Arena

Treatments

One

Grandisoic acid (I)
2.0 a

Control 1
1.8a

Control 2
1.9 a

Control 3
2.9 a

Two

Grandisoic acid (h)
1.3a

Control 1
2.1a

Control 2
2.3 a

Control 3
1.4 a

Three

Grandisoic acid (I)
1.1 b

5 Plums
10.0 a

Grandisoic acid (I) + 5 plums
10.5 a

Control 1
0.5 b

Four

Grandisoic acid (h)
1.0b

5 Plums
5.9 a

Grandisoic acid (h) + 5 plums
7.3 a

Control 1
1.5 b

* Means within rows not followed by the same letter are significantly different at odds of 19:1.

Table 6. Mean numbers of female PCs moving to within 1/2 inch or onto cotton bags of each
treatment in which odor of grandisoic acid, either low (1) or high (h) dose, was included in at
least one treatment per arena.

Arena

Treatments

One

Grandisoic acid (I)
3.5 a

Control 1
0.9 b

Control 2
0.6 b

Control 3
0.6 b

Two

Grandisoic acid (h)
2.0 a

Control 1
1.6 a

Control 2
1.8 a

Control 3
1.9 a

Three

Grandisoic acid (I)
1.8 b

5 Plums
11.0 a

Grandisoic acid (I) + 5 plums
5.6 ab

Control 1
2.3 b

Four

Grandisoic acid (h)
1.9 b

5 Plums
5.9 a

Grandisoic acid (h) + 5 plums
7.9 a

Control 1
2.1b

* Means within rows not followed by the same letter are significantly different at odds of 19:1.

with plums at both the low and high dose in Arenas
Three and Four, respectively.

Female Responses to Grandisoic Acid. Females
responded in significantly greater numbers to
grandisoic acid than to controls at a low dose in Arena
One but not at a high dose in Arena Two (Table 6).
Statistically equal responses were recorded for females
to plums alone and grandisoic acid held with plums at

both a low or high dose in Arenas Three and Four,
respectively.

Conclusions

We conclude that females produce an odor that is
attractive to males, but attraction occurs only when
females are feeding on plums. Although females were

Fruit Notes, Volume 64 (Number 3), Summer, 1999

attracted to males alone and synthetic grandisoic acid
alone in significantly greater numbers than to controls,
these responses were quickly lost when host fruit odor
was included. Both males and females were equally
attracted to odors of males feeding on plums and syn-
thetic grandisoic acid held with plums when compared
to plums alone, indicating that attraction to host fruit
odor was not enhanced by the presence of male-pro-
duced or synthetic pheromonal odor. However, syn-
thetic grandisoic acid impregnated into rubber septa
may not have been very attractive due to chemical bind-
ing to septa but could be more attractive if formulated
differently. In general, our studies revealed that fruit-

based odors are the most attractive to PCs and that only
minor contributions are made by addition of conspe-
cific odors or grandisoic acid. Therefore, we conclude
that attractive fruit-based volatiles should be the main
additive to an attractive visual trap to create a success-
ful monitoring system for PCs.

Acknowledgments

This work was supported by Hatch funds and by
the New England Tree Fruit Growers Research Com-
mittee.

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Fruit Notes, Volume 64 (Number 3), Summer, 1999

Several Host-odor Compounds are
Attractive to Plum Curculio Adults

Ronald Prokopy, Starker Wright, Anthony Minalga, Bradley Chandler,

Jonathan Black, and Tracy Leskey

Department of Entomology, University of Massachusetts

Larry Phelan and Richard Barger

Department of Entomology, Ohio State University

As revealed in the preceding two articles, traps devel-
oped for monitoring plum curculio (PC) adults in com-
mercial orchards are unlikely to succeed unless baited
with powerful attractive odor, the most promising type
being attractive host fruit odor. To date, 56 compounds
have been identified as components of odor of plum or
apple fruit at the most attractive stage to PC (2 weeks
after bloom). In the Summer \99%\s,s,\ieoi Fruit Notes,
we presented results of 1 998 tests evaluating 1 6 of these
56 compounds. Two were found to be attractive to
PC: limonene and ethyl isovalerate. Here, we describe
results of 1999 tests in which 30 of the 56 host-odor
compounds (including the 16 compounds of 1998) were
evaluated in field tests for attractiveness to PC.

Materials & Methods

Of the 56 compounds, 46 were identified in the
laboratory by Larry Phelan in Ohio and 10 were iden-
tified in the laboratory of Sylvia Dom in Switzerland.
We chose to evaluate the 30 compounds that were most
readily available from a commercial source (Aldrich
Chemical Company) and least expensive to purchase
(less than $5.00 per gram).

