University of Illinois Evaluations of Insect Control
in Apples, Urbana, Illinois, 2000
Rick Weinzierl, Mark Hurt, and John T. Shaw

Summary

Plot Information and Methods

Location

University of Illinois Pell Farm, Urbana, Illinois.

Experimental Design

Randomized, complete block, 3 replications per treatment; 3 to 6 trees per rep per treatment

Agronomic Factors

Apple cultivars: 'Red Delicious' (Rep 1), 'Golden Delicious' (Rep 2), and 'Jonathan' (Rep 3).

Application dates: Treatments began at petal fall. Surround (2 rates) was applied weekly for 6 weeks, then on approximately a 14-day interval. All other treatments were applied on roughly a 14-day interval. Treatment dates for Surround were: May 5, 12, 19, and 26, June 2, 9, and 22, July 6 and 21, and August 3. All other treatments were applied on May 5 and 19, June 2, 15, and 30, and July 14 and 28.

Weather Information

See Appendix A, Table A.1 and Table A.2.

Method of Insecticide Application

All insecticides were applied with an FMC-320 air blast sprayer calibrated to deliver 100 gpa at 100 psi and 3.0 mph.

Post-Treatment Evaluations of Injury

On July 13, we examined up to 300 fruits per treatment to assess visible codling moth injury. We did NOT pick fruit at this time. We also rated injury by Japanese beetles and assessed European red mite infestations by counting mites on 30 leaves per rep per treatment. Harvest samples were picked on September 6, and up to 300 apples per rep per treatment were examined individually to assess insect injury and presence.

Statistical Analysis

The percentage of fruit infested with or damaged by target insects was calculated for each rep of each treatment. Percentage values were arcsine-transformed and analyzed using a 2-way ANOVA, with significance set at P = 0.05. Means were separated using Fisher's Protected LSD (P = 0.05). Means listed in Tables 9.1 and 9.2 are means of raw data. No statistical analyses were applied to the mid season mite counts (in this trial) or the assessments of Japanese beetle injury.

Results and Discussion

Mid-season evaluation, July 13, 2000

Mid-season assessment indicated a trend that would hold true at harvest as well: Intrepid, Avaunt, and Guthion had protected fruit from injury through mid July; SpinTor and the two Surround treatments were less effective. There was some concern that Surround treatments might favor spider mite outbreaks; our counts did show some very minor buildup of European red mite on trees treated with the higher rate of Surround, but this infestation did NOT increase or cause injury. As expected, only Guthion protected foliage and fruit from Japanese beetle injury; less injury was apparent in the Surround treatments than in Intrepid, Avaunt, and SpinTor treatments.

Harvest Evaluation, apples picked September 6, 2000

Harvest samples confirmed the value of Intrepid (at either rate), Avaunt, and Guthion for codling moth control. SpinTor was less effective (though not statistically significantly so), and Surround was not effective for season-long codling moth control. Injury by the true bugs (Lygus bugs and stink bugs), plum curculio, early leaf rollers and green fruit worm, apple maggot, and fall leaf rollers (red banded leaf roller and tufted apple bud moth) was too light and/or too variable to allow determination of the value of the insecticides tested. Early season rainfall was frequent; Surround may have been more effective in a dryer season or if more frequent applications had been practical.

Table 9.1: Mid-season evaluation of insecticides applied to apples, Urbana, Illinois, 2000.

Treatment

Rate¹

% Codling
moth-damaged
fruit²

European red
mites per leaf

Japanese beetle
damage to foliage

Intrepid

8 fl oz

0.0

c

<0.1

Mod

Intrepid

16 fl oz

0.3

c

0

Mod-High

Avaunt

0.11 lb a.i.

0.7

c

<0.1

Mod

SpinTor

5 fl oz

6.3

bc

0

Mod

Guthion 50W

0.5 lb a.i.

0.0

c

<0.1

Very Light

Surround

25 lb

17.5

b

<0.1

Light-Mod

Surround

50 lb

10.5

bc

1.8

Light-Mod

Untreated Control

34.0

a

0.1

Mod-High

¹ Rates are specified as unit/acre.
² Means in a column followed by the same letter are not significantly different (P=0.05).

Table 9.2 Mid-season evaluation of insecticides applied to apples, Urbana, Illinois, 2000.

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% fruit damaged by:

Treatment

Rate¹

Lygus bug, stink bug, or similar*

Plum
curculio
oviposition*

Spring leaf roller or gree fruit worm*

Codling
moth¹

Apple
maggot*

Fall
leaf
roller*

Intrepid

8 fl oz

1.2

12.3

0.5

0.0

b

1.5

0.0

Intrepid

16 fl oz

2.0

11.8

0.7

0.3

b

3.5

0.0

Avaunt

0.11 lb a.i.

1.7

7.0

0.3

0.5

b

0.5

0.3

SpinTor

5 fl oz

2.8

14.2

0.5

17.5

b

0.5

0.7

Guthion 50W

0.5 lb a.i.

2.4

3.3

0.5

0.5

b

0.0

0.2

Surround

25 lb

1.7

9.0

0.0

57.0

a

1.0

1.5

Surround

50 lb

0.0

7.8

0.0

49.8

a

3.0

1.8

Untreated Control

3.0

12.8

0.3

45.8

a

2.2

0.5

¹ Rates are specified as unit/acre.
² Means in a column followed by the same letter are not significantly different (P=0.05).
^{* Means within this column do not differ significantly at P = 0.05.}