Insect Management & Control

The Production Guide provides the following recommendations for insect control. 

Thrips

Thrips cause serious crop stunting and yield loss from both direct feeding and virus transmission (tomato spotted wilt). All commercial peanuts planted in S. C. should be treated at planting with a preventative in-furrow insecticide (Thimet or Phorate 20G, or Temik 15G. See the following table for Thimet / Phorate rates based on row spacing.

Soil Insects

Lesser cornstalk borers attack pods, pegs, lateral stems, and the plant crown at the soil line during extended drought stress. Fields with lighter soils are particularly vulnerable. In addition to direct injury, this insect is associated with increased white mold and aflatoxin levels due to wounding of the plant. Rapid canopy closure and reduced soil temperatures reduce LCB risk. Irrigation is the best defense against lesser cornstalk borer. Granular Lorsban (13 lb/ac) can be applied at pod set (about 50-55 DAP) to high risk fields (sandy soils under drought stress). At least 1/4" rain is needed within 10 days of application to benefit from Lorsban. Lorsban also reduces pod damage from wireworm, burrower bugs, and southern corn rootworm feeding. Unfortunately, Lorsban causes outbreaks of corn earworm, granulate cutworm and spider mites under drought stress later in the season.

Burrower bugs primarily attack reduced-tillage peanut fields under drought stress. These are underground stink bugs which feed directly on kernels by piercing pods with their needle-like mouthparts. In addition to direct yield and grade loss, burrower bugs are associated with increased aflatoxin levels. Irrigation is also the best defense against burrower bug injury.

Wireworms are immature or larval stages of click beetles, and they commonly feed on peanut pods. Although wireworms are capable of causing significant injury, thus far economic damage to peanut has been minimal under S. C. conditions. The only practical treatment for wireworms is preventative Lorsban application.

Southern corn rootworm is the immature stage of the eleven-spotted cucumber beetle. This worm tunnels into peanut pods under high soil moisture conditions, usually in more organic soils such as found in bottom areas of a field. Rootworm injury has been a relatively minor concern thus far under S. C. conditions. Preventative granular Lorsban is the only practical treatment for rootworms.

Foliage Caterpillars

Corn earworm is the most common foliage feeding insect on peanuts. Corn earworms usually appear in peanut fields during the last week of July or first week of August after the moths emerge from corn fields. Corn earworms initially feed in plant terminals, then blooms, older leaves, and pegs as the worms mature.

Fall armyworms are not usually an economic problem on peanut, but can occur in very high numbers during outbreak years. This insect usually shows up in peanut fields in mid-August, a couple weeks after corn earworms first appear.

Granulate cutworm can defoliate small plants in June and can also be a problem late in August where Lorsban was previously used because Lorsban kills fire ants and other predators. Granulate cutworms have distinctive “sergeant” markings along the back. Granulate cutworms initially feed on blooms, then leaves, pegs, and pods as the worms mature. During the day cutworms can be found curled up under shed leaves and other organic matter on the soil surface. The larger larvae climb up the plant to feed at night.

Velvetbean caterpillars can defoliate late maturing peanuts rapidly during late September or October in the southern coastal plain counties of S. C, especially in Jasper, Hampton, Allendale, and Colleton counties. Velvetbean caterpillars range from light green to almost black, but the key identification characteristic is that the medium to large worms will thrash violently when handled. They are easy to control.

Scouting for Foliage Caterpillars:
Use a 3' shake cloth to look for worms starting the last week of July, especially on fields treated with Lorsban. Work the dowel handle up under the lateral stems to the plant crown and bend the other side of the plants over the cloth; then beat down vigorously 15 times to knock the worms onto the cloth. Shake the plants, bend them back out of the way, and count the worms on the cloth. Also count the worms under the cloth on both sides of the row to calculate worms per row ft. Check at least three areas of the field.

Rank-growing, unstressed peanuts can tolerate 8 foliage feeding worms per row ft. The treatment threshold is 4 worms per row ft. on stressed plants which have not lapped the middle or where Lorsban has previously been applied. Georgia Green is more susceptible to foliage feeding because this variety has a smaller, slower growing canopy. Irrigation is the best defense against foliage feeding worms.

Spider mites

Spider mites can damage drought stressed peanuts in August and September. Stressed fields should be spot checked for yellow “hits” which indicate where mites are feeding. Spider mites can be seen with a hand lens on the underside of leaflets. Comite and Danitol are labeled for mite control, but these products require ground application, thorough coverage, and potentially a second application in 5 days. Lorsban application greatly increases the risk of mite outbreaks. Irrigation is the best defense against spider mite injury.

 For more information contact Jay Chapin, 803-284-3343, jchapin@clemson.edu.