Small orange or green boxes tied onto trees is just one of the signs that summer is approaching.
The boxes are gypsy moth traps set by trappers working with the Wisconsin Gypsy Moth Slow the Spread Program. The program is preparing for the emergence and flight of the adult male gypsy moth in July.
The gypsy moth is an invasive pest known to defoliate many species of trees and shrubs, especially oaks. However, it is only in the larva or caterpillar stage of life that gypsy moths are most destructive. When they become moths, they spend their two-week lifespan looking for a mate and reproducing.
Trappers will set approximately 29,000 traps in 42 counties by the beginning of July. Traps are used as a method of population survey, not as a method of population control.
"Trapping tells us where the moths are and where they're not," said Chris Whitney, gypsy moth trapping coordinator. "Trapping also helps determine if an area needs spray treatment the following year or if an egg mass survey needs to be done after traps are taken down in the fall to better evaluate the population."
Two different traps are used for trapping: a triangular delta trap, which looks like a small birdhouse, and a milk carton trap, which looks like a milk carton with a roof. A delta trap can hold up to 20 moths, and a milk carton trap can hold up to 1,500 moths.
All gypsy moths caught are males. Female moths cannot fly. Male moths find female moths to mate by following a scent released by females. To catch the male gypsy moth, each trap has a string or strip with the female gypsy moth scent as a lure. The inside walls of the delta trap are coated with a non-toxic glue. When the male moths fly in hoping to find a female moth, they stick onto one of the walls. The inside walls of the milk carton trap are not sticky, but a pesticide strip is present to kill the moths that fly in.
The traps are not harmful to people, plants and animals. When the traps are constructed properly, they should last until the moths stop flying in August. The traps also will not allow birds or small mammals to enter.
The number and type of trap to be used depends on where it is set in the state. In areas where gypsy moths are known to be found, most traps are the milk carton traps. They are set at one trap per nine square miles.
Delta traps are usually set in the western third of the state where gypsy moths are not as common. Delta traps are set to one trap per one square mile. There is no trapping in the eastern part of the state because it is considered generally infested, and trapping does not give any usable data, Whitney said.
People are asked to leave the traps alone should they see one. If a trap needs to be set on private property and the owner is present, trappers will ask the owner for permission to set the trap on the property. Trappers will wear fluorescent vests and carry an identification card. If the owner is unavailable, trappers will set the trap, and leave an information sheet and a phone number to call for more information.
"Most landowners are very cooperative, and we appreciate that," Whitney said. "However, if a landowner wants a trap moved or removed, they should call the number listed on the trap."
For more information, call the toll-free number 1-800-642-MOTH (1-800-642-6684).