Grub worms are not a single species, but rather the larval form of various beetles. This includes, Japanese beetles, June bugs, and billbugs. While they may be harmless as adults, any variety of grub worm can wreak havoc on your lawn.
A small amount of grub worms in your soil is fairly normal, and may not be any cause for concern. But as their numbers increase, they can become a true threat to both the health and beauty of your landscape.
Thriving on the roots of your grass as their primary food source, these tiny white squirmers can cause bothersome brown patches in your lawn. They are most active in the summer, which is something you can use to your advantage when we discuss treatment methods.
So how do you know whether your lawn is at risk? Or if you’ve already got a few brown spots, how do you know whether grub worms are the culprit? After all, half the battle with proper lawn care is knowing exactly what you’re dealing with, so you can execute the most effective solution. For more great advice on keeping your lawn healthy, check out How to Keep Your Lawn Healthy and Fertilized in the Summertime.
If you suspect you’re dealing with grub worms, here is how to find out for sure. Remove one square foot of sod from your lawn, about 3 inches deep, and inspect the soil. If you spot 5 or more grubs within that amount of yard space, you’ve gotten into the danger zone.
So what to do?? While there is no instant solution to a grub worm infestation, there are still several good methods to explore. Let’s take a look at some remedies- both natural and commercial- that have been proven effective.
Beat ‘Em with Bacteria
Milky spore (bacillus popiliae) is available at home and garden stores, and is harmless to your lawn. The spores cause a bacterial environment known as milky disease, which attacks the grub worms.
Milky spore takes 1 to 3 weeks before it begins affecting grub worms. They great thing about this method is that, within a few years, the subterranean bacterial colony will have spread sufficiently to make your soil a permanently hostile environment for these pests.
Beneficial nematodes are microscopic parasites that attack the grub worms’ bodies. Just like the spores, they are completely harmless to your yard. Yet, as they release bacteria into their host worm, they wreak havoc that eventually leads to death.
You’ll want to be sure you purchase beneficial nematodes from a trusty source. As live organisms, they need to be handled correctly during shipment, to maintain their health and overall quality.
Beat ‘Em with Heat
As we mentioned before, grub worms are most active in the summertime. That is because this is when beetles lay their eggs, and it only takes 2 weeks for them to hatch. Fortunately, drought is a great way to kill off a fresh invasion of these hungry little lawn hazards.
If you’re facing a summer drought, and are willing to lay off the lawn irrigation for 3-4 weeks, the results will be deadly for the grub worms in your soil. And don’t worry too much about your beautiful green blades going yellow. An otherwise healthy lawn will quickly brighten back up as soon as you resume a regular watering schedule.
There are several products on the market that can effectively address grub worms in your soil. The two types are preventives- as in, preventative measures, and curatives- as in, attacking an infestation that is already established and growing.
Preventives stop grub worms from taking hold in your yard’s soil in the first place. Much like milk spore, they create an environment that is hostile for grub worms, so they’re a great choice if you want to avoid an infestation altogether. Products like Merit and Mach 2 are known to demonstrate high efficacy as preventives.
Curatives are effective in killing young larvae, but won’t help rid your yard of worms that have matured into pupae in their developmental stage. They are best applied in late summer or early autumn. Products containing the chemical trichorfon are considered highly successful.
While a few grub worms are nothing to worry about, you want to be prepared if your lawn starts showing tell-tale brown spots that indicate a harmful infestation. There are several natural remedies, including drought and commercial bacteria. Additionally, you can purchase both preventive and curative products from your local home and garden store.
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