Pest: Major Pests
The gypsy moth (Lymantria dispar) defoliates hardwood forests and has weakened many acres throughout the northeastern states. It is native to Europe and northern Africa but was brought to Massachusetts from Europe in 1869. Since then, it has spread southward through the northeastern states into southwestern Virginia and a major front is approaching Tennessee as a rate of seven miles per year.
The presence of gypsy moth has been detected in Tennessee every year since the beginning of the statewide trapping program in the 1970’s. Once a positive identification has been made, an extensive pattern of traps are installed around that location. These traps help the Tennessee Department of Agriculture understand the source, extent, and direction of a possible infestation. Often, infestations can be eradicated through elaborate trap placement but sometimes spray operations are necessary. To date, there are no gypsy moth populations in Tennessee.
The Department of Agriculture and various partners install 12 to 14 thousands orange or green Delta traps statewide. These traps are placed in a grid-like pattern that covers rural and urban environments. The traps contain a lure that attract male moths, and once in the trap, the moth is confined by a thick layer of glue. Personnel check the traps weekly for any moth catches. If a suspect moth is found in a trap, the trap is sent to the Forest Health Specialist or the State Entomologist for identification. Five replacement traps are installed at that location to attract any other male moths that might be in the area. If more moths are trapped, an elaborate pattern of traps is installed the following year to begin eradication procedures. If necessary, ground or aerial applications of pesticide is used to fully eradicate the infestation.
The gypsy moth egg masses are laid from middle June to early July. These masses are oval in shape, about 1 inch long and are covered with fine tan colored hairs. The female moth usually lays her egg masses in bark crevices, on the underside of branches, or under decks, chairs, firewood, or lawn furniture. The eggs hatch in early to middle April when the hardwood trees start producing leaves. The caterpillars are 1/16th of an inch long and go through five to six growth stages before entering the pupal stage. The larvae increase in size through each growth stage and develop five pairs of raised blue dots followed by six pairs of raised red dots on its back. They are covered in dark bristly hairs and easy to spot. The caterpillars feed on hardwood leaves and often cause significant defoliation. Adults emerge June through July, depending on temperature and elevation. The adults do not have mouth parts and only have around one week to mate before dying.
The gypsy moth travels in three main ways: crawling, ballooning, and hitchhiking. Female moths cannot fly. When the female emerges from pupation, she crawls to a sheltered spot and waits for a male. Once she has mated, she lays her egg masses on trucks, cars, camper, etc. which hitchhike hundreds of miles away. The gypsy moth caterpillars move around by ballooning or by producing a fine silk thread that catches the wind and takes them to other trees. They can, however, travel hundreds of miles in one day if transported by humans.
Cultural practices such as fertilizing, watering, or pruning help to keep trees healthy and strong if infested. Planting tree species that the gypsy moth do not like such as ash, bald cypress, black locust, yellow poplar, sycamore, red cedar, or holly can help. Reduce the number of place where the female moths can hide egg masses by keeping outdoor articles and debris under cover or inside. If a population is detected, it can be eradicated through intensive trapping, or aerial or ground application of either biological or chemical pesticides. Silvicultural treatments such as pre-salvage thinnings, sanitation thinnings or post-outbreak harvests are options if the threat of a gypsy moth outbreak is near or present in a forested environment.
What Can You Do?
Learn to recognize the egg masses, caterpillars, and adults. Thoroughly inspect your vehicle, camper, outdoor furniture, and firewood for egg masses if traveling from a known area of gypsy moth population. If an egg mass, caterpillar, or adult is found, immediately contact your county agent, professional forester, or the Division of Forestry at 615.837.5432. Early detection is very important to preventing major infestations. Do not move firewood.