Wednesday, April 22, 2009

The May Beetles Are Here!

As the weather warms, we will begin to see the adult May beetles (Phyllophaga spp.) flying under lights at night. These adults feed on leaves of several trees including oaks and pecans and can cause complete defoliation of the tree if large numbers of adults appear. Most healthy trees recover quickly from complete defoliation, but stressed trees can be damaged by these attacks.
The female May beetle will deposit eggs into the turf and the eggs will hatch into “c-shaped” grub worms that are creamy white in color with brown heads. The grubs feed on dead organic matter and roots of plants. Since the grubs feed on roots, they can injure roots of grasses and other plants. This causes infested turf to brown and it can be easily removed in large clumps.

Some Control Options:

Irrigating the soil with ¼ to ½ inches of water prior to treatment can improve the effectiveness, since the grubs will move closer to the soil surface. Parasitic nematodes in the genera Steinernema and Heterorhabtitis have been shown to be effective. Insecticides containing imidacloprid, halofenozide, and clothianidin are some active ingredients that are effective at killing the smaller stages of grub worms and ideally should be applied 6 weeks after adults emerge. Lambda-cyhalothrin and trichlorfon are some examples of active ingredients more effective at killing the larger grub worm stages.

Picture of grub worms. Photo by Texas A&M University.

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