How to manage grubs in the lawn
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Question: I think we have grubs in our lawn. There are dead patches that lift up very easily. I dug down with a trowel in those areas and found a few grubs. Is there a way I can control them that doesn’t involve using a chemical that could hurt my dogs?
Answer: Lawn grubs are the larval life stage of several different species of beetles. They feed on the roots of turf grass, causing it to develop brown patches that lift up like a piece of carpet. We have a few different species of grubs here in Western Pennsylvania, including Japanese beetles, northern masked chafers and Oriental beetles.
It’s difficult to tell the different species apart while the insect is in its immature larval stage, unless you’re prepared to look at the grubs under a magnifying glass or microscope and examine the hairs on their posteriors. Their damage is nearly identical, too.
The good news is that regardless of which types of grubs are currently damaging your lawn, nematodes are a natural and very effective solution. They’re easy to apply and safe to use around kids, pets and wildlife.
Nematodes are naturally occurring, microscopic roundworms that are found throughout the world. There are many different species; some are harmful to plants while others are not. The nematode species that act as biological controls for certain pest insects are not the same species that feed on plant roots. Instead, these beneficial nematodes live in the soil and enter pests and infect them with a deadly bacteria. The nematodes continue to reproduce within the body of the dead insect, multiplying until they exit the insect and search for a new host.
There are several different species of beneficial nematodes that can be purposefully introduced to garden environments to help control specific pests. Some of these species are mobile and they move through the soil, seeking out host insects. Other species are stationary and work best against insects that don’t move around too much in the soil profile. It’s this latter group of nematodes that’s best for use on lawn grubs. The species Heterorhabditis bacteriophora yields the highest level of lawn grub control.
Beneficial nematodes are living organisms that should be stored and applied with care. Typically kept under refrigeration until use and applied during cooler morning temperatures, nematodes come in a powder that’s mixed with water and applied to the lawn via a pump sprayer, watering can or hose end sprayer. The ground must be kept moist for a week or two after applying nematodes.
Because beneficial nematodes do not survive freezing temperatures, it’s best to apply them on a yearly basis for grub control. The best time to apply nematodes to the lawn is when the weather warms in the spring.
While you may find beneficial nematodes for sale at some local garden centers, most do not carry them because they require refrigeration. However, several mail order sources are a good alternative. Brands include NeemaSeek from Arbico Organics, Grub Away from Gardens Live or Parasitic Nematodes from Peaceful Valley Farm Supply .
In addition to controlling lawn grubs, there are other species of beneficial nematodes that are useful against different garden pests, too. Nematodes can also be used to control black vine weevil larvae, iris borers, caterpillars, corn earworms, cucumber beetle larvae, flea beetle larvae and many others.