First gypsy moth spray window opening

Gypsy moth is hatching in the southern Lower Peninsula. The first spray windows are opening for nursery and Christmas trees growers.

The warm weather is moving gypsy moth development along and hatch should be beginning in parts of Michigan’s southern Lower Peninsula this week. If you grow spruce, fir and Douglas fir for Christmas or nursery stock and ship these into non-quarantined areas, you must apply an approved pesticide during the spray window.

Gypsy moth
Gypsy moth feeding on leader of Colorado blue spruce.

Gypsy moth spends the winter in buff-colored egg masses in shelter areas. These eggs hatch in the spring and the young caterpillars spread to new locations by crawling to the tops of trees where they spin a silken thread and are caught on wind currents. Once they settle, they will begin to feed and develop for about seven weeks until they are approximately 1.5 to 2 inches long. Typically, this occurs in early summer – June to early July. They then enter a pupal or transitional stage. The spray window targets the time between the time they disperse, develop and begin to pupate.

Michigan State University Extension says to make sure to use adequate volume and methods to obtain optimum spray coverage of plant material. Proper application of any product is essential for control to be effective.

Since gypsy moth development will vary by location, you will need to monitor development around your farm. Weather conditions will affect caterpillar development and the end date of the spray window. Remember, we have the gypsy moth treatment window tool on Enviro-weather. This program allows you to track the opening and closing dates of the gypsy moth spray window by county.

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