Entomology Update: First Generation Codling Moth

The 2019 biofix (first sustained flight) in the Penn State Fruit Research and Extension Center (FREC) orchards was established on May 2. Although the current colder weather somehow slowed down the development of codling moth (CM) eggs, the time to manage this pest is fast approaching. Based on the weather forecast, the 5-10 percent CM egg hatch which corresponds with about 250DD₅₀ after the biofix, in the Biglerville area will occur sometime during the week of May 19, 2019.

The optimal date for the first insecticide application directed against CM larvae varies from orchard to orchard, as it depends on the actual local minimum and maximum temperatures and the biofix date. Additionally, while the simple insect developmental models incorporate the daily max and min temperatures for the calculation of degree days (number of heat units necessary for the initiation of various developmental stages), in some cases it is important also to know how the ambient temperatures directly influence specific behavior.

Codling moth male adults respond to sex pheromone released by the female commonly during the late afternoon and early evening periods. If the temperature at this period is not above the flight threshold (at least low to mid 60°F), CM male moths will frequently not respond to the pheromone. The CM monitoring traps utilizing the sex pheromone will remain empty despite both male and female moths being present in the orchard. The decision about the necessity of the insecticide application should be based on the actual presence of the moths in the orchard as determined by captures in pheromone traps.

Codling moth adults in the sex pheromone trap. Photo: Greg Krawczyk, Penn State

If codling moth is present in the orchard and insecticide treatments are necessary, the recommended, broad-spectrum larvicidal insecticides to control CM include Altacor®, Exirel®, Voliam® Flexi, Besiege ® (all IRAC Group 28), and Delegate® (IRAC Group 5).

A second insecticide application against CM, depending on the pest pressure, is usually needed around 10-14 days after the first application. Although the CM egg hatch model traditionally calls for only two insecticide applications, recently we continue to observe an extended flight of this first-generation codling moth adults sometimes lasting until the end of June. If sex pheromone traps continue to catch significant numbers of CM adults in orchards during June and two applications for CM are already made, then a third insecticide application may be needed during this late period as well.

OFM injured terminal on apples. Photo: Greg Krawczyk, Penn State

If late plum curculio (PC) still needs to be controlled, products with PC activity such as Assail® (IRAC Group 4A), Avaunt® (IRAC Group 22A), Exirel, and Voliam are recommended. Assail, and Avaunt are excellent products to control PC but are less effective against CM. To avoid the development of insecticide resistance, it is important to remember that products with a different mode of action should be used against consecutive CM generations. The active ingredients in Altacor, Exirel, Voliam, and Besiege belong to the same IRAC Group (diamides), so if any of these products are used for the control of the first CM generation, they should not be used for the control of the second or third CM generations.

In organic apple orchards specifically but also in conventional IPM orchards, the Cydia pomonella Granulosis Virus (CpGV) present in products such as Cyd-X®, Cyd-X HP and Madex HP® provides the best alternative to systemic insecticides for the management of CM. In our research trials, weekly applications of the CpGV even at low rates (e.g., 1.0-2.0 fl oz /ac) when combined with mating disruption program provided CM control at levels comparable to insecticide treatments. Madex HP in addition to codling moth neonate larvae should also provide effective control of Oriental fruit moth larvae.

An application of mating disruption (MD) for the management of CM should be considered in orchards with a low to medium CM pressure. Our latest field trials with various mating disruption products for the control of CM and Oriental fruit moth (OFM) documented excellent efficacy of these products. CideTrak®, Checkmate®, and Isomate® mating disruption products are commercially available and should be included as a seasonal CM and OFM program. If MD products are used for the control of CM, the pheromone dispensers should be already placed in orchards (i.e., before CM biofix).

Although the best timing for placing OFM MD products was before the OFM biofix, even delayed placement of OFM MD products should still be effective and reduce pressure from this pest during consecutive OFM generations. In orchards with CM/OFM mating disruption programs, special monitoring lures should be used for the monitoring codling moth (CM DA Combo lure) and oriental fruit moth (OFM Combo Dual lure). In orchards without MD program using of the regular CM LL and OFM LL are sufficient.

Weekly updates on moth captures in pheromone traps located at the Penn State Fruit Research and Extension Center (FREC) in Biglerville.

Other insect pest considerations

In addition to the codling moth, during this time of the season, additional insect pests may require management in many orchards. The leafroller, tufted apple budmoth (TABM) is also active at this time of the year (TABM biofix in the Biglerville area was established on May 05) and should be controlled as well. The timing for the second application CM usually coincides very well with the optimal timing to control TABM larvae. And while controlling CM and TABM with the second and potentially third CM directed applications, other pests such as spirea aphids, European red mites, wooly apple aphids, San Jose scales or early Japanese beetles may also require control.

Early season wooly apple aphid colony on apple branch. Photo: Greg Krawczyk, Penn State

With the bloom related challenges with OFM control, the potential third application against codling moth may also help to control the expected second generation OFM larvae. The 2019 season is also the year for the Brood VIII of the periodical cicada which is expected to pose a significant challenge for fruit growers located in the western part of Pennsylvania. If needed, the choice of the insecticide(s) to control CM should additionally take into account those other pests.

Periodical cicada adults on an apple tree. Photo: Greg Krawczyk, Penn State