Across Wisconsin most regions have accumulated around 250 degree days (DD) since the start of the sustained codling moth flight, also known as biofix (late May in most orchards). This threshold of 250 DD indicates that larvae are beginning to hatch, and would be particularly susceptible to an insecticide application. A monitoring threshold of 10 moths per trap is used to determine if the population of codling moth is high enough at your orchard to warrant an insecticide application at this time. According to John Aue of Threshold IPM, unusually high trap catch numbers (30-70 moths per trap) were seen this May, possibly because the late, sudden spring caused populations to be more condensed temporally, instead of spread out across several weeks (see DATCP pest bulletin volume 63, number 6).
The following information on monitoring and on using insecticides to control codling moth was first published last year in volume 2, issue 4 of this newsletter. For information about using mating disruption to control for codling moth, please refer to that article.
Larval control is still an important aspect of codling moth IPM, and the effectiveness of a larvicide can be greatly increased by monitoring and using a degree day model to improve spray timing. If you are not using mating disruption this summer, you can monitor populations using a commercially available CM pheromone lure at a rate of one trap per ten acres. Traps ideally should have been set out prior to bloom, at about head height in the tree canopies. It is especially important to check the traps every few days until you find the first “sustained trap catch”, or when there is on average more than one moth per trap on two consecutive nights.
That date of first sustained trap catch is used for CM as a “biofix”, or as the time when you begin accumulating degree days. First sustained trap catch represents the point at which moth flight begins, and therefore when egg laying begins. Approximately 250-300 degree days after this biofix the majority of the larvae will have hatched, but will not yet be inside an apple, which is the optimal time to spray a larvicide for CM. Degree days can be calculated using your own weather station data (see article explaining degree day calculations in the second issue of this newsletter), or a regional degree day accumulation can be found using the NEWA website and Cornell’s CM model.
A list of available insecticides to control CM in apple is provided in the following table. There are many other tradenames available, and we do not recommend these that are listed above other options. All product recommendations can be found in the latest Midwest Fruit Pest Management Guide. Additionally, you should always fully read and follow the label before spraying any pesticide.This article was posted in Insects and tagged CM, Codling Moth.