June 1996 - Volume V, Issue 6

Grub Control Update

David M. Kopec, Extension Turfgrass Specialist

White grubs are the larvae of certain scarab beetles which feed on the roots of turf and other soft rotted shrubs. In general, the larvae are laid in June to early July by the adults. The adults are the bulky bodied "June" beetles, which are attracted to porch lights this time of the year. They usually crawl around on the concrete, fly up towards a light, and sit looking for a mate. They are short lived as adults, and the adult beetles do not damage the turf.

After mating, the female lays eggs on the turf which then develop into small grubs. The grubs feed on the roots during the summer and then in the fall go deeper into the soil staying there through the winter. They feed to a lesser degree the next spring and turn into adults usually by early June. There are several types of "June bugs" and all of them feed on turf.

The best time to control the grubs is during mid-July, when the grubs are small, have sensitive skin and are close to the surface. Damaged turf is off color, being light green, yellow and thinned out. Severely damaged turf can be pulled back in small patches. Pesticide applications include classics such as; Oftanol, Turcam, Triumph, Dursban, Sevin, Proxol, Dylox and Diazinon.

Some new materials coming on the market include MERIT (imidacloprid). When ingested by the grub, this product causes the grub to stop feeding. This is catastrophic for a young grub when applied in July to early August. Another material which may be available for the 1997 season, is called RASTER (halofenozide). It interferes with the molting (skin exoskeleton shedding) of grubs, but does not affect other insects. It has a low mammalian toxicity (LD50 of 2850). Another strain of the Bacillus thuringensis (Bt) product is available from Mycogen. This new item is the "buibui" strain of Bt. The trade name of this strain is called Bt-M-Press. Bt is active against Japanese beetle larvae, but to the best of my knowledge, it's not active on the other grubs we have in Arizona. 

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