Ohio

Using Feeding Attractant Based Traps to Determine the Effect of Gender Ratio on the Use of Michigan State Codling Moth Control Model

Ron Becker, Program Assistant Agriculture and IPM
OSU Extension, Wayne Co.

Background:

Codling moth is one of the more destructive pests in Ohio apple orchards. For this reason, monitoring for codling moth is an important practice for any apple grower striving to use an Integrated Pest Management (IPM) based pest control program. In carrying out this monitoring, pheromone traps have been used to track the presence and relative size of the moth flight. Along with a degree day model developed at Michigan State University, the weekly catches of the male moths provided by pheromone traps have been used to determine an "as needed" spray program to keep direct fruit damage from codling moth larvae to a minimum.

Beginning in the summer of 1999, an orchard in the Wayne County Extension IPM program started having higher numbers of moths in its traps when compared to other orchards in the county as well as to its own history. Before 1999, the use of these traps along with the Michigan spray model indicated a need to spray for codling moth only once or twice per season. In 2001, this had increased to seven sprays per season due to average trap catches being over 10 per trap for 13 of the 21 weeks that counts were taken. The average of three traps per block was as high as 78 per trap in 2000 and 48 in 2001. In all three years, however, minimal fruit damage was observed, even in areas of the orchard where spraying was not as intensive as indicated by the Michigan model. This brought into question the spray threshold indicated by the Michigan Model. Specifically it called into question whether the catch of male moths in the pheromone traps could be directly correlated to the relative abundance of female moths and the resulting damage of the larvae. Similar concerns about the validity of the Michigan threshold have been expressed recently by other midwestern entomologists

Though recent work in Washington State orchards had shown that the number of female moths caught in passive interceptor traps could be correlated with fruit damage, an attempt to duplicate this study in Wayne County, Ohio in 2001 produced poor results. The current study, conducted in 2002, instead made use of a feeding attractant to attract both male and female moths to help determine the ratio of male and female moths present. The mixture, using molasses, vinegar and ammonia, has been time tested (as mentioned in the 1952 Agricultural Year Book "Insects"). By using these traps, it was hoped to increase information on the ratio and distribution of male and female moths in individual orchards, which in turn would result in better-timed spray applications for controlling the codling moth larvae.

Objective

To evaluate the use of feeding attractant based traps compared to pheromone traps and how the number of female codling moths caught in them related to the Michigan Codling Moth Control model.

Method:

This study was conducted in a single block of mixed apples on the Moreland Fruit Farm near Wooster in Wayne County, Ohio. This is one of three blocks of apples within the orchard. The orchard also contains peaches, cherries, grapes, blueberries, raspberries and a variety of vegetables. The orchard is bordered on the south and west by a state wildlife area, on the east by a dairy farm and on the north by a mix of woods and fields of row crops. On 5/1, twenty Multipher traps baited with long life codling moth lures and containing toxicant strips were distributed in a grid pattern within the block. The traps were placed in every 6th row with four traps in each row. The first and fourth traps in each row were placed in the trees on the ends of rows. The traps were placed at chest height with approximately 80 feet between traps within the row. Multipher traps that had never had pheromone lures in them were placed in the 9th and 20th rows in a similar pattern on 7/8, just prior to the emergence of the second moth flight. The 20th row had only three traps with one on each end and one in the middle. The bait used in these traps consisted of 1-cup cider vinegar, 1/3-cup dark molasses, 1/8-teaspoon ammonia, and enough water to make 1-1/2 quarts of liquid. 1/8 cup of this bait was placed into the bottom of each trap in a small plastic cup. Baskets made from wire screening were then made to fit inside the trap to assist in removal of the moths and keep the moths out of the bait. Toxicant strips were then placed in the bottom of the baskets.

Trap counts were taken weekly and weather was monitored with a Watchdog 450 weather monitor to help track degree-days from biofix and previous spray dates.

Observations:

In the traps containing the molasses/vinegar bait codling moths were found on only three occasions and only in one of the seven traps. Two moths were found in the trap on 8/5, two were found in the trap on 8/12 and three moths were in the trap on 8/19. Due to the low results in these traps, sexing of the moths was not carried out.

In the grid of pheromone traps, as in the past several years, numbers were high. Traps with the highest numbers were on the border of the block. Chart A shows the average daily catch of all traps each week. The total number of moths caught in a single trap in a single week was as high as 85 (6/04/02). Chart B shows the average daily catch for the traps located on the border of the block verses that for the traps in the inner portion of the block. It can be seen that there was a significant difference between the border vs. the inner traps during the first generation. This could indicate that the majority of the over-wintering population had migrated into the block rather than being a resident population. Chart C goes further to show a comparison of the three borders of the block where traps were located for the first flight. This would tend to indicate that this migration came primarily from the south. Moth numbers in these same traps for the second flight were not consistently higher for any one border over another.

A significant difference this year over the past three years was that there was very heavy damage to the crop in 2002. In 1999-2001, despite high numbers of moths in the pheromone traps, less than 5% of the fruit showed damage from codling moths. However, in 2002 the damage on a tree-to-tree basis was estimated to be 50-90% of the fruit showing damage, with an overall crop loss estimated to be 60-70%. The damage varied more according to cultivar rather than location within the orchard (inner vs. border area). The cultivars showing the most damage were Thew Gold, Jonathan and Ida Red. This damage occurred despite an intensive spray program for control of the codling moth.

The date used for the biofix was 5/13/02. The table below shows the insecticides applied, rates and degree-days since the previous application (or biofix for the first application) as well as cumulative degree-days since the biofix. The targets for spray intervals were 250 DD following biofix for the first application and 200 DD between applications after that as long as trap counts remained high. Suitability of the weather for spraying often prevented spray applications at the prime time according to degree-day accumulations.

Table 1. Chemical controls applied to control codling moth in 2002

DateInsecticide(Active Ingredient)Rate of application (A.I.)DD* since biofix or previous applicationCumulative DD* since biofix
6/1Phosmet 2.1 lbs/A189189
6/19Phosmet2.1 lbs/A341530
6/28Phosmet2.1 lbs/A243773
7/31Tebufenozide.28lbs/A861**1634
8/10Phosmet2.1 lb/A 2391873
8/20 Azinphosmethyl1 lb/A2642137
8/31 Methomyl.6 lbs/A2502387
9/10 Methomyl.6lbs/A2382625

*Degree days were calculated on a high-low average base 50 degrees F.
**The longer interval between applications was due to low trap counts during the weeks of 7/01-7/15.

Summary:

This study was unable to demonstrate any reliability in the use of Multipher traps baited with a molasses based feeding attractant to measure the relative density of female moths to male moths within the monitored orchard. However, the data collected from the grid of pheromone traps was useful in indicating the probability that the population of codling moths present during the first flight was due to migration rather than from an over-wintering resident population. It was found that the wildlife area to the south contained a grove of walnut trees, also known to be a host to codling moths. The phenomenon of several years of high codling moth counts with little resulting damage followed by a year with heavy pressure was not entirely unexpected. Dr. Bruce Barrett of Missouri State University indicated similar occurrences in the Missouri area. This does not explain, however, the failure of the spray program used in 2002 in this orchard. Also, still in question is the validity of the Michigan spray model, especially in circumstances where moth counts are historically high throughout the season. Further studies are warranted for both of these questions, especially since the incidence of high moth counts and failure to control codling moths in apples is increasing throughout the eastern part of the country.

For further information contact Ron Becker OSU Extension, Wayne County or the Ohio IPM Office.

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