How to Treat White Grubs and Nematodes in the Lawn

Overview

Both white grubs and parasitic, microscopic nematodes create dead or thin areas of the lawn. Not all struggling lawns are the result of grubs and nematodes, but healthy lawns bounce back from a wide range of problems, including subterranean pests. These pests are nearly impossible to eradicate completely, but with patience and legwork, you can protect your lawn.

Step 1

Take multiple samples of soil, 3 inches under the soil surface, from various areas of the lawn. Mix the samples and place roughly 2 cups of the soil in a waterproof container, such as a resealable plastic storage bag, and take it to your local county extension office. Ask specifically for a nematode test. Do not allow the samples to dry out or expose them to sunlight, cold or heat; this kills the nematodes.

Step 2

Look for white, C-shaped grubs just under the turf and within the root zone when digging. Count the number of grubs; more than five grubs per square foot may overwhelm the lawn.

Step 3

Prevent stress on the lawn. Keep lawns 2 to 3 inches high when mowing. Aerate compacted turf and top-dress the lawn lightly with compost or an appropriate fertilizer in late spring. Parasitic nematodes do not respond to pesticides. However, healthy lawns cope with average nematode infestations or white grub damage.

Step 4

Water the lawn deeply, allowing the lawn to dry between watering. This encourages root growth deep into the soil where moisture is more abundant and lessens the lawn's stress during drought or hot weather. A well-formed root system also rebounds from nematode and grub damage.

Step 5

Treat serious white grub infestations with commercially-produced nematodes that prey on the grubs or, in severe cases, pesticides. The nematodes are not toxic to earthworms, people or pets and may overwinter in the lawn, providing protection through the next spring. If using mild pesticides, such as imidacloprid, treat the lawn in June or July, before the eggs hatch. Stronger pesticides, containing trichlorfon or carbaryl, kill young grubs in spring or fall.

Tips and Warnings

  • Never expose beneficial, grub-killing nematodes to sunlight or extreme temperature changes. Sunlight kills nematodes within minutes. Stronger pesticides kill grubs, but also kill earthworms. Use these products as a last resort.

Things You'll Need

  • Gloves
  • Shovel
  • Plastic resealable bags
  • Compost
  • Beneficial nematodes (if necessary)
  • Pesticide (if necessary)

References

  • University of Florida IFAS Extension: Nematode Management in Residential Lawns
  • Michigan State University Extension: Home Lawn Grub Control in Michigan
  • Alabama Cooperative Extension: Controlling White Grubs on Lawn and Turf
  • Environmental Action Barrie: Living Green--Organic Grub Control
Keywords: treat white grubs, treat nematodes lawn, control grubs lawn

About this Author

Kimberly Fuller has been a writer for 15 years, and holds a Bachelor of Arts degree from the University of Utah. She has written successful grants for local schools as well as articles for Demand Studios, Constant Content and other online sites.