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Grubs
Grubs are the larvae of insects such as Japanese beetles, European chafers and Oriental beetles. They are usually creamy white and C-shaped.
Grubs live underground and feed on grass roots. When infestations are severe, turf will look wilted and won't revive even when watered. Damage usually shows up in August and into September when cool-season grasses are stressed.
Birds and small mammals may also damage turf while feeding on grubs. Just because there is animal damage doesn't mean that there are enough grubs to treat. Animals often come back to the same spots looking for grubs even though their numbers may be low.
Late July through September is a good time to scout for grubs to see if there are enough to justify treatment:
- Peel back about 1 square foot of turf.
- Count the number of grubs.
- Sample a few areas about 20 yards apart.
- Note where animals are feeding and damaging turf and sample those areas.
- Replace sod and water.
Treatment may be justified above the following threshold levels:
- Japanese beetle grubs: More than 10 grubs per square foot.
- European chafer: 5 to 10 grubs per square foot.
- Oriental beetle: 8 grubs per square foot.
The different species of grubs are distinguished by their raster patterns, which takes some practice. See Identifying White Grubs at the University of Massachusetts Turf Program site for more information.
Adults of these species lay eggs in late June through July. The grubs hatch and go through a series of stages called instars. The young instars feed at the soil/thatch interface. Treating for grubs in spring as they near maturity is often not effective. Pesticide applications, if needed, should be while the grubs are still young and vulnerable. Sometime in August is usually best.
For more, see Grubs In Your Lawn? from the New York State IPM Program.
Chinch bugs
 Chinch bugs are surface-feeding insects. Adults are up to ¼ inch long, and black with white wings. Look for the distinctive black triangle where their wings overlap.
Damage is most severe in drought years, and can be prevented by planting endophytic enhanced varieties of perennial ryegrass, fine leaf and tall fescues. Regular moisture (without overwatering) increases levels of naturally occurring fungi that help keep chinch bugs in check.
To scout for chinch bugs, cut both ends out of a coffee can and press it at least 1 inch into the soil. Fill it with water. Chinch bugs and other insects will float to the surface.
There are no specific thresholds established for the number of chinch bugs that justify treatment. But this technique will let you know if they are present.
 Cutworms
Cutworms are surface feeders. Look for gray-brown-black caterpillars between 1/8 and 2 inches long that curl into a C when disturbed.
Cutworms feed at night. If you suspect a problem, scout for them with a flashlight.
 To monitor, mix 2 to 4 tablespoons of dishwashing soap in a gallon of water. Sprinkle over about 1 square yard of turf. Cutworms will come to the surface in about 10 minutes. Flush the area with fresh water to prevent injuring turf.
Sod webworms
 Sod webworms are surface feeders. Look for young caterpillars with black heads. Adults are up to ¾ inch long, brown to green with dark spots. Adult moths had snout-like mouthparts.
Signs of feeding include chewed grass blades and fecal pellets.
To monitor, mix 2 to 4 tablespoons of dishwashing soap in a gallon of water. Sprinkle over about 1 square yard of turf. Webworms will come to the surface in about 10 minutes. Flush the area with fresh water to prevent injuring turf.
Prevent damage by planting endophytic enhanced varieties of perennial ryegrass, fine leaf and tall fescues.
Bluegrass billbugs
 Bluegrass billbugs are surface feeding insects. Adults have a distinctive snout.
You can often spot them crossing driveways and sidewalks migrating to lawn in the spring. Look for sawdust-like feces where they are feeding.
Prevent damage by planting endophytic enhanced varieties of perennial ryegrass, fine leaf and tall fescues.
© Copyright, Department of Horticulture, Cornell University.
Website design: Craig Cramer cdc25@cornell.edu
Mention of trade names and commercial products is for educational purposes; no discrimination is intended and no endorsement by Cornell Cooperative Extension or Cornell University is implied. Pesticide recommendations are for informational purposes only and manufacturers' recommendations change. Read the manufacturers' instructions carefully before use. Cornell Cooperative Extension and Cornell University assumes no responsibility for the use of any pesticide or chemicals. Some of the links provided are not maintained by Cornell Cooperative Extension and Cornell University. Cornell Cooperative Extension and Cornell University are not responsible for information on these websites. They are included for information purposes only and no endorsement by Cornell Cooperative Extension or Cornell University is implied. Cornell Cooperative Extension provides equal program and employment opportunities.
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