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Insecticide ID Guide



LESSER CORNSTALK BORER

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.

FALL ARMYWORM
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.
SOUTHERN CORN ROOTWORM DAMAGE
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.

 

CORN EARWORM/TOBACCO BUDWORM
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.

 

LEAFHOPPERS
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.”
 

THRIPS
Thrips are tiny, slender insects about 1/32 inch in length. They vary in color from yellow to black. Adults will have wings and may fly when disturbed. Thrips feeding often results in stunted peanut plants with leaves that are scarred and “possum-eared” (leaf edges are turned down). Thrips also transmit the virus that causes tomato spotted wilt in peanuts.

 

THREECORNERED ALFALFA HOPPERS
Threecornered alfalfa hoppers are light green and wedge-shaped. 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. The damaged area typically swells and above ground root growth may occur. On peanuts, feeding may occur on limbs, leaf petioles or pegs.

SPIDER MITES
Spider mites are not really insects, but are closely related to insects. Although spider mites are small, they can be seen with the naked eye, especially if they are moving. Spider mites feed on peanuts by sucking plant juices from the undersides of the leaves. This feeding, which usually begins near the midribs of the leaves, results in a speckling of the upper surfaces of the leaves. As infestations become more severe, leaves turn yellow and die. Heavy infestations are characterized by visible webbing.


WIREWORMS
Wireworms are the immature stages of “click” beetles. There are many species that damage peanut plants by feeding on the underground parts. The “worm” stage is always found in the soil, but finding them may be difficult. Wireworms may be noticed during land preparation, but usually infestations are often first noticed as the result of damage to pods. Depending on size, wireworm damage can vary from small clean holes to large irregular holes.


BENEFICIAL INSECTS
Insect pests are vulnerable to a vast array of natural enemies. Control of insect pests by biological agents is the first line of defense in a sound insect control strategy. Physically moving beneficial organisms into a peanut field is not practical. However, avoidance of practices that unnecessarily reduce beneficials will allow them to work to their maximum potential.

 

VELVETBEAN CATERPILLAR
This insect is one of several caterpillars that often feed on peanut foliage in the southern peanut-producing regions. Although easily controlled with insecticides, this insect is a voracious feeder and can do a great deal of damage in only a few days if not controlled. Damaging populations are most commonly seen late in the growing season.