For many years now, White Grubs in our lawn have caused sleepless nights for those of us that strive for a beautiful carpet of green around our homes. These pesky little creatures set up shop in our lawn and proceed to chew the roots off of our grass plants.
When you have more than 5 - 9 grubs per sq. ft., their feeding results in brown patches of grass that can be easily pulled out by hand. You may also find that skunks and raccoons are digging in your lawn, searching for their favourite food, White Grubs. We’ll pass on judging their taste and eating habits for now. It is usually much easier to eliminate the food source, than it is to deter a predator like a hungry skunk or raccoon from your yard. If you do want to deter them, you need to know first which predator you are dealing with and then find an acceptable treatment for your specific situation. (Usually skunks will dig a small, circular hole while raccoons tend to rip or roll up the lawn).
Though usually spotted in the spring, the Grub damage is most often done in the fall. This is why the mid-summer (late July/early August) treatments are most effective, you get the Grubs “before” they begin to feed. Maintaining a healthy lawn can minimize the effect of Grubs. By having deep, thick roots grass can withstand damage more easily than if they are shallow and weak. With the Province of Ontario banning most pesticides, we are left with Nematodes as the only weapon in our arsenal to fight these invaders.
What is a Grub?
Grubs are the larvae of either the June beetle or European Chafer and ‘occasionally’ the Japanese beetle, though it is possible to have all three types in your lawn. Each type of Grub has its own life cycle, from 1 to 3 years (see the link below for more detail).
What is a Nematode?
Nematodes are the most numerous multi-cellular animals on earth. A handful of soil will contain thousands of the microscopic worms, many of them parasites of insects, plants or animals. Free-living species are abundant, including nematodes that feed on bacteria, fungi, and other nematodes, yet the vast majority of species encountered are poorly understood biologically. There are nearly 20,000 described species classified in the phylum Nemata.
Nematodes are structurally simple organisms. Adult nematodes are comprised of approximately 1,000 somatic cells, and potentially hundreds of cells associated with the reproductive system. Nematodes have been characterized as a tube within a tube. Nematodes possess digestive, nervous, excretory, and reproductive systems, but lack a discrete circulatory or respiratory system. In size they range from 0.3 mm to over 8 meters.
How does a Nematode work?
Nematodes migrate through the soil finding insect larvae by detecting either a slight increase in temperature or release of methane gas. The infective juvenile nematodes, by entering the larvae and releasing symbiotic bacteria, kill the host within days. The nematodes feed on the bacteria and the decomposed host tissue where they reproduce until numbers drive them out to find a new host.
NOTE: It is recommended that you keep your Nematodes refrigerated until just before use. Then follow the directions for preparing and applying.
For more detailed information about grubs, their habits and life cycles you can visit www.uoguelph.ca/pdc/Factsheets/Insects/grub.htm.