Information on BTK

Sited Information

Information has been adapted from the Purdue University Cooperative Extension Service West Lafayette website
Original information by Cliff Sadof and Jodie Ellis, Department of Entomology, Purdue University
Adapted for the Itasca website by Fred Maier, Village of Itasca Environmental Services.

FAQs About Using BTK to Control Gypsy Moths

What Is BTK? How Does It Kill the Gypsy Moth?

BTK (Bacillus thuringiensis var. kurstaki) is a bacterium found naturally on leaves and in soil. These bacteria act as tiny factories that produce protein crystals that kill specific groups of insects.

When eaten, the protein crystals tear the cells that line intestines of susceptible insects, causing lethal bacterial infections. The source of infection can be the BTK itself or any of a number of species of bacteria already present in the insect’s gut. Death occurs within a few hours to a few weeks after the insect ingests BTK.

How Is BTK Insecticide Used to Kill Gypsy Moth?

In Itasca, BTK applications are applied from helicopter to areas where gypsy moths threaten trees. A series of 2 sprays is applied in late May to early June, when caterpillars are small and most susceptible to BTK. BTK sprays are used to prevent or reduce defoliation and nuisance problems.

What Is the Gypsy Moth? Why Is It a Problem?

The gypsy moth is an insect with a big appetite for oaks. Each caterpillar can grow up to 2 inches long and can consume up to 11 square feet of foliage from early May until June. When abundant, caterpillars can completely defoliate trees. Although healthy trees can survive defoliation, repeated removal of leaves can kill a tree.

Older, less vigorous trees suffering from drought can be killed by a single defoliation. Capable of feeding on 500 different kinds of plants, this pest threatens Itasca forests and suburban landscapes.

Gypsy moth caterpillars are also a public nuisance in recreational and residential areas that are known for their oaks. The rain of caterpillars and their excrement from treetops can discourage even the heartiest residents from taking a walk in the park. Some people develop rashes or allergies to caterpillar hairs that float through the air.

Is BTK Insecticide Sprayed On Any Food Crops?

Yes. BTK is widely and safely used on many edible crops, including fruits and vegetables. In fact, BTK can be applied on food crops the day they are harvested.

Is BTK Insecticide Dangerous?

BTK has been safely used to kill gypsy moth in the northeastern United States since 1980. BTK does not cause disease in people, mammals, birds, or fish. BTK has been reported to cause minor and temporary irritation to exposed skin, eyes, ears, noses, or throats in a small number of individuals.

However, numerous studies of large communities of people exposed to BTK during aerial sprays have repeatedly failed to find any significant adverse risks to the health of the general public.

Staying indoors during sprays is a good way to minimize exposure to BTK. Plan on remaining indoors for at least 10 minutes after airplanes have finished spraying. Wait until spray or dew has completely dried before allowing children to play outside. If for some reason you come in contact with BTK spray, wash the affected area with soap and water.

Will BTK Sprays Kill Butterflies?

Yes, but they will not eliminate them. BTK only kills butterflies and moths that are in the caterpillar stage at the time of spraying. Most of Itasca’s butterflies are not in the caterpillar stage until over a month after gypsy moth sprays are completed. This allows plenty of time for the BTK protein to break down and vanish. Furthermore, only some parts of Itasca are targeted for spray. Butterflies outside the spray area are not affected and will quickly re-populate sprayed areas.

Honeybees, ladybugs, and most beneficial insects are not affected by BTK.

Will BTK Damage the Paint On My Car?

No. Some people living in spray areas have reported finding a fine dust on their cars after spraying, but this easily washes off and does not harm the finish.