- Pest Type: Insect
- Crops Affected: Wheat, Soybeans, Corn, Peanuts
- Scientific Name: Phyllophaga spp.
- Pest Order: Coleoptera
Eggs are pearly white and oval, and are laid from one to several inches deep in the soil. Larvae are white, C-shaped, with 3 pair of prominent thoracic legs, just behind a brown head. Fully developed larvae or white grubs are 19-38 mm long. Pupae are about the same size as the larvae and are creamy white to yellowish to brown. The adults, reddish-brown to brownish-black beetles, are also 19-38 mm long, and are referred to as "June bugs", "June beetles", "May beetles", "daw bugs", or "masked chafers".
Larval root feeding can cause severe damage or death of young corn seedlings. Pruned roots cause rolled and/or discolored (yellow and purple) leaves. Plants are stunted and may die, even after the corn is 1-2 feet tall. Corn fields injured by white grubs were generally in sod, cover crop, set-aside fallow, or in rarer cases, soybeans the previous season.
Damage from this white grubs occurs in fall and spring. Grubs in the soil feed on roots. This root feeding by larvae can cause damage, generally stunting, or even death to young seedlings. Adults may feed on foliage, but that is rarely of economic importance. Fields injured by white grubs were generally in sod, a cover crop, or set-aside fallow the previous season.
Some white grubs are part of a 3 year life cycle. For those, the overwintering adults emerge from the soil in May and June, and are active for about 2 months. They mate and the females lay eggs, generally in soil/thatch areas with grassy weeds or sod. Those eggs hatch in about 2 weeks and the young larvae feed on available plant roots. The larvae remain in the soil feeding for 2-3 years. In the fall of the last year of the life cycle they pupate. Adults emerge and remain in the soil overwinter. Other grubs have 1 year life cycles, with adults emerging in June to mate, eggs are laid in the soil throughout June and July, the eggs hatch and larvae feed on roots until fall. Those larvae overwinter and pupate the following spring.
Grubs can generally be seen when preparing fields for seeding. Several cultural practices help reduce white grub populations. For example, late-summer or fall plowing may expose larvae, pupae and adults to predaceous birds. Crop rotation to less susceptible crops such as clovers or alfalfa also helps. There are no outstanding rescue treatments for grubs. If a field is replanted due to white grub damage and the grubs are still present and active, use a soil insecticide and/or seed treatment labeled for control of white grubs. Contact local advisers regarding recommended controls in your area.
Many species of white grubs are found throughout North America. During the summer, these beetles are often seen flying around lights at night. White grubs attack the roots of many cultivated crops.