lawn grubs/

Asked October 20, 2019, 8:58 AM EDT

I have a problem with grubs in my front yard they have eaten a large area on the lawn. How do I get rid of them without the use of chemicals? I also want to replace the grass with plugs. Is now the right time?

New Castle County Delaware

1 Response

Managing white grubs without the use of chemicals is challenging. White grubs typically are digging deeper into the soil this time of year to avoid freezing temperatures. However, I spoke recently with someone else dealing with white grubs and they claimed they still have them at the soil surface. Grubs at the soil surface (just below the roots) are susceptible to a variety of insecticides. A hard frost or two will force beetles to dig deep into the soil. Culturally, you can try to minimize damage and populations by not watering the lawn much during adult Japanese beetle activity (June - mid-August) and then watering the lawn in mid-August through September if we are dry like we were this year. This only makes conditions less favorable for the grubs to hatch from eggs in the summer and helps keep plants hydrated once surviving grubs are feeding on grass roots.

If you do not wish to use insecticides then there are commercially available entomopathogenic nematodes (Heterorhabiditis bacteriophora), small wormlike animals, that will search out and attack white grubs. These are not harmful to people or pets - they are only insect pathogens (meaning they kill insects). Milky spore is not a viable option because our white grub complex typically is dominated by either chafers or oriental beetles. Milky spore only works on Japanese beetles and takes multiple years of multiple applications at high rates to obtain any efficacy. There is a relatively new product called BeetleGone on the market that may provide some control of the white grubs. It is an insecticide but made up of Bacillus thuringiensis galleriae (similar to the B.t. kurstaki available for bagworm and other caterpillar control).

A good time for lawn renovation is shortly after Labor Day through early October. It is getting late to be renovating a lawn. Lawn renovation is typically with reseeding or sod. I am unaware of anyone using plugs to renovate a lawn or grub damaged area. The only exception I am aware of is if the person is installing zoysia or bermuda grass. Lawns can be seeded or sodded in the spring but it is not ideal. Challenges with spring seeding/sodding often revolve around grass development and root growth. Plants germinating in the spring have a difficult time growing enough roots to survive the drier and hotter summer that will occur in a couple months. Planting in the fall provides the grass opportunity to grow roots into November and the following spring before summer arrives.

The grubs present this fall will resume feeding next spring, but grass is typically growing its best in the spring; therefore treatments for grubs in the spring is rarely warranted.