Controlling White Grub in Turfgrasses

Jun 04 2018

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The term grub refers to the larvae of various types of scarab beetles, and the most common types of white grubs include the larvae of European chafer, June beetle and Japanese beetle1. These are destructive turfgrass insects that, if not controlled, can cause significant damage to turf, such as wilting and browning. Use this insect identification guide to learn more about how to control these common golf course pests.

White Grub Identification

All species of white grubs have soft, wrinkly, C-shaped bodies that are either white or yellowish in colour, with tan or brown-coloured heads and six spiny legs. Depending on the grub species, mature grubs can range in size from 2 cm to 4 cm, though they are much smaller when they first hatch (around 3 to 4 mm long)1.

If you notice brown grass or areas that feel soft or spongy when walked on, this can indicate a white grub infestation. To determine whether white grubs are present in turfgrass, use a golf course cup-cutter or a sturdy knife to cut a core or wedge from the sod, about 3 inches deep2. Carefully break apart the soil and examine it for the presence of white grubs.

A few white grubs may not be an issue, but 5 to 10 per square foot indicates an infestation. Monitoring white grubs in turfgrass should be done in the spring and fall, when infestations and damage will be at their peak3.

Damage Potential

Grubs feed on the roots of many plants, but prefer to feed on turfgrasses3. They can cause extensive damage by destroying the root system of turfgrasses, leading to sections of wilting and browning. The turf may eventually die and will lift from the soil, as the roots are no longer present to keep the turf down. Secondary damage can be caused by animals such as skunks, raccoons and birds pulling back the turfgrass to search for grubs to eat.

Most damage occurs in the spring and fall when grubs feed near the surface and grow rapidly in size.

Control Tips

Keeping the turf well maintained is an important first step in preventing white grub damage. Well-watered, healthy turf will have more roots, which will better withstand any damage. Too much water, however, can actually encourage eggs to hatch and bring the grubs to the surface to feed. It’s best to water deeply, but infrequently, to balance soil moisture. Aeration and fertilizer use can also help boost the turf’s resistance to white grub2.

Some biological control options are available, such as microbials and parasitic nematodes, which attack and kill white grubs. These are commonly used in early fall, but tend to be more expensive than chemical control methods and can be more varied in efficacy2.

 Chemical insecticides can provide affordable, effective control of white grubs in golf course turfgrass. These can be used as preventative measures, control methods for early infestation, or rescue options for heavily infested turfgrass. For best results, refer to the manufacturer’s recommendations for application and timing.

Before spraying, you’ll want to ensure you know the species of white grub you’re dealing with. Refer to a species identification guide, like this one from Ohio State University, to help you select the most effective control option possible.

Once you know the species, it’s time to evaluate your pest management options. Our broad-spectrum turfgrass insecticides offer effective control of white grubs to keep golf courses looking their best. Click here to see our solutions.

References
1“Grubs in Lawns.” Ontario Ministry of Agriculture, Food and Rural Affairs. Online. 8 May 2018. https://bit.ly/2ryecUR
2Richmond, Douglas S. “Turfgrass Insects: Managing White Grubs in Turfgrass.” Purdue University: Extension Entomology. Online. 8 May 2018. https://bit.ly/2aRU1c2
3“White Grubs.” Government of Canada: Pest Control Tips. Online. 8 May 2018. https://bit.ly/2zMj5zm