September Lawn Check for Chafer Grub Damage

Chafer grubs are causing widespread lawn damage this year following a hot, dry summer. The plump, white, C-shaped larvae feed on grass roots, and a key treatment window closes by mid-October when they burrow deeper into the ground.

A combination of drought and late-season rain has created ideal conditions for a surge in these pests. Drought-stressed grass cannot regrow roots fast enough to withstand even a small grub population. Also, well-irrigated lawns and garden borders provide the soft, moist soil adult beetles prefer for laying eggs.

Brown or dormant grass can mask the early signs of an infestation. As late-season rain arrives, grubs that went deeper for moisture migrate upward to feed, causing catastrophic root damage. A simple September check can diagnose the problem before it is too late.

How to Test for Grub Worms

If brown or bare patches persist in your lawn this month, a quick test is essential. Grass that is merely dormant will green up with rain, but grass whose roots have been eaten will not recover.

First, grab a handful of discolored grass and tug. If the blades pull away easily from the soil, grubs may be the cause. For confirmation, use a spade to cut and peel back a U-shaped section of the affected turf. Search the soil for creamy-white, C-shaped grubs over half an inch long. A darker head and three pairs of front legs confirm they are chafer grubs.

Additional clues include a soft, spongy feel underfoot in damaged areas. You may also notice crows, skunks, or raccoons digging up the lawn as they hunt for the larvae.

Treating an Infestation with Nematodes

Once diagnosed, the recommended treatment is to use beneficial nematodes, a natural and safe biological control. The microscopic worms hunt and infect grubs with a bacteria that is harmless to humans, pets, and pollinators.

The species Heterorhabditis bacteriophora is most commonly used against grub worms. They are applied by mixing with water and watering them into the lawn. The soil must be kept moist for the nematodes to survive and move through the soil to find their prey.

For best results, apply the nematodes in the evening or on a cloudy day. Treat the discolored patch and a four-foot area around it. If dealing with several patches, treating the entire lawn is advised. After treatment, keep the soil moist to ensure the nematodes' effectiveness. Once the grubs are gone, the nematode population will naturally decline.

The Urgent September Timeline

Acting now is critical. The treatment is straightforward but time-sensitive. By mid-October, the larvae will burrow deeper into the ground, making them far harder to eradicate. Ignoring the problem risks permanent lawn damage, necessitating reseeding in the spring.

This five-minute check and subsequent treatment are vital components of September lawn care. Addressing a chafer grub infestation this month offers an excellent prognosis for lawn recovery.