There are a number of different control programs for reducing white grub damage in turfgrasses and using the principles of integrated pest management (IPM) is the most prudent and efficacious way to deal with preventing damage and mitigating any current damage by white grubs.
Natural control options
- The occurrence of white grub damage is often sporadic over a given area and over a given time period. In most cases, natural control will keep this pest under damaging threshold levels.
- As a homeowner, you can increase natural control by limiting any insecticide applications and promoting a diverse plant community that will attract parasitoids and predatory insects. Be tolerant of skunks if they are present in your area. They eat grubs and aerate lawn naturally with their digging. You may need to do some repair with overseeding.
- Maryland soils contain abundant levels of microbial pathogens and entomopathogenic nematodes that will increase white grub control.
- Weather conditions can also impact white grub survival and during drought years populations of these insects will decline. Irrigated lawns have a higher incidence of grub damage because adult beetles need moist soil for their eggs to be viable.
- When all of these factors are combined they play an important role in keeping white grub activity below damage threshold levels.
Biological control options
- A number of biological control products are available for use by homeowners. Control varies and typically excellent control rarely occurs with these products. Numerous factors such as rainfall, temperature, to shelf life of the biological control products affect results.
- Insect parasitoid nematodes (entomopathogenic nematodes) are one of the better biological controls for white grubs. Heterorhabditis bacteriophora nematodes have provided good white grub control. These nematodes have a short shelf life and need to be applied within the season they are purchased. The earlier they are applied to the purchase date the better the control. These nematodes can be applied using a sprayer and diluted at 1.5 to 2 gallons of water per 1,000 square feet. Sunlight and desiccation can reduce their performance. Applying them in late afternoon and watering them in right after application and for several days after application will improve the efficacy of these nematodes.
- Update 2020 - A new species of nematodes, Steinernema scarabaei, has been showing promising results in research studies. This species has a longer shelf life and refrigeration is not necessary, although it is recommended to store it at temperatures of 40-60 degrees F. They are available to professional lawn care companies.
- Various bacterial and fungal diseases of white grubs that are present in Maryland soils have been developed as biological control agents and include milky spore disease (Phaenobacillus), green fungus (Metarrhizium), and white fungus (Beauveria). These microbial based insecticides have not provided consistent levels of control in various university field trials.
- Bacillus thuringiensis (Bt) is a bacteria-based product in which a protein endotoxin is produced within the insect gut. This endotoxin reduces insect feeding and results in insect death. Recently a new strain of Bt was introduced for white grub control and is commercially available as GrubGONE (Bt ‘galleriae’). Based on a number of university studies moderate control levels (70-80%) for Japanese beetle and masked chafer grubs occurred when applied to early instar grubs (July to early August). This product may be difficult to find on the market.
- Insecticides that are labeled for white grub control have provided excellent control when applied properly.
- Only treat turf areas that are damaged by grubs and not the entire lawn.
- Imidacloprid (Merit and other numerous trade names), has been widely used for grub control since 1994. But, recent concern on the impact that these products have on insect pollinators resulted in the passage of the Pollinator Protection Act of 2016 by the Maryland General Assembly. The law went into effect on January 1, 2018 and restricts the sales and use of neonicotinoid pesticides. Only farmers and certified pesticide applicators (or people working under their supervision) can apply neonicotinoid pesticides outdoors.
- A control choice that is relatively safe to apply and provides excellent control is Acelepryn (Chlorantraniliprole) which is found in GrubEx (active ingredients can change periodically so check the product label). In addition to excellent white grub control, surface feeding insects such as sod webworms and cutworms are also controlled. This insecticide has low toxicity to vertebrates and has shown no adverse effects on beneficial insects. Acelepryn has a broad application window (May – September).
- Decent soil moisture is needed when applying acelepryn and needs to be watered in. Check product label.