How to Get Rid of Grubs in the Lawn and Garden

If your lawn is dying, dried, and brown, the problem could be grubs. Beetle grubs – especially the larvae of Japanese beetles and their relatives in the Scarab family – feed on the roots of grasses and other plants.

A few grubs won’t create any problems, but past a certain population threshold, they can wreak havoc on even a healthy lawn. If you have a grub problem, you’ll probably need to treat it.

Best Grub Killer

In the past, the most common ways to kill beetle grubs have been insecticides, especially trichlorfon, dibenzoylhydrazine, and imidacloprid. However, these chemical poisons have other detrimental effects to the environment.

Trichlorfon is banned in the US in agricultural areas producing either food for humans, or feed for animals. It inhibits acetylcholinesterase, an enzyme that breaks down a neurotransmitter that’s important in all kinds of animals – humans included. Imidacloprid, which acts as an insect neurotoxin, is known to be very harmful to honeybees.

A safer approach is to use biopesticides. These products introduce other organisms that prey on or parasitize the grubs, but are not harmful to beneficial insects, beneficial soil bacteria, and other local organisms. Here are some of the products you can use to safely and effectively eliminate beetle grubs from your lawn.

Best Lawn Grub Killer

Beneficial Nematodes

One of the best ways to eliminate grubs specifically – without harming beneficial insects – is to introduce certain nematodes into the soil. Nematodes are microscopic roundworms, one of the most abundant animals on Earth.

This preparation contains three different species, one of which is a nematode called Heterorhabditis bacteriophora. This species has an endosymbiotic relationship with genus of bacteria called Phothorabdus. They live in the nematode’s digestive tract. The nematode pierces the outer skin of a beetle grub, and releases the bacteria into its body. These bacteria release toxins that cause fatal problems like apoptosis (cell death) of blood cells.

Within forty eight hours, the grub will die. The Photorhabdus bacteria then feed on the body of the dead grub, the process of which enables the nematode to also obtain nutrients from it. Along with grubs, the nematode and its endosymbionts will also attack some other pest species, notably the larvae of cabbage white butterflies and tobacco hornworms.

Along with H. bacteriophora, this product contains two other beneficial nematode species, Steinernema feltiae and Steinerma carpocapsae. Together, they help eliminate a range of common backyard insect pests.

Milky Spore Control

This product contains a bacteria called Paenobacillus popilliae (formerly known as Bacillus popilliae), which targets grubs — especially those of the Japanese beetle. The bacteria spores can be introduced to your soil with a simple one-time application, at a time of year when the grubs are most vulnerable to them. (Usually August.)

The grubs ingest the spores, which cause the “milky spore” disease, which kills them by interfering with normal blood circulation. The bacterial spores act as an effective population suppressant, becoming concentrated in the areas with the highest numbers of grubs. They’ll also persist in the soil for an average of two to ten years, helping to prevent a resurgence in the grub population. As a bonus, birds and other insect predators will often relocate the grubs to eat them, helping to further spread the spores to nearby areas.

How do you know if you have grubs in your lawn?

Beetle grubs damage lawns by feeding on grass roots, causing the plants to wilt and die. You can check for grubs by gently pulling up a small section of turf, using a trowel and wearing gloves. Grubs are visible as white c-shaped larvae. While a few can be beneficial, lawn damage can occur at a threshold of around ten grubs per square foot of sod.

What is the best time to treat for grubs?

Grubs that can kill your lawn are the larvae of various species of scarab beetles, especially Japanese beetles. These insects generally have a one year life cycle.

The adult beetles lay their eggs in the soil during the fall. In the spring, the grubs come out of dormancy, as the winter ends and the ground thaws out. At this point, they begin feeding on grass roots. In the summer, the grubs pupate and mature into adult beetles.

The eggs begin hatching in the late summer and fall, at which point the newborn larvae begin to feed on grass roots. In climates where the ground freezes and winter temperatures are low, they lie dormant until the spring.

As such, the best time to treat for grubs is in the early fall, at the peak of the egg hatching season. During winter, they will have burrowed deep, and are less susceptible to biopesticides like nematodes and bacteria, so you’ll want to treat your lawn well before the first hard freeze.

If you’re using milky spore bacteria to target beetle grubs, temperature is an important factor. The bacterial spores are sensitive to cold, and flourish the most in temperatures from around sixty to seventy degrees Fahrenheit. It may take longer to spread in cooler climates, like the Northeast and Upper Midwest, than in warmer southern climates.

How long does it take to kill grubs?

The amount of time it takes for the grubs to die can depend on what method you’re using to kill them. H. bacteriophora nematodes will kill a grub within 48 hours of piercing it and injecting it with bacteria. Milky spores can take a bit longer to kill the grub, which dies relatively slowly over the course of days as its circulatory system fails.

Does grub control kill other insects?

The answer to this question depends, at least in part, on which product you’re using, and what active ingredients it contains. Some formulations of beneficial nematodes contain both H. bacteriophora, which goes primarily after beetle grubs, and other nematodes that target different insect pests like moth larvae and fleas.

Milky spore disease bacteria specifically target the larvae of beetles in the scarab family, which includes Japanese beetles, the most common species that acts as a lawn pest in the United States. It does affect other beetle larvae, but not other types of insect pests.

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