Controlling Grubs

By   October 8, 2015

Controlling grubs is a widespread problem and killing grubs is big business, so it’s not surprising that there have been many different ways invented. Some work better than others.

Let’s have a laugh first. There’s a company that created spikes that strap on to your shoes. As you walk across your lawn, the spikes are supposed to aerate the soil, controlling grubs at the same time. It sounds like a good idea, but when you’re working with a lawn any larger than a postage stamp, it would take Mrs. Smith’s entire tap dancing class weeks to get all of the grubs, and your lawn would be so torn up that there wouldn’t be much left.

If we eliminate the spike idea, that leaves 3 other management methods remaining. The first is a no-brainer. A good and healthy lawn can actually tolerate some grubs with no apparent effect. Maintain your lawn with a regular fertilization and liming program, mow it regularly and avoid cutting off more than 1/3 of the growth with each cutting, and keep it aerated. As you read through this website, you’ll notice that this is the same way to prevent weeds.

The next method is chemical. The most effective chemicals work only on newly hatched larvae, which are barely visible to the naked eye. So, waiting to apply insecticides until grubs have grown and are eating everything in site won’t be effective. If you know that you have grubs, it’s best to wait out the season until summer and attack when it will do some good.

Before we go on, let me express my personal opinion on insecticides. Most of them are poison, and most of the major chemical insecticides have been discovered to have some sort of effect on humans. Many that were once thought to be safe are now known to be hazardous and some are banned in the US. You might be familiar with the insecticides Dursban and Diazinon. Both were commonly used for lawn grubs but have now been restricted. If you need to use an insecticide, read the label carefully, follow the instructions, and use as little as possible.

This information is from the University of Rhode Island Landscape and Horticultural Program. They know a lot more about it than I do.

Dylox (trichlorfon) and Sevin (carbaryl). Dylox is a fast-acting material but is susceptible to alkaline hydrolysis. That means that it degrades in very hard or alkaline water or in a high pH soil very rapidly. One-half of the active ingredient will be degraded in 30 minutes at a pH of 9. Many public water supplies in Rhode Island are at pH 9 or higher. You also would not want to lime the lawn just before or after a Dylox treatment for the same reason. (If you are determined to attempt grub control in the spring – perhaps to reduce bird or mammal damage to the lawn, Dylox is one of the more effective materials available.)

Mach-2 (halofenozide) is an insect hormone mimic that is most effective against Japanese beetle grubs. It should be applied when beetles are flying (June 21-July 21). Low toxicity to non-target organisms. Soil half-life: 129 days. 

Imidacloprid (Trade Name: Merit) is an effective chemical treatment for grubs but, as noted above, it must be applied before eggs are laid. Treatments between April 1st and August 15th are generally effective.

The third major method of controlling grubs is biological.  Milky spore powder is a disease that kills Japanese beetle grubs but doesn’t seem to affect any other species. It’s not perfect, but it’s the easy way to go.  Once applied to the lawn, it spreads through infected beetles and remains active for years.  The drawbacks are that it takes a few years to build up the full effectiveness and if you spread insecticide and kill all of its host grubs, then the milky spore disease will die out too.