Management tips for common grubs

Asiatic garden beetle; European chafer; green June beetle; Japanese beetle; typical masked chafer; oriental beetle; Typical May/June beetle, black turfgrass ataenius. (Photo: Ohio State University Extension)

Grubs can destroy turfgrass roots, cause the lawn to become spongy and make the turf roll back like a piece of carpet. Before beginning treatment to combat this insect and its damage, lawn care operators (LCOs) need to identify the grub species to ensure the best results.

Properly identifying grubs is important because of the differences in the adult flight, mating, egg laying and hatching periods across species.

That information determines the timing of the insecticide application or the control method used, says Edwin Afful, Ph.D., insecticides product development manager for FMC.

“Understanding the biology and insect life cycle is essential to identifying the life stage of the insects and to help understand how best to start scouting and deciding on the appropriate control option,” Afful says.

Common grub species

Grubs have a C-shaped body with three pairs of legs immediately behind their heads. The entire body measures ¼ to 1 inch in length, depending on the species and development stage, Afful says. Depending on the geographic location, there are close to a dozen different beetle species with larval stages that can feed on turfgrass roots.

The most common grubs that LCOs face include the Japanese beetle (Popillia japonica), European chafer (Amphimallon majale), masked chafer (Cyclocephala spp.) and oriental beetle (Anomala orientalis). Others include the May/June beetle, Asiatic garden beetle and black turfgrass ataenius.

While the larval stage of many of these species are nearly indistinguishable from one another, the arrangement of hairs on the tip of the abdomen (raster) can help LCOs better identify them as they mature, says Matt Giese, technical services manager for Syngenta.

“This raster pattern widely varies but is a reliable method to identify mature white grubs,” Giese says. (See the different patterns for each in the images below.)

How to control

Common grub management methods include chemical, biological or microbial controls. Treatments that are preventive and target newly hatched or small larvae are the most effective, Giese says.

The application timing for white grub products varies based on their residual lengths and should start before peak adult flight occurs. Operators can check with their local Extension office for information on adult beetle flight occurrences.

“If peak adult flight occurs in early July, for example, treatments should be made prior to this date; potentially up to 45 days before depending on the treatment choice,” Giese says.

Curative treatments usually are applied when grubs are actively feeding and causing damage during the spring or fall.

“If significant lawn damage is taking place or animals are digging in the area where they are active, the grubs may be in their third instar, meaning you’ll need to apply an insecticide that will get to the grub larvae in the soil,” Afful says. “Most of the curative insecticides require watering after the application to maximize their control.”

For biological control of white grubs, insect parasitoid nematodes and heterorhabditis bacteriophora nematodes are good options.

“These nematodes have a short shelf life and need to be applied within the season they are purchased,” Afful says. “The earlier they are applied to the purchase date, the better the control.”

Bacterial and fungal diseases of white grubs present in soils serve as biological control agents, Afful says. Examples include milky spore disease, green fungus and white fungus.

Several treatment options available for grubs will control many of these species as a preventive application.

“So, sequential applications for multiple species are not necessary,” Giese says.