The use of the Michigan spray model for codling moth control has been in use for several years by apple growers attempting to incorporate Integrated Pest Management (IPM) practices into their pest control program. To prevent codling moth damage, this model calls for a pesticide application to be made 250-degree days (base 50) after the biofix. Follow up applications are then made, if needed, after an additional two to three weeks. After several years of using this model, one orchard in Wayne County, Ohio began developing significantly higher moth counts in the pheromone traps used to monitor the male codling moths within the orchard. For the first three years of this phenomenon (1999 to 2001), no additional fruit damage was associated with the increase in moth count. However, in 2002 the orchard experienced a greater than 60% loss due to codling moth damage despite intensive spray efforts according to the Michigan model. This has called into question the value of the model as it relates to Ohio conditions as well as the gender ratio in these large numbers of codling moths. The use of passive interceptor traps as well as Multipher traps baited with a vinegar/molasses-based feeding attractant failed in two previous studies to catch enough moths to determine the gender ratio. The development of the pear essence kairomone lure with the attractant ethyl(2E,4Z)-2,4-decadienoate (DA) has given one more option to use to determine this ratio as it is based on a feeding attractant that is attractive to both the male and the female moths.
Monitoring was carried out in two separate orchards in Wayne County. Orchard #1 had three blocks of mixed apples, each having had abnormally high pheromone trap counts since 1999. Orchard #2 also had three blocks of mixed apples, but has not experienced the high numbers of codling moths in its traps. Neither orchard had pear trees within 200 yards of the DA baited traps. Orchard #1 has been monitored for codling moths by the county-based IPM program since 1992, and orchard # 2 since 1995. Each block of apples had three Multipher-3 traps baited with standard Scentry CM lures and one Pherocon-VI delta trap baited with the DA lure. The Pherocon-VI delta trap was used for the DA -baited trap rather than the Multipher-3 trap as it was the type of trap suggested by the supplier (Great Lakes IPM). In addition, each orchard had a Universal Black Light trap (BioQuip Products, Inc.) positioned against a light colored building adjacent to a block of apples. Each black light trap was operated with a timer to turn the trap on at 8pm and off at 2am. The black light traps and Multipher traps used DDVP vapor strips as killing agents. Traps were monitored 2-3 times per week until first catch and weekly thereafter. Traps were set out on April 23. Neither orchard uses mating disruption.
In orchard #1, which has had the history of high trap counts, the first moths were caught in the pheromone traps on May 5th, with an average of 1.55 moths per trap per week. The first catch for the DA lures was on May 12th when one of the three traps within the orchard had captured one male and one female moth. The average trap catch of the pheromone baited traps for this date was 28.2 per trap per week. Table 1 shows the total number of moths caught in the three DA traps each week through August 11th as compared to the average number of moths caught in the nine pheromone traps. No moths were caught in the DA traps after August 11th. Harvest evaluations (1000 fruit per block on 10/4) showed a range of 0.1% to 9.7% damage to the fruit by codling moths among the three blocks.
Table 1. Weekly codling moth catches in DA and pheromone traps 5/05-7/14/2003 in orchard #1
| Date | DA lure (total of three traps) | Pheromone (average of nine traps) | |
| Female | Male | ||
| 5/05 | 0 | 0 | 1.5 |
| 5/12 | 1 | 1 | 28.2 |
| 5/19 | 3 | 4 | 48.1 |
| 5/26 | 3 | 5 | 32.6 |
| 6/02 | 2 | 2 | 33.4 |
| 6/09 | 1 | 0 | 21.8 |
| 6/16 | 0 | 1 | 41.9 |
| 6/23 | 0 | 0 | 27.0 |
| 6/30 | 0 | 0 | 25.6 |
| 7/07 | 0 | 0 | 21.0 |
| 7/14 | 1 | 2 | 9.7 |
| 7/21 | 0 | 0 | 1.2 |
| 7/28 | 0 | 0 | 10.1 |
| 8/04 | 0 | 0 | 10.4 |
| 8/11 | 1 | 0 | 13.6 |
| Total | 12 | 15 | |
| Gender percentage | 44.4% | 55.6% | |
Orchard #2 had no moths caught in the DA traps throughout the season. The date for the first moth catch in the pheromone traps was May 20th at 1.8 moths per trap. This also happened to be the highest average number of moths caught for the first flight. For the second flight, the highest average for the pheromone traps was 3.7 moths per trap on August 5th. Due to heavy hail damage sustained by this orchard in late June, no harvest evaluation was done.
In neither orchard did the use of black light traps result in any useful information. Continuous rainy conditions for much of the season may have been part of the reason for this as what was caught in the traps was difficult to identify due to rain getting into the collecting bucket. These wet conditions may also have been part of the reason for the low incidence of codling moth damage in comparison to 2002, which was a very dry year. The Codling Moth Information Support System web site: http://ippc.orst.edu/codlingmoth/bionomics/humidity.html mentions "Hagley (1972) found that rainfall was the most important cause of mortality of the first instar larvae when they were just beneath the epidermis of the fruits. Gier (1963) suggested that mortality of first larval instar occurred because of increasing water contents of the fruits and consequent flooding of tunnels. The second and third instar larvae in the fruits are also affected by the rainfall." This may also offer an explanation to the fact that throughout the season as well as while doing the harvest evaluations in orchard #1 that most of the fruit damage found was a superficial sting rather than actual tunneling.
1) Though the pear essence kairomone DA lure is capable of attracting both sexes of the codling moth, it appears that it is only effective in our region when moth numbers are high (10+ per trap) as indicated by pheromone traps. This would make the use of the DA lure unacceptable for the purpose of determining an initial spray date. The ripening of fruit during the second flight may also be a factor that may interfere with the attractiveness of the lure to the moths at that time.
2) Though the number of moths caught in the DA traps was low as compared to pheromone traps, the ratio of male to females caught did indicate a fairly even balance between the two genders.
Appreciation is given to the Ohio Fruit Growers Society and the Ohio State Universtiy
Integrated Pest Management block grant for the funding used to complete this project.
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