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Japanese Beetle News

Current information for homeowners and agricultural producers

Japanese Beetle FAQ (Frequently Asked Questions)


Question: Why do Japanese Beetles congregate in mass?

Answers: Adult beetles congregate in an area for two reasons. First, females release a pheromone (mating attractant) as they feed, drawing males to that general location, which also begin to feed. Secondly, the first beetles in an area release another set of chemicals that draw later emerging beetles/other area beetles to these "preferred" feeding sites.

Question: How far can Japanese Beetle adults fly? Adult

Answers: Japanese Beetles can fly at least a couple miles to reach preferred feeding stock, and they likely will fly further if given the chance.

Question: What about egg-laying?

Answers: Female beetles lay eggs throughout their life, which lasts only about 1-1.5 months. The bulk of those eggs may be laid within the first couple weeks of an individual female's adult stage. Female Japanese beetles can lay dozens of eggs before they "pass on." Some report that eggs are impacted negatively by desiccated conditions, indicating possible population reduction when conditions are dry during the egg laying period (questionable data). Controlling adults to reduce grub damage to turf or controlling grubs to reduce adult feeding damage is not effective because the adult beetles are very good fliers and will enter the landscape from other areas.

Question: Does a hard winter kill off more JB grubs than normal thus decreasing problems with adults?

Answers: Generally speaking, a hard winter may not eliminate many grubs. Grubs migrate down in the soil profile during the fall. They may migrate a few inches deep or they may go as deep as 8 inches. At 5-8 inches, grubs would likely avoid even fairly intense frost layers.


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