Fall Grub Control and Prevention
Early fall marks a peak feeding time for grubs as they fatten up before winter. Once soil temperatures drop, grubs dig in, heading 4 to 8 inches below ground, where they’ll stay snug until spring. That means early fall – before temperatures tumble – is a key time to go after grubs, and as a result you can help prevent some of the most common lawn problems before they start.
In spring, when grubs emerge from soil, they don’t feed much, making spring grub control less effective. Lawn damage you see in spring actually occurred the previous fall, which makes fall control even more important. Stop grubs in autumn, and you can dramatically limit lawn damage. Try these tactics to curtail grub activity this fall.
Spiking for Grub Control
Spike sandals, typically sold for aerating lawns, don’t aerate very well. But a study by Colorado State University has shown that walking over grub-infested lawns repeatedly (three to five times) while wearing the sandals can cut grub populations in half – literally.
To control grubs most effectively, water the lawn the day before you plan to spike it. Applying about 1/4 to 1/2 inch of water will cause grubs to move higher in soil, closer to the soil surface – and your spikes. Watering will also help if the soil is dry by making it easier for spikes to penetrate.
Dethatching and Grub Prevention
A thatch layer protects grubs, shielding them from pesticide treatments. If you plan to treat for grubs and your lawn has a thatch layer greater than 3/4 of an inch, you might want to dethatch or core aerate prior to treating for grubs. Different grass types should be dethatched at different times of year. Learn the basics before taking action. Learn how to tell if you should dethatch, as well as when to dethatch and how to do it.
Grubs like moist soil and sparse, thin grass. Infrequent, deep lawn watering encourages deep-rooted, thick turf, which discourages grub activity. This irrigation practice also discourages adult beetles from laying eggs in your lawn – eggs that hatch into grubs.
Give your cool-season lawn a boost in the thickness department by overseeding in fall or spring. Thick lawns discourage grubs and adult beetles. Don’t overseed if you’re applying a weed control product containing a pre-emergent herbicide. Remember, overseeding is just one tool in your quest to maintain a lush, green lawn. For more tips from our garden expert, Lance Walheim, watch our video, "Steps to a Healthy, Weed-Free Lawn", below.
Keep a Clean Garden
Till the vegetable garden to expose grubs to the elements and predators. Hand-pick grubs you find as you’re planting. Drop them into soapy water, slice them in half with a trowel or toss them to the nearest bird for a snack. Learn more about fall garden clean-up.
Pesticides for Grub Control
For fall grub infestations, apply a pesticide that’s labeled for grub control and contains the active ingredient trichlorfon (Dylox) or carbaryl. (The active ingredient is listed on the front of the packaging.) Follow label directions carefully. Such pesticides often must be watered in after application; apply at least half an inch of water. Typically this means running a lawn sprinkler for as much as an hour. Use several straight-sided containers to measure and monitor sprinkler output to avoid creating pesticide runoff.
If soil is dry, water the lawn the day prior to pesticide application to encourage grubs to move toward the soil surface.
Nematodes are small, unsegmented worms that occur naturally in soil. The species Heterorhabditis bacteriophora provides good grub control. These nematodes search out white grubs, enter them, and basically liquefy their insides. Follow application instructions carefully, especially those related to soil temperature and moisture. Look for nematodes from companies that specialize in biological controls.
Timing is critical for fall grub treatments. Contact your local extension office to determine when grubs begin migrating to deeper soil in your region.
By following the instructions in this article, you will hopefully ward off any big grub problems next season. But be sure to observe your lawn for signs of grub activity. For more information, read Dealing With Lawn Grubs.