May and June Beetles Emerging Soon

During the months of April and May, we begin to see the adult May and June beetles (Phyllophaga spp.) flying around lights or onto window screens, most commonly at night. The female May beetle will usually deposit eggs into the turf in April-May; where as the June beetle will usually deposit eggs in May-June. The eggs will hatch into grub worms that are creamy white in color with brown heads and are “c-shaped.” The grubs feed on dead organic matter and then move to the roots of plants. Since the grubs feed on roots, they can injure roots of grasses and other plants. This causes infested grass to brown and easily removed in large clumps.
Before treating for grub worms, lawns should be inspected to determine the presence of an infestation, which is more than 5 grubs within a square foot. In order to inspect an area, soil sections that are 3 to 4 inches deep should be taken randomly to total one square foot. One square foot of turf can be sampled by removing four, 6 inch square pieces of turf or ten, 4 inch cup cutter core samples. The optimal time for inspection and treatment should be 5-6 weeks after the most beetles are seen. This will ensure that smaller grub worms that are less than ½ inches will be found in the turf.

Some Control Options:

Non-Chemical Control Options:

Maintain healthy turf by fertilizing and watering properly.

Parasitic nematodes in the genera Steinernema and Heterorhabtitis have been shown to be effective against white grubs. They can be purchased and applied to infested areas.

Chemical Control Options:

Irrigating the soil with ¼ -½ inches of water prior to treatment can improve the effectiveness of the insecticides, since the grubs will move closer to the soil surface.
Imidacloprid, halofenozide, thiamethoxam, and clothianidin are some active ingredients found within insecticides that are often applied before extensive grub worm damage is seen, since they are effective on smaller grubs. Lambda-cyhalothrin and trichlorfon are some active ingredients within insecticides that are used when larger grub worms are present.

White grubs. Photo by Texas A&M University.