The Purdue Plant and Pest Diagnostic Laboratory

What's Hot at the P&PDL on
August 13, 2007

Grub Damage and Irrigated Turfgrass (Double Jeopardy)

Timothy J. Gibb, Extension Diagnostian, Department of Entomology, Purdue University

We often receive questions about how the drought may ffect grub damage in turfgrasses. Where turfgrass goes dormant during a drought, most grubs will not survive. In these cases, no chemical grub controls need be applied. However, remember that a drought tends to concentrate egg-laying Japanese beetles and masked chafers into areas of irrigated turfgrass. Eggs require moisture and during severe drought years, newly hatched grubs can only survive and feed where soil is irrigated. This means that in many areas of the state right now, well-maintained turfgrasses are at an even higher risk of developing grub damage than in normal years. Add to this increased risk of grub pressure the fact that extended heat and drought reduces the natural root growth and development
of grass plants.

The bottom line is that some irrigated turfgrasses under drought conditions are much more susceptible to even light grub feeding injury this year than in most years. Where protection against grubs is required, do not delay. Early August is the optimal time to make an application of any of the preventative treatments. (After mid September, Dylox is usually the best curative product to apply.) Be sure to water chemical treatments in thoroughly and remember that control may be especially difficult in thatchy turf.

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Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service