Early season organic codling moth management
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
Monitoring traps baited with pheromone lures provide important information on the development of codling moth populations within an orchard as well as their relative density. Please refer to the moth monitoring article in today’s Fruit CAT Alert for additional information on trap and lure selection, trap maintenance and trap placement. Traps are used to provide a biofix, which, in the case of codling moth, is the date of the first sustained moth capture (moths trapped on successive days). Establishing an accurate biofix is important because it provides a starting point for the degree day models used to time subsequent insecticide applications. At this time, of year daily trap checks are recommended so that an accurate biofix can be obtained.
Mating disruption has rapidly become the worldwide foundation for codling moth management in both organic and conventional apple farms. When used appropriately, mating disruption will maintain codling moth populations to a low level by greatly reducing the number of eggs laid in each generation. This is important for organic growers, because the insecticidal pest management tools available are not suited to knocking down large populations. However mating disruption alone typically will not provide economic control of codling moth. Therefore, for organic growers to avoid boom and bust cycles of codling moth damaged fruit at harvest, combining mating disruption with OMRI approved, supplemental, insecticides is of critical importance.
Mating disruption dispensers should be hung prior to bloom if possible. For mating disruption to succeed dispensers must be in place prior to the first codling moth flight. Dispensers should be placed in the top quarter of the tree canopy. Research at MSU and elsewhere has repeatedly demonstrated that mating disruption functions better when a higher density of hand-applied dispensers is used and when it is applied over large contiguous areas rather than small blocks. Thus it is suggested that growers apply dispensers at the highest labeled rate. Isomate C+® is currently the only dispenser with OMRI approval.
Supplemental early season codling moth management is largely accomplished through the use of ovicides and larvicides. OMRI approved materials are limited to horticultural oils, codling moth Granulovirus and Entrust®. Use of these materials requires precise timing. Horticultural oil applications are not suggested for early season codling moth management due to a high probability of phytotoxicity when sulfur is present.
Research at MSU and in Europe has shown that Granulosis virus, used in conjunction with mating disruption, provides a powerful one-two punch in driving moth populations down over a period of several years by targeting two different life stages, mating disruption against the adult and virus against the larvae. Granulovirus is a larvicide and should be applied beginning at 250 degree-days after biofix. To be effective, granulovirus should be targeted to coat eggs to ensure that emerging larva will ingest a lethal dose. Granulovirus has a short residual, especially under hot summer conditions, and should be applied during the evening every five to seven days. Research performed at MSU suggests that more frequent applications at a low-labeled rate are more effective than high rates applied less frequently. Frequent application of low rates of virus should also prove to be the most economical program for Michigan apple producers. Three applications of products, such as Carpovirusine, are equal in the price of product used to one application of the high rate. In temperate climates, growers are weekly applying fungicides and or insecticides during codling moth first generation, so the addition of CpGv formulations to the spray tank does not incur additional expenses in time and tractor use. A major advantage of granulovirus for the organic grower is it is extremely specific to codling moth and should not disrupt natural biological control of other pests or resident native pollinators. Several OMRI approved granulovirus products are available including: CYD-X® and Carpovirusine.
Entrust® (Spinosad) is also a larvicide and should be applied beginning at 250 GDD after biofix or the first significant moth catch is recorded. Entrust® has a somewhat longer residual than granulovirus, with reapplications made every seven to 10 days. While Entrust® has been shown to be an effective management tool, it is not species specific, and is toxic to many natural enemies and pollinators. For this reason, Entrust® should be reserved for use in orchards experiencing high populations of CM and, when possible, rotated with granulovirus. Both Entrust® and granulovirus should be applied during the evening hours. This will maximize the residual activity of the products and in the case of Entrust® will limit potential negative impacts on pollinators and natural enemies.
The work of Dr. Gut and Dr. Wise is funded in part by MSU's AgBioResearch.