June is time to spray for bagworms

Many shade trees and woody ornamentals are affected each year by a large variety of insects. One of the most widely recognized species is the bagworm.

The hatching will peak during the first two weeks of June, and typically lasts four to six weeks. An open-ended, silk lined bag is formed around the newly hatched larvae as protection.

They move slowly in search of food, and as they grow the bag expands and becomes decorated with leave bits.

The most important things when treating for bagworms, is to get the timing right and to thoroughly cover the host plant.

The best time for control is when the bagworms are still small and susceptible to insecticides. This is ideally the last two weeks of June or the first week in July, if infestation was light last year. This delay between hatching and control will ensure that most the larvae have emerged.

If the infestation was severe, immediate treatment may be needed to protect new growth and ensure tree vitality. A follow-up treatment two to three weeks later is needed to kill worms that hatched after the initial treatment.

The majority of these insects will be located deep in the thick interior of the tree so waving a nozzle and misting the tree will only kill bagworms feeding on the tree peripheries.

Each female missed during control can lay up to 1,000 eggs for next years hatch.

Bagworms are notably seen on cedar and juniper trees; however, several broadleaf trees, shrubs and ornamentals also serve as hosts to bagworms.

They have also been reported to feed on clover, ragweed, parsley and nightshade.

Evergreens are much slower at recovering from bagworms because they do not have the ability to produce replacement foliage like deciduous plants. Several years of foliar feeding by uncontrolled bagworm populations may kill established conifers.

Bagworms are not restricted to the host species on which they begin feeding. After defoliating a host, they are capable of migrating on to a new host.

Many companies use the same active ingredient in their respective lines of insecticides; with several products being available to homeowners.

It is not possible to list all of the products available or to know what each store carries; as a result homeowners must rely on active ingredients as a guide to locating a product for their specific problem. For control of bagworms, effective active ingredients include carbaryl, cyfluthrin, permethrin, ad malathion. Always read and follow label directions.

More information on bagworms and other insects is available from the Bourbon County Extension Office.

Editor's Note: Delta George is a K-State Research and Extension agriculture and 4-H extension agent assigned to Bourbon County. She may be reached at (620) 223-3720.