An easy push-back of the dirt on a Main Street lawn revealed this grub, amongst many others. (Photo by Jayna Smith)

Many Lawns Showing Signs of Grub Infestation

 

Jayna Smith

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Numerous lawns throughout the area are not looking their best, covered in brown patches, likely by the work of grubs.

According to the University of Maine Cooperative Extension, grubs are the soft-bodied larval form of various beetle species, including European chafer, Japanese beetle, May/June beetles, Asiatic garden beetle, and Oriental Beetle.  

These pests have a brown head and six well-developed legs, and when the turf is lifted and grubs are exposed, they can usually be found lying on their sides in a C-shaped position.  

The Cooperative Extension explains that from May through early June, white grubs pupate two to five inches deep in the soil.  Adults emerge from pupae a few weeks later and lay their eggs in the ground during the summer.

As soon as the eggs hatch, they start feeding on the roots of grass until cold weather drives them down another two to eight inches.  When spring arrives, they move back up closer to the surface to continue their feasting.

Signs of white grub damage include wilting or yellowing of grass and can result in large patches of dead or dying turf.  And, if the infestation is bad enough, entire patches of lawn can be rolled back like a rug.  

What can make matters worse is the attraction the grubs are for skunks, raccoons, crows, and seagulls, all of which cause even more damage to lawns when they dig around to feast on the grubs.

Organic options to manage and control the grubs that the Cooperative Extension shared included allowing the birds, skunks, and raccoons to dig up the grubs, then later replant the grass.  Another option is to add nematodes, a type of small, slender worms, to your lawns.  Likewise, keeping lawns dry during the summer may cause the eggs to dry up and die.  But, this of course, will also result in brown grass.

There are chemicals available that can help in ridding lawns of grubs.  The use of trichlorfon is a common method, however, it must be applied by a licensed professional.  As well, it kills only about half of the mature grubs and does not protect the lawn from the next generation of grubs.

According to the Cooperative Extension, preventive controls are what are needed to target the next generation of grubs.  Most preventives are applied in June before the grubs are in the adult stage mating and laying eggs.  Chemicals such as chlorantraniliprole need to be applied earlier because it needs more time to become incorporated into the lawn.

One can learn more by visiting the University of Maine Cooperative Extension website at extension.umaine.edu/home-and-garden-ipm.

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