In late summer, grubs make up a dominant food source for skunks, raccoons, and opossums. Even crows and deer will disturb the ground surface in search of grubs and other buried food sources. These predators scour the lawn with their noses to pick up the grub’s scent and once found, they begin digging, leading to lawn damages.
Entire lawns can be damaged by mammals scavenging for grubs. The difference between squirrels hiding nuts and mammals digging up grubs is that squirrels will bury their food thus, repairing the damage.
The Grub Life Cycle
Female grubs lay their eggs in clutches, which hatch in the late summer. When the grubs begin to feed on the grass roots, they are in compact groups, of up to 12 per square foot or more from one female. Numerous females laying eggs across one lawn create a large area of ample feeding opportunities.
Grubs feed on grass roots twice per year. The summer brood is laid in clusters, which result in more concentrated damage (from predators and the grubs themselves), compared with the spring when they are more spread out.
How to Control the Pests
One organic pest control method is to use beneficial nematodes. Nematodes enter a live grub and then multiply until they finally burst out of the dead bodies.
The number of nematodes inside a single grub ranges from 5,000 to 10,000. Then the nematodes leave to find other insects, starting the whole cycle all over again. Paybacks!
Nematodes will not kill off the grubs overnight, so predators can still dig up the lawn while the grubs are dying off. This is true even for chemical control methods.
Nematode Life Cycle
Chemical control methods work by applying the liquid or granular chemical product to the lawn or ground surface. The turfgrass takes up the insecticide into its vascular system, effectively making the plant the poison.
Then the grubs eat the grass roots, ingesting the poison which kills of the grubs in about 10-14 days. During this period, when scavenging mammals eat the grubs, they are also ingesting the poison, thus poisoning the food chain and leading to bioaccumulation of toxins in the environment and a torn up lawn.
Grub damage to turfgrass looks similar to fungal diseases like “dollar spot” and ‘’brown patch”, which show up around the same time of the year. The difference is that grub damage separates the grass root from the stem so that the grass pulls up without any effort.