Each compound was introduced into a 2-dram poly-
ethylene vial and assessed at three different rates of
odor release, so as to create a low, moderate, or high
dose of odor concentration in the surrounding air.
Release rates were varied either by adding mineral oil
to the contents of a vial to reduce release rate or drill-
ing small holes in a vial just beneath the cap to in-
crease release rate. Intended release rates for each
compound were 3, 12, and 48 milligrams of odor per
day, but it was not always possible to achieve intended

precision with each compound.

Compounds were assayed in association with yel-
low-green boll weevil traps placed on the ground be-
neath perimeters of unsprayed apple tree canopies in
Massachusetts and Ohio. PCs frequently drop from
host tree canopies to the ground and thus may encoun-
ter odor from a nearby baited trap. Each trap was baited
either with two vials containing the same compound
at the same release rate or two empty vials. Vials were
suspended vertically by wire attached to the base of
the screen funnel top of the trap. Over a 7-week pe-
riod from early May to late June, 360 traps were de-
ployed in Ohio and another 360 in Massachusetts for
compound evaluation. Traps were examined for cap-
tured PCs and rotated in position daily or every other
day.

To measure attractiveness of a particular release
rate of a particular compound, a Response Index (RI)
was created by subtracting the number of PCs respond-
ing to an unbaited control trap (C) from the number
responding to a baited trap (BT), dividing by the total
number of PCs captured by the C and BT traps and
multiplying by 100. Thus RI = [(BT-C)/(BT+C)] x
100. The greater the RI, the more attractive the com-
pound at that release rate.

Results

Results (Table 1 ) show that 1 3 of the 30 compounds
had RI values of 32 or greater (= minimum RI value
for statistical significance) at the most attractive re-
lease rate. In descending order of attractiveness, these
were E-2- hexenal (RI=90), hexyl acetate (67), decanal
(64), limonene (64), geranyl propionate (59), 1-

Fruit Notes, Volume 64 (Number 3), Summer, 1999

Table 1. Response inc

ex (RI) of

plum curculio

adults to 30 host fruit odor compounds evaluated |

at three different release rates

For each

compound, only that release rate

which yielded

the highest RI value of all

(either from

Massachusetts or Ohio)

is given.

Release

Compound

rate

RI*

Benzaldehyde

Low

Benzonitrile

Medium

-7

Benzothiazole

High

Benzyl Alcohol

Low

Decanal

Low

Ethyl Acetate

High

Ethyl Butyrate

Medium

Ethyl Isovalerate

Medium

Geranyl propionate

Medium

1-Hexanol

Medium

2-Hexanol

High

3-Hexanol

Medium

2-Hexanone

Medium

3-Hexanone

High

E-2-Hexenal

Medium

Hexyl Acetate

High

3-Hydroxy-2-butanone

High

Isopropyl acetate

Low

Limonene

Medium

Linalool

High

3-Methyl- 1 -butanone

Medium

-7

2-Methyl-3-buten-2-ol

Medium

1-Pentanol

Medium

2-Pentanol

High

3-Pentanol

Medium

l-Penten-3-ol

High

Pheny lacetal dehy de

High

2-Phenylethanol

Low

2-Propanol

Medium

E-2-Nonenal

Medium

* RI values of 32 or

greater are

; significantly

different from zero at odds of 17 to 1.

pentanol (59), benzaldehyde (46), benzyl alcohol (44),
ethyl isovalerate (40), 2-pentanol (35), 2-hexanol (32),
phenylacetaldehyde (32), and 2-propanol (32).

Conclusions

These results strongly confirm previously-reported
attractiveness of limonene and moderately confirm
previously-reported attractiveness of ethyl isovalerate.
In addition, five other compounds not among the 16
compounds tested in 1998 were found to be notably
attractive here (RI value of 40 or greater): benzyl alco-
hol, decanal, geranyl propionate, hexyl acetate, and 1-
pentanol. Also, two compounds that were among the
16 tested in 1998, but not found to be attractive then,
were attractive here (perhaps because of a more favor-
able release rate here): benzaaldehyde and E-2-hexenal.
These findings offer promise that one or more of these
attractive compounds alone (or together in a blend) at
an appropriate release rate can be applied to visual traps
to substantially enhance capture of PCs.

Acknowledgements

This study was supported by awards from the New
England Tree Fruit Growers Research Committee,
Massachusetts Horticultural Research Center Trust
Funds, the USDA Northeast Regional Integrated Pest
Management Competitive grants program, and Mas-
sachusetts State and Michigan State Integrated Pest
Management Funds.

