Grubs

May 14, 2021

This time of year, when you walk into a store you will find a variety of products available for your lawn. Several of these items are not needed now but may be used later. My best example of that is fertilizer. There are rare circumstances when I would recommend fertilizing a lawn in the spring. The same applies to grub worm control.

The life of a grub worm starts in the summer as an egg that hatches into a larva. Its mother may have been one of several insects, Japanese beetle, masked chafers, European chafer, Asiatic garden beetle, Oriental beetle, green June beetle, and May/June beetles. The larva of all these C-shaped insects with a chestnut-colored head will be a white grub worm.

White grubs damage a variety of cool-season grasses while feeding in the soil's organic matter, thatch, and plant roots. It is not uncommon to find mixed populations of two or more species in a yard. Most of these species have a one-year life cycle. The exception being the 3-year life of a June bug.

Most of these hatch out in late July and will feed on the roots of grass then slowly move down deeper into the soil as winter approaches. During the warmer days of late winter and spring, they move back up to the roots, feed a little, then pupate and come out of the ground as adults in May and June. Going out to kill grub worms now is not productive. They have done their damage and the cold soils of spring reduce the effectiveness of the insecticide. Shortly they will be pupating and gone.

Grubs are capable of causing serious damage to the grass. Their feeding causes the turf to wilt and die. Early indications of grub damage may include patchy areas of wilting, discolored or stressed turf that does not respond to irrigation. The grass eventually collapses, resulting in dead or extremely thin patches that may range in size from a few meters to large areas. If you can pick up the sod like a carpet then all the roots are gone. After a rain, pulling the sod back will reveal the white grubs.

There are two different times to use grubworm control depending on the product you use. Preventative treatments are used before you know you have damage. They could be a waste of money and insecticides but there are cases when year after year one section of the yard may be affected and a candidate for treatment.

Products that contain these insecticides can be used in this manner as well as later on after damage starts to show up. They are Chlorantraniliprole, Cyantraniliprole, Clothianidin, Imidacloprid, and Thiamethoxam. They are sold by a variety of brand names and they do last for some time in the soil. So, a treatment in early July will last through egg hatch. These products will work if you go out in late Page 2 of 2 August and see you have a problem. There are also insecticides such as Sevin and Dylox that will also work in late August but are a total waste of money if applied before the eggs hatch.

Sometimes the only way you know that grubs are present is the nighttime activity of raccoons and skunks peeling the sod back to find a meal. This is when one homeowner, upon awakening, described his lawn as looking like a bulldozer had attacked. 

Mark Kepler, Extension Educator- Agriculture and Natural Resources

Purdue Cooperative Extension Service-Fulton County

1009 West Third Street, Rochester IN 46975

574 223 3397 http://www.ag.purdue.edu/counties/fulton/pages/default.aspx https://www.facebook.com/Purdue.Extension.Fulton