Adult gypsy moths will soon emerge, and the small, bright green or red boxes tied onto trees will show us where they are in some parts of Wisconsin.
The boxes are traps to catch and monitor the invasive gypsy moth.
Trappers from the Wisconsin Department of Agriculture, Trade and Consumer Protection's Gypsy Moth Slow the Spread Program began setting traps in mid-May and will set approximately 19,000 traps total in 50 counties, mainly in western Wisconsin, by early July.
Traps are used as a method of population survey, not as a method of population control.
"Trapping tells us where the gypsy moths are and where they're not," said Chris Whitney, gypsy moth trapping coordinator. "It helps determine if an egg mass survey needs to be done in the fall to better evaluate the population and if an area may need an aerial treatment the following year."
The traps only catch male gypsy moths because they can fly and the females cannot. To find each other and reproduce, the females release a pheromone for the males to detect and follow. This pheromone is undetectable to other insects and is used as a lure in the traps.
"The unlucky male gypsy moths enter the traps and meet their end instead," Whitney said.
The traps will stay in place until the male moths stop flying in August.
"It's important to leave the traps up during moth flight to get the data we need. Then, when the moth flight ends, we'll take them down," Whitney said.
Two different traps are used for trapping: a triangular delta trap, which looks like a small tent, 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.
The type of trap set in an area depends on where it is set in the state. Milk carton traps are set in areas where gypsy moths are known to be found. Delta traps are usually set in the western third of the state where gypsy moths are not as common.
There is no trapping in the eastern-half of the state because it is considered generally infested, and trapping does not provide any usable data.
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. "But, if a landowner wants a trap moved or removed, they can call the number listed on the trap and we can move the trap."
The gypsy moth in its caterpillar stage is known to feed on and defoliate more than 300 different species of trees and shrubs, especially oaks.
For more information, call the toll-free number 1-800-642-6684 or visit the website http://gypsymoth.wi.gov.
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