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Fall armyworm on corn

AUBURN UNIVERSITY, Ala.Fall armyworms continue to plague many areas of the state. While usually known as a pest in lawns, pastures and hay fields, fall armyworms can also be a nuisance in vegetable gardens. With high populations this year, more and more gardeners are looking for ways to keep their vegetables off of the menu.

Scouting

Fall armywormsFall armyworms have a few distinct characteristics that make them easy to identify. Their head has markings that look like an upside-down Y. At the end of their body, the caterpillars have four black dots that form a square.

Ayanava Majumdar, an Alabama Cooperative Extension System entomologist, said when scouting for these pests, there are several things to look for.

“Gardeners should check for fall armyworm caterpillars underneath the leaves, and check for egg masses on soft leaves and stem terminals,” Majumdar said.

When scouting for the caterpillars, it is best to look during the cooler parts of the day. This is when they will be actively feeding.

Damage

Gardeners can also watch for infestations by looking for the damage that armyworms cause. While they prefer grassy crops, once those are gone, armyworms will move on to all kinds of horticultural crops.

As caterpillars, they are especially threatening to small, weak plants that are outdoors.

“Caterpillars will first go after the leaves or foliage on a plant,” he said. “After that, they will also cause damage to both unripe and ripe fruits.”

The damage on the fruit will appear as round holes, often on the top of the fruit. After making these holes, the caterpillars may enter the fruit and feed inside.

Egg-laying moths are a big threat on larger plants that are in an enclosed environment, such as a high tunnel or greenhouse.

Control

Fall armywormsIf an infestation is discovered, there are several chemical control options for home gardeners. Majumdar recommends that gardeners consider using an organic insecticide for control.

“The majority of organic insecticides are easily available through online vendors and the farm supply stores scattered around the state, making them a great choice for home gardeners and small farmers,” he said.

When applying any chemical product, always make a fresh solution for each application and follow all insecticide labels. A list of home garden insecticides for controlling fall armyworms in vegetables (both organic and conventional products) are listed in the Home Garden Vegetable: Insect Control IPM Guide.

Control Items to Remember

There are a few items that gardeners should consider when controlling fall armyworms.

The overall persistence and effectiveness of insecticides are greatly impacted by the weather. A second application may be necessary if a rain event occurs after the first application. If the first application fails to control the pests, do not use a product with the same mode of action for the second application.

Majumdar encourages home gardeners to be selective and timely with applications. Once the fall armyworms are under control, stop applying the insecticide.

“Overuse of an insecticide may increase the chance of resistance, pest resurgence (a secondary pest, such as spider mites, becoming a major issue) and loss of natural enemies,” he said.

For Future Reference

While controlling a current infestation is important, it is also important to plan for next year’s garden pests. Majumdar said making plans to implement a pest exclusion system in a garden will help with pest control next year.

“Pest exclusion systems, both permanent and temporary types, are extremely effective at blocking moths and reducing the overall number of armyworm caterpillars early in the growing season,” Majumdar said.

The Alabama Extension content piece Temporary and Permanent Pest Exclusion Systems for Vegetable Production provides an excellent discussion of the benefits of each type of system.

More Information

Gardeners and producers can download the Farming Basics mobile app for help with caterpillar identification. Through the app, people can contact a regional agent for identification and management recommendations suitable for their area. Updates on various pest activities are also available  by subscribing to the Alabama IPM Communicator Newsletter.

For more information on fall armyworms, visit www.aces.edu.

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