Without any intervention, codling moth numbers increase about four-fold from generation to generation. Therefore, targeting the first generation is important to reset the population size to a minimum. Control measures for subsequent generations can be adjusted to the local pest pressure indicated by trap counts.
What’s in the pest control toolbox?
The targets for pest management are adult mating, eggs and neonate larvae which are controlled by mating disruption, ovicides, and larvicides, respectively. The combination of these three tools has proven most effective in keeping fruit damage below the economic threshold.
· Mating disruption – the first line of defense – delays and prevents mating and egg laying. Mating disruption dispensers need to be in place by 100 DD or bloom, before the first adults emerge, and typically last all season long. Mating disruption is particularly effective as the temperatures increase and dramatically improves the activity of pesticides applied during the season.
· Ovicides are the second line of defense. Eggs can be prevented from hatching with topical or residual pesticides. Oil is a preferred option; it suffocates the eggs that have been laid. Its residue is short – only about 1 day, but that also means it has little effect on natural enemies. In addition, Trichogramma parasitoids have been shown to help suppress codling moth populations by attacking the egg stage.
· The third line of defense are larvicides, such as conventional larvicides or codling moth granulosis virus. Both target the newly hatched codling moth larvae which almost immediately bore into the fruit. Therefore, precise application timing is important, because once larvae enter the fruit, they are protected from pesticides.
As above, optimal CM control requires the use of MD and generally 1-2 sprays in the spring. The first spray should be an oil treatment (1%) that is applied at 375 DD. This allows you to delay the first cover spray to 525 DD. In conventionally managed orchards, the first cover spray should last 14-17 days and a second spray can be applied if your damage was excessive the previous year. Unless there is a large amount of movement into your orchard from exterior sources, you are unlikley to need more sprays, but should monitor damage and population trends in codling moth traps as recommended by DAS.
In organic orchards, mating disruption is even more important because most organic materials do not have as long a residue (typically half that of conventional insecticides). The first spray should be an oil at 375 DD. Oil (1%) can be applied at 150 DD intervals (this is the length of the egg development period) after the first application to cover the first generation egg hatch period. The egg hatch period is mostly over by 975 DD and MD will reduce any reproduction by that time. This means no more than 4 total oil sprays would be needed.
Virus sprays in the first generation are not recommended because the residue is so short (5-7 days) and the activity period rarely reaches the 150 DD residual activity of oil. After the first generation (if needed) virus is a good option as the 5-7 day residual activity period is easily longer than the 150 DD residue of oil. The use of the oil in the first generation and virus (if needed) in the second generation is also good for resistance management.
As a general goal, the number of larvae reaching the overwintering stage should be kept as low as possible. The occurrence of a full fourth generation of codling moth adds more diapausing larvae to the overwintering population, unless orchards are protected. Low overwintering numbers, however, lay a good foundation for soft and low-input programs in the following year.
Prepared by Matthew Jones, Ute Chambers, and Vince Jones, May 2019