Lesser cornstalk borer is an important pest in the Southeastern and Southwestern growing areas. It is usually a problem during hot, dry weather and is more often a problem on coarse, sandy soils than on heavier soils. Lesser cornstalk borer larvae will feed on underground pegs and pods in addition to any part of the plant above ground that contacts the soil surface.
Burrower bugs can be hard to identify in the field and an infestation is often not detected until harvest. Burrower bugs have a black-to-brown body, small red eyes on a small-sized head. The upper wings of burrower bugs are shiny and semi-hardened with the membranous tip overlapping. Its legs are spiny, and strong chewing mouthparts are visible with a hand lens. Burrower bug is closely related to stink bugs.
Three-cornered alfalfa hoppers are light green and wedgeshaped. They stand about 1/4 inch high and are about 1/4 inch long. Both adults and nymphs have piercing mouthparts and feed by penetrating the stem and sucking plant juices. They tend to feed in a circular fashion around a stem, making feeding punctures as they go (see photo). The damaged area typically swells and above ground root growth may occur. On peanuts, feeding may occur on limbs, leaf petioles or pegs.
Leafhoppers are small wedge-shaped, green, brown or black insects about 1/8 to 1/4 inch in length. Leafhoppers insert their beak into the midrib on the lower side of peanut leaves and suck plant juices. Leaves turn yellow from the point where the feeding has occured to the tip of the leaf and may die in severe cases. This damage is often referred to as “hopper burn.”
In peanuts, these two closely related insects are usually referred to as corn earworms, but tobacco budworms are often a significant percentage of the total population. Larvae of both species feed on peanut foliage and are very similar in appearance. The corn earworm moth (above) and the tobacco budworm moth are often seen in peanut fields and may indicate that larvae will soon follow.
Southern corn rootworms are most often found on heavy soils that are poorly drained. During extremely wet weather, they may become a problem even on sandy soils. This pest is a subterranean feeder. It may feed on the roots of peanut plants to some extent, but its most important damage is due to peg and pod feeding. Usually the holes cut into pegs and pods will be almost a tiny drill bit. In contrast to lesser cornstalk borer feeding, there is no webbing associated with this pest.
Fall armyworms are one of several foliage feeders that may attack peanuts. In some years, they can be the predominant foliage feeder. Caterpillars, gray, light brown or mottled green in color, reach approximately 1 1/2 inches in length when fully grown and have a prominant inverted “Y” on their head. When abundant, fall armyworms can strip plants of foliage and “march” to other host plants. Female moths lay egg masses of about 150 each and cover them with scales from their body.