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White Grub Alert!

June 8, 2009
by Rick Brandenburg

By Callie Freeman and Diane Silcox

If you have spent much time outdoors this week you have probably noticed that Japanese beetle adults have begun their yearly emergence once again. The adult is a mostly oval, metallic green beetle with coppery-brown wings. As an adult, the beetles wreak havoc by feeding on more than 300 species of woody landscape and ornamental plants. The immature grub stage of the Japanese beetle inflicts damage to turfgrass by chewing off roots near the soil surface. Early signs of a grub infestation are a thinning and yellowing of the turf that cannot be alleviated with increased irrigation. Turfgrass then begins to die in irregular patches that increase in size. Masked chafer adults have also made an appearance in the coastal areas following the recent rainfall. These beetles are yellowish-brown and have a distinctive black band or “mask” across the head and eyes. Masked chafers do not feed as adults and are active predominately at night searching for mates. Adults are highly attracted to lights and large numbers may be observed at porch lights especially following heavy rains. Immature grubs of the masked chafer exact the same type of damage as grubs of the Japanese beetle. Although we have received no reports of green June beetle activity, they are sure to follow suite in the next few weeks. Adult green June beetles are larger than the Japanese and masked chafers beetles and are mostly a deep green color with a golden, polished underside. Green June beetles are active during the day, flying low over the turf searching for mates and feeding on overripe fruit as well as tree sap. Green June beetle grubs do not feed actively on turfgrass roots but prefer decaying organic matter. These large bodied grubs instead damage turf stands by burrowing and pushing up mounds of soil much like miniature moles!

The most important turfgrass-infesting species of white grubs in North Carolina exhibit one-year life cycles. The adult beetles emerge in mid-May to early June and start to lay eggs. The eggs hatch in July and the larvae begin to feed on the roots of the turfgrass. The larvae will feed all summer until the temperatures cool down in the fall. In November, third instar larvae burrow deeper into the soil to overwinter. The larvae return to the root zone to begin feeding when temperatures warm up in the spring. The larvae will then pupate and the adults emerge in mid-May to early June and perpetuate the life cycle.

Now is the time to apply preventive chemicals to avoid potential damage from large grubs later in the fall. These chemicals have a long residual window meaning they reside in the soil for 60 to 90 days and provide control of young grubs as they hatch from their eggs. Areas with a history of white grub infestations should be targeted with this control approach. There are many chemicals now labeled for preventive grub control so be sure to check the new Ag Chemical Manual or talk with your distributor. Whichever product you choose, whether liquid or granular, be sure to water it in!

For more information please see these related Articles: 

Callie Freeman is a PhD Candidate in Turfgrass Entomology under William Neal Reynolds Professor, Dr. Rick Brandenburg Diane Silcox is pursuing her Master’s degree in Turfgrass Entomology also under Dr. Brandenburg.

Japanese Beetle Life Cycle 
Japanese Beetle Life Cycle

White Grubs 
White Grubs