SPRINGFIELD, Ill. ? At hundreds of farms and yards across Illinois and neighboring states, Japanese beetles are having their annual feast. Beetle activity reaches its peak by mid-July, experts said.

The beetles have been so thick in southern Illinois that traps had to be modified so they didn’t have to be dumped more than twice a day, said Ron Hines, a crop scientist at the university’s Dixon Springs Agricultural Center. A single trap in Massac County caught more than 155,000 beetles last week, he said Thursday.

The beetles are a pest in more than fruit bushes. They have a voracious appetite for roses, attack Japanese maple and linden trees, and can cause havoc in corn fields if they chew off the silk that carries pollen necessary to produce kernels.

Some pesticides, such as carbaryl and cyfluthrin, slow the beetles, but they’re effective for only a few days and before long more beetles come to replace those killed by the chemicals.

Japanese beetles rarely kill a tree or bush; instead, most of their damage is aesthetic.