Apr 7, 2021
Combating Destructive Fruit Moths

(Sponsored) Burgeoning codling moth and Oriental fruit moth populations are raising a red flag with Pennsylvania entomologists monitoring these pests.

“In the last two years, we have seen a drastic increase in the number of loads of harvested fruit rejected due to the presence of codling moth and Oriental fruit moth in the fruit,” says Greg Krawczyk, Ph.D., Penn State University Extension tree fruit entomologist, at the 2021 Mid-Atlantic Fruit and Vegetable Conference.

Across Pennsylvania in 2019 and 2020, populations of codling moth and Oriental fruit moth were similar to levels documented from 2005 to 2007 when fruit producers had limited tools to control those two pests.

Fruit loads rejected by Pennsylvania fruit processors increased from a low of about 60 loads in 2018 to more than 400 loads in 2020.

In 2020, Krawczyk’s trap counts from May to June were drastically higher than usual, and higher-than-normal daily temperatures are likely to blame. Codling moth and Oriental fruit moth are mostly active late in the afternoon and captures in pheromone traps generally increase when late-afternoon and dusk temperatures are above 62 F.

The seasonal development of these two species differ as they respond to various developmental threshold temperatures and relative heat unit (degree day) accumulation. Oriental fruit moth development thresholds are 45 to 90 F, while for codling moth they are 50 to 88 F, Krawczyk says.

In more than two decades of research, Krawczyk has never seen Oriental fruit moth activity begin later than April 26. For codling moth, the biofix, defined as sustained flight of the moths, usually happens in the first or second week of May.

Despite 2020 being the warmest year on record in Pennsylvania, the relatively cold weather in May of 2020 did not lower pest numbers; however, it did slow development and changed the optimal timings for effective management.

Effectively controlling both pests requires a well-timed insecticide application, combined with mating disruption efforts. With the unique behavior of young larvae entering the fruit shortly after egg hatch, proper timing of insecticide applications is crucial.

Codling moth and Oriental fruit moth deposit eggs on the fruit surface or on tree foliage. Approximately 24 hours later, eggs hatch and the larvae move inside the fruit. Once there, insect control becomes nearly impossible.

Both codling moth and Oriental fruit moth are internal fruit feeders. While codling moth feeds exclusively inside the fruit, Oriental fruit moth can feed within the fruit and in growing shoots. Codling moth is found in pome fruit, and Oriental fruit moth infests apple, pear, peach and nectarine crops.

Krawczyk recommends making your first insecticide spray for codling moth control at 5% to 10% egg hatch, and the second when 50% to 55% egg hatch has occurred.

“The differences in biofix and temperatures between various years can result in two or more weeks for each application,” he says. “The ideal first treatment for Oriental fruit moth in 2017 occurred around April 18. In 2020, the correct timing was about May 4.”

Krawczyk says growers currently have three distinct modes of action that offer effective control and minimal impact on beneficial insects. Those include spinosyns, diamides and granuloviruses, but the residual activity of granulovirus products is limited to a maximum of seven days.

The lone spinosyn product, Delegate^® WG insecticide, is in a class by itself. Delegate offers a mode of action found nowhere else in the market with fast knockdown and lasting control of destructive pests, minimal impact on beneficial insects and a short four-hour re-entry interval.

Delegate effectively controls insects and various worms through translaminar, contact and ingestion activity. Delegate is also an ideal rotational partner, providing maximum management flexibility.

“If you choose an effective product, apply at the right rate at the correct timing and have good coverage, we still believe it should be effective at managing codling moth and Oriental fruit moth,” Krawczyk says. “You have to have the right product to be effective, but if the timing is wrong it doesn’t matter what product you use.”

Contact your local Corteva Agriscience representative or visit Delegatewg.Corteva.US to learn more about how Delegate^® WG insecticide can protect your apple crop against tough fruit pests.