*JI> *st^ •st'* *st>* •st^

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Fruit Notes, Volume 64 (Number 3), Summer, 1999

Evaluation of Kaolin Clay (Surround^'^)
for Control of Plum Curoulio

Ronald Prokopy and Tracy Leskey

Department of Entomology, University of Massachusetts

Developing an effective trap for monitoring plum
curculio (PC) in orchards would provide a means for
determining the need and time to apply an insecticide
treatment for controlling this pest. The question then
arises of what insecticide to use. For the past 30 or
more years, azinphosmethyl and phosmet have been
the recommended materials against PC. Conceivably,
new regulations under the Food Quality Protection Act
may seriously compromise future use of these and other
insecticides in orchards.

Therefore, in 1 999 we decided to evaluate a new
material, called Surround^'^, as a candidate for con-
trolling PC. It consists entirely of particles of white
kaolin clay, the same clay in fact that is used in porce-
lain pottery. Research to date by Michael Glenn and
Gary Puterka of USDA's Appalachian Fruit research
Laboratory in Keameysville, West Virginia suggests
that insects contacting foliage or fruit sprayed with an
aqueous solution of Surround are not killed but instead
are repelled. Apparently, the clay particles are very
annoying to insects walking on treated surfaces and
cause them to seek food and egglaying sites elsewhere.

Our 1999 tests of Surround against PC consisted
of a small-scale trial conducted in a commercial or-
chard and preliminary trials conducted in the
laboratory.

100 gallons water. A single perimeter tree in another
row did not receive any insecticide against PC and
served as an untreated control. No PC injury was ob-
served in samples of fruit taken prior to insecticide
application. On June 17 (just before June drop), ten
fruit were sampled for curculio injury on each treated
or untreated tree. Only 1/6 inch of rain fell between
May 31 and June 17.

The laboratory trials involved caging PC adults
singly with either (a) one untreated apple or one apple
sprayed with Surround and adjuvant at above rate
(termed a no-choice test), or (b) one untreated apple
together with one Surround-treated apple (termed a
choice test). These trials were conducted in August
using adults that emerged from pupae about 2 weeks
before testing and were starved for 1 day before test-
ing. Apples were examined 24, 48, and 120 hours af-
ter initial exposure for feeding punctures made by
adults (young adults, as used here, are unable to lay
eggs).

Results

Results of the orchard trial showed that averages

Materials & Methods

The orchard trial was carried out at the
Prokopy Orchard in Conway using six rows
of Liberty trees, each with five trees per row.
Every other row was sprayed twice with
Surround: once on May 31 (one week after
petal fall) and again on June 8. Surround
was applied at the recommended rate: 50
pounds per 100 gallons water, along with a
manufacturer-provided adjuvant at 1 pound
per 100 gallons water. Remaining rows were
sprayed once (May 31) with phosmet at the
recommended rate: 1 pound of 70WP per

Table 1. Percent apples injured by plum curculio
adults in commercial orchard trees receiving two
applications of Surround, one application of phosmet,
or no treatment.

Treatment

Number of trees

Injured apples
per tree (%)

Surround
Phosmet
Untreated

15
15

6.0

3.3

30.0

Fruit Notes, Volume 64 (Number 3), Summer, 1999

Table 2. Number of punctures in apples made by newly-emerged plum

curculio adults

confined singly

in laboratory cages with either

one Surround-treated appl

2 together with

one untreated apple (choice

test) or one Surround-treated

apple alone vs

one untreated

apple alone (no

-choice test).

Mean nc

). punctures per

fruit after

Number of

Test

Apples

replications

24 hours

48 hours

120 hours

Choice

Treated

0.0

Untreated

1.7

2.8

4.7

No choice

Treated

0.4

0.8

1.8

Untreated

1.7

3.3

5.8

of 3.3, 6.0, and 30.0% of sampled fruit were injured
by PCs on phosmet-treated, Surround-treated, and un-
treated trees, respectively (Table 1). Results of labo-
ratory trials showed that in choice tests, where adults
could choose to feed on either an untreated or a Sur-
round-treated apple, all feeding occurred on untreated
apples (Table 2). However, in no-choice tests, where
adults remained hungry if they did not feed on the lone
type of apple provided, punctures on Surround-treated
fruit reached about one-fourth the number on untreated
fruit 24 and 48 hours after trials began and reached
about one-third the number on untreated fruit after 1 20
hours.

Conclusions

Our combined findings suggest that Surround has
definite potential as a material for preventing PC in-
jury. In the orchard trial, two sprays of Surround were
about half as effective as one spray of phosmet in pre-
venting curculio injury. In laboratory trials. Surround Acknowledgements
was completely effective in deterring feeding by PCs
on treated apples under conditions where untreated
apples were nearby but was less effective in the ab-
sence of accessible untreated apples. These results
indicate, t


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