MORRISVILLE, N.Y. — Many landowners have been alarmed by the large population of gypsy moths this year. These elevated populations can cause noticeable leaf damage to a variety of tree species. Although deciduous trees can usually withstand 2-3 successive years of defoliation without being killed, the defoliation can make the tree more susceptible to other pests and disease. Evergreens do not regrow leaves as easily as deciduous trees and are more likely to die if they become defoliated.
Gypsy moths have several stages of their life cycle: egg mass, caterpillar, pupa, adult moth. The egg masses are 1 1/2 inch long by 3/4 inch wide, covered with a dense mat of buff-colored hairs. Mature larvae are slate colored and have 2 rows of blue spots (5 pairs) followed by 6 pairs of red spots on the back. Pupae are brown and teardrop shaped. Male moths are brownish with black markings and have a wingspan of 1 to 1 1/4 inches. Females have white wings with dark markings and a tan to buff colored body. The good news is, they only feed on leaves while they are in the caterpillar stage.
Ready to start defending your trees? Here are some steps you can take:
Gypsy moth caterpillars and adult moths can be killed by squishing them. Some people are allergic to the hairs of the gypsy moth, so be sure to wear gloves, protective clothing, and a dust mask.
- Sticky barrier bands may be placed around the tree’s trunk to catch the caterpillars. This is usually most effective in late April.
- Create a burlap trap by wrapping a piece of burlap around your tree. Tie a string around the center of it and fold the top half down. Squish the caterpillars that get caught between the two pieces of burlap.
- Once the caterpillars go into their cocoon or pupa stage, you can squish the cocoons.
- If you see moths emerging from the cocoons you can squish them, to prevent them from laying eggs.
- During the fall and winter, look for egg masses. Scrape any you find into a container of soapy water and let soak for about 2 days.
- If you have small, young caterpillars next spring, the leaves can be sprayed with a microbial/biological insecticide Bacillus thuringiensis (kurstaki), commonly known as BT or BTK. You will have to weigh the benefits vs the cost of spraying, and keep in mind that the spray may have an impact on beneficial, native insects, birds, and other animals.
Although these practices may help protect your individual trees, they will do little to reduce the overall population of gypsy moths in a given area.
If you would like more information, please contact us at our office: Cornell Cooperative Extension of Madison County, 100 Eaton Street, Morrisville, NY 13408 | 315.684.3001 | madison@cornell.edu or contact Ag Subject Educator Megan Henderson at meh363@cornell.edu and (315)684-3001 ext. 126.
CCE MC on: Facebook @ CCEMadison, Instagram @ CCEMadisonCounty, Website @ MadisonCountyCCE.org
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–Megan Henderson
Cornell Cooperative Extension Madison County
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