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Japanese Beetles Emerging in the Rain!

Japanese BeetlesTim Gibb, Entomology Department, Purdue University

How will the rain affect the white grub populations this year? Wet weather this spring will have little effect on grub populations. Japanese beetle adults are just starting to emerge in southern Indiana, and will emerge in full force throughout the state within the next few weeks.

This development is just about right on track for a normal year. A wet spring and early summer will have little affect on grub damage this year because damage is largely controlled by the weather in August and September. If we have a relatively dry August and September, grub damage may be significant. Conversely, if it stays wet in August and September, the turf will be able to tolerate significantly more grub feeding and direct damage will be minimal (but that doesn't take into account the indirect damage from crows, raccoons, and skunks).

The bottom line is that the rainy weather experienced thus far should not modify your grub control plans for later this summer. As always, if you've had high grub populations and damage in a given area last year, it's likely to occur again this year and an insecticide may be necessary. If an area has no grub history, it's not likely that it will have a grub problem this year and thus an insecticide is not justified.

Please refer to the Entomology extension publication E-75 Japanese Beetle (PDF 42K - Requires Adobe Acrobat to view and print) for a list of chemical control options.

The information given herein is supplied with the understanding that no discrimination is intended and no endorsement by the Purdue University Cooperative Extension Service is implied. Any person using products listed assumes full responsibility for their use in accordance with current direction of the manufacturer. Purdue University is an equal opportunity/equal access institution.

Information listed is valid only for the state of Indiana.

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