Codling moth management decision-making - Part I: Bloom to petal-fall
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.
Putting together a sound codling moth pest management program requires that the practitioner understand several decision-making criteria: moth population pressure as measured with pheromone-baited traps in each farm block, the relative effectiveness of the control tactics available, the mode of action (how they work) of the various options, the lifestages each is active on, the optimum time to apply them, and what other pests are controlled if the product is applied at that time. In this first of two articles, we provide information on early season management of codling moth adults and eggs. The timing and options for controlling larvae will be covered in next week’s Fruit CAT Alert.
Another cool spring season in 2009 has reaffirmed the variabitlity of codling moth catches from one farm to another, and from one block to another on the same farm. This is not surprising considering that the extent of early season codling moth activity in an orchard is typically associated with how well the pest was controlled in the previous season. Regional information is a part of understanding colding moth activity, but the use of monitoring traps in individual orchard blocks is the only accurate way to know what is happening on your farm and to make economically sound codling moth management decisions. Growers need to weigh the evidence of moth activity as measured by monitoring traps to decide if treatment is justified in terms of cost and time, and to assist them in determining the appropriate time to treat. To get the most benefit from a codling moth control measure, growers should treat a block after moths have been captured and the accumulation of growing degree days (GDD) required for a particular action as indicated in Table 1 has taken place after the catches were recorded.
Table 1. Codling Moth GDD Model and the earliest insecticide timings
|GDD° Base 50 (Post Biofix)||Event||Action|
|Pink bud||Development of overwintering larvae||Set traps|
|0 GDD° = Biofix (~200 DD° after Jan 1)||1st sustained moth captures||Set DD° = 0|
|100 GDD°||Start of 1st generation egg laying||Timing for 1st treatment for egg targeted materials|
|250 GDD°||Start of 1st generation egg hatch||Timing for 1st treatment if over threshold (for larva targeted materials)|
Targeting the adult lifestage using mating disruption
The first opportunity to control this troublesome pest is to target the adult stage using pheromone-based mating disruption. Pheromone products for this season should already be in the orchard, as they need to be operating when the first moths emerge from overwintering sites. Mating disruption works by inhibiting male moths from finding female moths, thus interrupting the reproductive part of their life cycle. With less mating there are fewer eggs and ultimately fewer larvae to infest fruit. It also means that the population that needs to be controlled with insecticides will be smaller. Apple growers participating in the Michigan area-wide mating disruption project for multiple years have been able to reduce the number of insecticide applications needed to achieve codling moth control by an average of 60 percent. With mating disruption as the foundation for managing codling moth, apple growers can more comfortably employ the reduced-spray programs discussed subsequently in this article. Ours and the experience of many Michigan growers is that programs combining the use of mating disruption and insecticides as needed provide better control than insecticide-only programs.
The first option for controlling codling moth once mating has taken place is to target the egg stage of the life cycle. Among the newer insecticides for codling moth control registered over the past few years are the insect growth regulators Esteem and Rimon. Both act by suppressing development within the egg, as well as larvae that consume it. Hatching of eggs laid by treated adults will also be inhibited. Eggs are particularly susceptible to these products when laid on top of sprayed residue, thus sprays are timed earlier than most other codling moth control materials. Suggested timing for the first application is biofix plus 100 to 150 growing degree days. At this timing, Rimon will provide good to excellent control of Oriental fruit moth, obliquebanded leafroller and spotted tentiform leafminer, while Esteem will be highly active on rosy apple aphid and San Jose scale.
Intrepid is an insect growth regulator that provides good control of codling moth with a residual action of about 10-14d. This product is an insect growth regulator that primarily affects codling moth larvae, but also has substantial activity on eggs, and has sublethal effects on adults. The best results have been achieved by taking advantage of the ovicidal and sublethal effects. For example, applying an early spray at biofix plus 150-200 GDD or a delayed timing of 350 GDD. At the early timing, Intrepid will also control obliquebanded leafroller larvae that are still present in orchards harboring high numbers of this troublesome pest. The addition of an agricultural adjuvant is recommended to improve initial spray deposition. As a cautionary note, growers should be aware that populations resistant to OP compounds might also be resistant to Intrepid.