Home lawn grub control

Home lawn grub control
Terry Davis, Entomology

This article was published in the April 18, 2008 Landscape Alert.

I have noticed dead patches in a number of yards along my way to and from Michigan State in the last two weeks. The rain we have had the last week or so will make it very clear where there are grubs actively feeding. Dead patches in lawns – especially lawns with sandy soil and areas that have a slope to them are likely places for grubs to be active now. If you see a dead patch, dig up a few shovelfuls of soil at the edge of the bare spot and look for 5/8-inch long, c-shaped grubs. These are more than likely the larvae of European chafer if they are found in non-irrigated turfgrass. European chafer can suddenly appear and devastate a lawn with no warning as the adults are active at dusk during late June and early July and can easily be missed as they move out of the soil and congregate in trees. Since they move back into the grass and lay eggs about 11:00 PM, the average person would never notice them unless they were carefully looking for them as the sun sets. Reports have also been coming in indicating a lot of grub activity in the Brighton, Cheboygan and Alpena areas. This is the first year we have heard about extensive damage occurring so far north in addition to the normal reports from the southern part of the Lower Peninsula.

Grub damage on turfgrass.

I went to several of the local lawn and garden centers in the Lansing area to see what kinds of products are available that specifically claim they will work for grub control. I noticed a considerable amount of overlap between brands and active ingredients and products carried by different distributors. Since curative grub products, preventive grub products and snake oil were all in the same areas of these stores, I suspect a large number of homeowners have bought and applied things that will not do what they thought they would. Several of the bags had claims on them that are a little inflated. The assumption that any product claiming to kill grubs will really work is wrong. It is also important to remember that healthy turf, especially if there is plenty of rain in the spring and fall can support a grub population of five grubs per square foot with no obvious turf damage. If the grub population is high, or if there is a history of damage in an area, it may be necessary to consider using chemicals for grub control.

There are basically two ways to approach grub control. Curative compounds should be applied when the grubs are present and active. Approaching grub control from the curative standpoint avoids unnecessary applications of chemical, but is not quite as effective as the preventive products. Preventive compounds must be applied at the time of egg hatching or when grubs are small to be effective. The first critical issue is to determine what active ingredient the product contains by looking at the label.

Do not use products containing only lambda-cyhalothrin, bifenthrin, deltamethrin, cyfluthrin and permethrin for grub control. Products containing these ingredients will not work for grub control when applied to the soil surface as the active compound will bind with organic material and will not move down to where the grubs are feeding. These products work well for turf feeding insects that live on the grass leaves or soil surface, but not for insects that feed on the roots. There are a few combination products that also include imidacloprid – read on to the next paragraph. I found a product called Triazicide (containing lambda-cyhalothrin) and another called Eight (containing permethrin) in rounds. I did find other products containing permethrin, but they were properly labeled as to controlling surface insects and not soil dwelling insects. Last year, I found two granular products that contained permethrin that indicated on the bag that they would work for grub control – they will not.

Products containing imidacloprid or halofenozide will not control grubs in the spring. They are preventive products and do not work well for large grubs.

Grubs as they would appear in the spring.

Although the bag often says apply anytime from May to Aug 15, it is highly recommended that these products be applied and irrigated into the soil during the first two weeks of July. If applied now, they will have little or no effect on the grubs currently in the lawn and furthermore, they will degrade by the end of July when the chemical works well for killing the newly hatched grubs. I specifically saw Scotts Grub-Ex, Bayer Advanced Season Long Grub Control w/Merit, Bayer Advanced Complete Insect Killer (which contains both imidacloprid and cyfluthrin), a product called Grub and Lawn Insect Control and Spectracide One Stop Once & Done that contained one of these active ingredients currently in stores. If applied in early July and watered into the ground, these products will give 90-100 percent grub control. They will cost $140 to $250 to treat an acre of turf.

What to use now
Any products that contains carbaryl (Sevin) or trichlorfon (Dylox) will work well when applied in the spring (from March to mid-May) or in the fall (September 1 to November 1). These are considered curative compounds as opposed to the preventive compounds mentioned above and will kill the grubs currently in the ground. It is necessary to irrigate after applying any curative product to get the chemical to the grubs. Run a lawn sprinkler for at least 60 minutes over treated areas (fill a bucket to ½-inch). It will take 10-14 days for the grubs to begin to die. One trichlorfon product called Bayer Advanced 24 Hour Grub Control states that it will kill grubs in 24 hours. However, I doubt that any of the insecticides will kill grubs in the soil in much less than five days unless there is rain and very warm temperatures. Do not apply any curative compound after May 15 as the grubs stop feeding in late May. These “curative” compounds will typically give 65-85 percent control of grubs and will cost $150 to $303 to treat an acre.

In summary
Check the bag to determine what active ingredient the product contains.

Do not use products containing only lambda-cyhalothin, bifenthrin, deltamethrin, cyfluthrin or permethrin for any phase of grub control.

Do not use preventive compounds such as halfenozide or imidacloprid now. Use them during the first two weeks of July to control grubs that would be damaging turf in the fall.

To kill grubs in the spring use carbaryl or trichlorfon and irrigate.

Always wear rubber gloves and rubber boots when applying insecticides to turfgrass. Make sure to irrigate the lawn with at least ½-inch of water and allow the grass to dry before allowing anyone (or pets) into the treated area.

A short list of products now being sold for grub control as of April 18

Sevin-Lawn Insect Granules (20 lb bag) Various manufacturers carbaryl 2.0% 9 lb/1000 ft2 Apply in spring or fall to active grubs.	Grub & Lawn Insect Control (15 lb bag) Made by DowAgro halofenozide 1.5% 3 lbs/1000 ft2 Apply in early July.
24 hr Grub Killer Plus (15 lb bag) Made by Bayer Advanced trichlorfon 6.2% 3 lbs/1000 ft2 Apply in spring or fall to active grubs.	Grub and Lawn Insect Control (15 lb bag) Packaged by Meiers halofenozide 1.5% 3 lbs/1000 ft2 Apply in early July.
Complete Insect Killer (10 lb bag) Made by Bayer Advanced cyfluthrin 0.05% and imidacloprid 0.15% 3 lbs/1000 ft2 Apply in early July.	Eight (ready to spray – lists white grubs on bottle) made by Bonide permethrin liquid spray for hose applicator Will not kill grubs at any rate.
GrubEx (14.35 lb bag) Made by Scotts imidacloprid 0.2% 2.87 lb/1000 ft2 Apply in early July.	Triazicide Once and Done Insect Killer Granules(10 lb bag) Made by Spectracide lambda cyhalothrin 0.1% Will not kill grubs at any rate.
Season Long Grub Control (14.35 lb bag) Made by Bayer Advanced imidacloprid 0.2% 2.87 lb/1000 ft2 Apply in early July.