PESTS OF PEANUTS


North Carolina Cooperative Extension
Extracted from INSECT and related PESTS of FIELD CROPS (AG-271)
Dated 5/82
Placed on the Web 10/94 by the Center for Integrated Pest Management, NCSU

In 1980, peanuts were planted on 68,016 hectares (168,000 acres) of North Carolina farm land. Since all parts of the peanut plant are attacked by an array of pests, peanut farmers must be constantly on the lookout for insect and mite problems. It is impossible to predict what problems a grower will encounter in a given year due to variation in cultural practices, weather conditions and other factors. The following pests, however, are most likely to be encountered in North Carolina though perhaps not in every field every year.


Key to Peanut Pests

A. Chewing insects that consume above-ground plant parts

  1. Caterpillars - These soft-bodied, moth larvae have three pairs of legs near the head and four or five pairs of prolegs (Fig. 1A and B).

    1. Armyworms - These variously colored caterpillars have five pairs of prolegs (Fig. 1B), are occasionally foliage pests, and are difficult to chemically control.

      1. Beet armyworm - Dark-headed (Fig. 2B) and green or black, this larva sometimes has three longitudinal, light stripes and usually grows about 25 to 30 mm long. A small, black spot, located above the second leg behind the head (arrow), occurs on each side of the body (Fig. 2A). Heavily infested plants may be skeletonized. Young larvae often web leaves together.



      2. Fall armyworm - Green, brown, or black, this caterpillar reaches a maximum length of 30 to 40 mm and often has a distinct, inverted "Y" (Fig. 2C). The worms sometimes appear in large numbers in August and September.

    2. Corn earworm - When fully grown, this larva is green, reddish, or brown with pale longitudinal stripes and scattered, black spots. Early instars are fuzzy, cream colored or yellowish green with few markings. Larval instars vary from 1.5 to 44 mm in length and have five pairs of prolegs (Fig. 1B). Earworms feed on leaves, stems, and occasionally pegs.

    3. Cutworms - These chunky, sluggish caterpillars are active primarily at night; they feed on foliage and occasionally pods. They have five pairs of prolegs.

      1. Black cutworm - Varying from light gray to black in color and often appearing greasy, this caterpillar grows from 3.5 to 46 mm in length. The skin of this cutworm is granulated, the granules resembling rounded, flattened pebbles (Fig. 3A).

      2. Granulate cutworm - Growing from 2 to 38 mm long, this caterpillar has a pale brown head, a dark brown band down its back, and brown sides with faint stripes. The skin granules of this cutworm are like blunt cones as high as they are wide (Fig. 3B).

    4. Green cloverworm - This pale caterpillar, 15 to 30.5 mm in length, is distinguished from all other caterpillar pests of peanuts by the presence of only four pairs of prolegs (Fig. 1A).

    5. Velvetbean caterpillar - This pale green to black caterpillar has a light stripe along both sides of its body. It has five pairs of prolegs (Fig. 1B), varies from 2.5 to 48 mm long, and wiggles rapidly when disturbed. During September or early October, this caterpillar may attack both terminal buds and foliage.

  2. Spotted cucumber beetle - About 6 mm long, this yellowish-green beetle has black legs, antennae, and head as well as 12 black spots on its back (Fig. 4). The beetle feeds on unopened leaflets. As leaflets open, they are riddled with oblong or irregularly shaped holes.

B. Piercing-sucking pests which feed on above-ground plant parts (Fig. 5A to D).

  1. Cowpea aphid - This small, pear-shaped insect (Fig. 5) is no longer than 2 mm. The adult of this species is black with white appendages. The nymph is pale gray with a powdery coating. This insect feeds in colonies on the underside of leaves, causing the foliage to turn yellow and also excretes a sweet, sticky substance known as "honeydew." Black sooty mold often grows on the surface of this excretion.

  2. Potato leafhopper - This tiny, 3 mm long, yellowish- to pale-green insect (Fig. 5B) has yellow or dark green spots which can be observed under magnification. It feeds on the underside of leaves, causing a yellowing from the leaf tip back (hopperburn).

  3. Tobacco thrips - Slender, yellowish-brown, and about 1 mm long, this tiny insect (Fig. 5C) rasps leaves and causes them to pucker and lose color.

  4. Twospotted spider mite - Almost microscopic, this yellowish- to dark-green mite has two or four dark spots on its back (Fig. 5D). It has eight legs as an adult, but only six legs as a larva. It feeds on the underside of leaves, causing the foliage to turn silver-gray. Webs may be noticeable if the mites are numerous.

C. Insects that feed below ground.

  1. Beetle larvae - These larvae have three pairs of short legs near their head (Fig. 6).

    1. Southern corn rootworm - About 15 to 16 mm long when fully grown, this beetle larva (Fig. 6A) is yellowish- white with a wrinkled body. It has a hardened, brown shield over its last abdominal segment. Most injurious in heavy, poorly drained soils or following winter cover crops, this pest bores into young pods or attacks pegs before pods develop.

    2. Wireworms - Ranging from a few millimeters in length to 24 mm when fully grown, several species of these slender larvae (Fig. 6B) feed within the underground plant parts of the peanut. Infested plants become yellow and less productive.

  2. Lesser cornstalk borer - Slender, bluish-green, and brown-striped, this caterpillar has brown rings around its body. It is about 19 mm long when fully grown. It may feed externally or tunnel into underground plant parts. Developing nuts are often hollowed out.