White Grub, Phyllophaga spp., Coleoptera: Scarabaeidae

Description

White grub is generally a term given to the larvae stage of a group of over 200 species of scarab beetles. Adult descriptions vary greatly but the most common is referred to as the May beetle. These adults are commonly found at lights during late spring and summer nights. May beetles are about one inch long and tan to dark brown in color. Larvae are cream colored scarabs with a tan head capsule and dark internal markings on the end of the abdomen (Photo 5). Six true legs are easily seen on the thorax.

Distribution, damage and impact

White grubs occur in the soil of grain sorghum fields throughout Arkansas. Damage may occur when the grubs feed on underground roots. However, in recent surveys the impact of white grub has been minimal. Fields recently converted from pastures are most susceptible.

Life History

The biology of white grubs vary greatly due to the many different species. In general, adults emerge in the spring, mate and deposit eggs in a cell below the soil line. Larvae hatch and can complete their development through the summer and fall or may take two or more years to mature. Pupation occurs in the soil.

Management

In south Arkansas avoidance of recently plowed grassy fields including pastures will reduce the attractiveness of the field to adult beetles. Rotation of grain sorghum with broadleaf crops, esp. soybean, will reduce the likelihood of damage. Use of treated seed or soil insecticides applied at planting may reduce larval populations but is not likely to be economically effective if directed only at the white grub.

Insecticide recommendations for white grub on grain sorghum

See Table 1 for insecticide recommendations current at time of publishing. Current updated recommendations can be found in the Cooperative Extension Service publication MP-144 and on the world wide web at WWW.cdms.net/manuf/default.asp. Always follow instructions on pesticide labels.