Ask the Experts

 
Q. At what point in the growing season is scouting for insect pests no longer beneficial?

A. “From the time they come out of the ground until they are dug, peanuts should be checked weekly for insects and/or damage,” says James Weeks, Auburn University Extension entomologist.

“However, there are times during the growing season when scouting should focus on certain insects.”

Early season scouting, explains Weeks, should focus primarily on thrips damage and possibly soil insects like white grubs that affect the plant stand.

Thrips are the vector for Tomato Spotted Wilt Disease, and a plant stand with skips or bare spots is more likely to have TSWV around those areas.

“Mid-season, growers should focus on foliage feeders like cutworms and corn earworms,” Weeks, who is based at the Wiregrass Research and Extension Center in Headland, Ala., says. “Also, during this part of the season is when you should concentrate on damage from leafhoppers and three-cornered alfalfa hoppers.”

If three-cornered alfalfa hoppers are present, the first sign may be the feeding sight of the insects. They feed around the stem of the plant and cause a scar, referred to as a “girdle.” The damaged sight may turn purple, and later in the season, the terminal of the plant will turn yellow because of the disruption of photosynthates above the girdle.

Weeks says in mid-to late-season, during pegging, scouting should focus on soil insects and damage to pegs and pods.

Lesser cornstalk borers (LCB) are a semi-subterranean insect, that will bore into and feed on stems, pegs or pods. Sand tubes, (bottom, right) can be found attached to the peanut plant where LCBs are feeding. They are generally found in hot, dry weather conditions. Nonirrigated, sandy fields are at greatest risk for damage fromLCBs.

Late season – within a week or two of digging – scouting should focus on velvetbean caterpillar or other pests that could defoliate peanuts, Weeks says.

“Although high populations of insects can cause economic losses to peanuts at any time of the year, if levels are monitored and treatment thresholds are followed, peanuts will not suffer significant economic losses,” Weeks says. PG

Scouting Tips:
• Scout once a week.
• Take enough samples – at lease 10 per field – to cover all field borders and interior areas that might have different soil types or growth habits.
• Sample to include 2 to 3 linear foot of row, and brush down or shake plants to dislodge foliage-feeding worms.
• Pull back vines to identify and count any caterpillars that are present.
• Look on the underside of lateral limbs for webs or holes where LCBs might be feeding.
• Check pegs and developing pods in the sample area.
• Inspect foliage and/or stems for leafhoppers, spider mites or three-cornered alfalfa hopper damage.