Whitefringed Beetle
Graphognathus spp., Curculionidae, COLEOPTERA

DESCRIPTION

Adult - About 11 mm long, these black beetles are covered with dark gray and grayish- brown scales. They have two longitudinal stripes and a marginal band of white hairs. All whitefringed beetles are females and are incapable of flight.

Egg - The white, oval eggs are slightly less than 1 mm long and become pale yellow before hatching. They are covered with a sticky secretion which soon hardens.

Larva - The slightly curved, yellowish-white larvae are legless, have a light brown head, and measure up to 13 mm long.

Pupa - Approximately 13 mm long, the white pupae gradually darken as they mature.

BIOLOGY

Distribution - Native to South America, whitefringed beetles were first reported in this country in 1936 as pests of peanuts in Florida. They now occur from Florida to New jersey and westward to Missouri and eastern Texas. They were first found in North Carolina in 1942 and now occur in scattered localities throughout the state.

Host Plants - Whitefringed beetles infest at least 385 plant species. However, plants with taproots and smooth, broad leaves are most commonly damaged. Some important host plants include tobacco, peanut, corn, Irish potato, soybean, velvet bean, strawberry, okra, cowpea, sweet potato, bean, cotton, cauliflower, cabbage, cocklebur, and aster. Small grains can also be infested but their fibrous root systems are more tolerant to damage.

Damage - Whitefringed beetles are relatively innocuous foliage feeders which leave sawtooth cuts on outer edges of leaves. The larvae, however, are particularly destructive to taproots and underground stems. Infested plants turn yellow and, if severely injured, wilt and die. However, damage to N.C. tobacco is rarely of economic concern.

Life History - Whitefringed beetles usually overwinter as grubs although eggs may survive the winter in protected locations. After feeding on roots of tobacco throughout March, April, and May, the grubs burrow 5 to 15 cm into the soil and pupate for 13 days. By early July, most larvae have matured and entered the pupal stage. Adults emerge mainly in June or July. There are no males, and females produce eggs without mating. Eggs are usually deposited in clusters of 15 to 20 in the soil around the base of host plants. The actual number of eggs laid, however, depends on the type of host upon which the adults are feeding. Beetles raised on legumes or other broadleaf plants lay more eggs than those raised on grasses. Unless they overwinter, the eggs hatch 17 days after oviposition. The newly emerged larvae infest the roots of host plants until the onset of cold weather. One generation occurs each year.

CONTROL

Summer legumes are favorable to high beetle populations. Grasses, including corn and small grains are poor food for adults. Therefore, in known problem fields, tobacco should be rotated with grass crops to reduce pest populations.

In the past, quarantines were used to prevent the movement of infested soil and plant materials. At the present time, there is no insecticide registered for control of whitefringed beetles on tobacco. For the most up-to-date control information, contact the N.C. State Agricultural Extension Service.