I recently wrote a post on those awful summer pests, Japanese Beetles. As I mentioned, these iridescent little critters come from our friends the white grub worms (as do other pesky beetles like the June Bug), and Japanese Beetles are just as annoying in adolescence as they are in adulthood.
While I won’t go into the whole gamut of their life cycle again (check out my Japanese Beetle post for those details), I will provide you with a more thorough description of their appearance and, most importantly, how to treat them. Keep in mind as you read this, however, that treating grub worms will not eliminate beetle problems later – both require treatment every year to keep your yard and garden looking spiffy.
Grub worms have a white segmented body with a brown head and six scraggly legs at the front of the body. Their backside is usually a dark brown to black under stretched skin and looks a lot like a reservoir of fecal matter, often bulging from their feeding indulgences.
Noting damage caused by grubs is pretty easy. They feed on turf roots, so grass they are feeding on turns brown and dies. Main feeding times are right after hatching from eggs in August and September, for about 3-4 weeks before they hibernate for the winter. After spring temperatures start to rise, they will begin feeding on turf roots again for a few weeks as they build up strength to morph into beetles.
If you have browning spots in your lawn, check for grubs by pulling up the grass. If the turf comes up like a piece of carpet, then you likely have a grub problem (you’ll probably even see a few when you lift the grass up).
Another sure sign, if you live near a wooded area, is that your yard will suddenly have holes overnight. This is from creatures like skunks, raccoons, armadillos, birds and other animals that love the juicy taste of these nasty little worms.
If you aren’t seeing a lot of damage, but know that you had a serious Japanese Beetle problem last summer, then you can still check to see if their larva are around by digging. Dig one square foot out of your lawn about 4 inches deep. One or two grubs in that space aren’t really cause for concern or treatment. However, if you’re seeing 4-7 grubs or more in a square foot of soil, you’ve probably got a problem on your hands.
Living in an area with a large population of Japanese Beetles in the past few years, it stands to reason that those of us in the Midwest (Oklahoma, Missouri, Arkansas, etc.) likely have grubs in our soil. One step you can take is to apply insecticides regardless of whether you know you have a problem or not. It’s sort of like having insurance on your turf – your treating the possibility of a problem before it actually becomes a problem.
Regardless of whether you’re treating the lawn for preventative maintenance or know that you have a grub problem, the best time to treat for them is during late summer and early fall, when they are feeding the most. They get too deep in the soil during winter hibernation and are so large and on the verge of becoming beetles that treatment is virtually ineffective during winter and spring months. You want the grubs to have hatched (around August) and to be young and venerable.
As mentioned, insecticides are effective at treating grubs. Keep in mind, however, that they only last 2-3 weeks and may require additional applications. These insecticides are easy enough to find at your local hardware or lawn care store – they will be clearly marked for grub treatment. They all seem to work on an equal plain.
If you prefer to use a natural grub treatment, there are some effective options available. Milky spores, available at your local lawn care store, are one option. You simply apply the spores to the lawn and the grubs ingest them while feeding. These grubs die and spread more spores, killing off other grubs.
Neem oil is a natural pesticide, mixed with water and applied to the lawn. It inhibits the egg laying process in regard to Japanese Beetles, and also inhibits the hatching, growth and feeding process of the grubs already established.
You can also add nematodes to your lawn – a small worm that releases bacteria into the soil that won’t affect your plants or turf, but kills grubs. These worms are so small that they come in a liquid form that is typically mixed with water and sprayed on your lawn.
Another alternative is to take my approach. I’ve never had a really bad infestation of grub worms (knock on wood), so typically as I’m working in my vegetable garden or flower bed I come across a few of them… and I simply take my hand shovel and cut the little buggers in half. Simple, yet effective (and admittedly quite disgusting).