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Photo Credit: ©2001 Buglady Consulting

One white grub in your lawn does not make a problem. It’s when you have high numbers that you should be concerned.

First, do you even need to treat? When grub populations are low (less than six white grubs per square foot), treatment isn’t usually needed. Your lawn can outgrow the pest at this level. It’s when you get populations of 10 or more per square foot that you need to treat your lawn.

One method is to try cultural controls. These are physical things you can do in your landscape to help prevent white grub infestations from occurring. Certain species of beetles (the adult stage of white grubs) prefer specific plants. This is very true with Japanese beetles – pests that love to feed on roses, Japanese maples and lindens. So growing these plants in an area where white grubs have been a problem in turf wouldn’t be such a great idea. The adults would only be attracted to these plants, and it’s a quick flight down to the lawn to lay their eggs.

Another way to help manage grub populations is through water management. Almost all white grub species eggs need moisture to hatch, and the youngest grubs are very susceptible to desiccation. If areas of your lawn can handle reduced watering, don’t irrigate in July and early August, when white grub eggs and young grubs are present. This’ll cause them to dry up. In May, as well as in August through September, you can water and fertilize moderately because the grass can outgrow the grub feeding damage.

There are also some naturally occurring controls Mother Nature has provided for these pesky grubs. Several parasitic wasps attack white grubs and may help reduce populations in certain areas. The problem with this method is you have to wait for these beneficials to build up their populations, which can take two to three years. Most people aren’t willing to wait that long, so insecticides are applied and the beneficials are killed off.