B. Insects that feed on pods
- Potato leafhopper - Spindle-shaped and up to 3 mm long, potato leafhoppers
are green with yellowish to dark green spots (Fig. 46). They usually jump
instead of fly when disturbed. Potato leafhoppers extract sap from the undersides of leaves
causing them to crinkle and curl downward. Infested plants become yellow or bronzed and
- Thrips - Spindle-shaped and 1.2 mm or less in length, thrips are yellow,
amber, brown, or black. Adults have two pairs of wings which are fringed and have brown
crossbands (Fig. 47 A to C). Immature thrips are white or yellow with red eyes.
Thrips are pests during hot, dry weather. They cause whitish flecks or streaks on leaves and
blossoms, and they deposit black specks of excrement.
- Twospotted spider mite - Tiny (almost microscopic) pale to dark green,
twospotted spider mites have two or four darkly colored spots. Adults and nymphs have eight
legs (Fig. 48). Larvae have six legs. Females are oval and 0.3 to 0.5 mm long.
Males are somewhat diamond shaped. Infested foliage becomes silvery because of pale yellow
stipples. Leaves eventually become pale and die. Silken webs are spun on the underside of leaves
as the mites feed.
- Corn earworm - Early instars of corn earworms are cream colored or yellowish green
with few markings. Later instars are green, reddish or brown with pale longitudinal stripes and
scattered black spots (Fig. 49). Corn earworms are moderately hairy and grow
to 44 mm long. They have three pairs of legs and five pairs of prolegs. They attack beans in fall
and eat holes in pods.
- European corn borer - These caterpillars are grayish pink with a dark head and rows
of small brown doughnut-shaped spots on the back (Fig. 50). European corn
borers grow to about 26 mm long and bore into the pods.
- Cowpea curculio adult and larva (Fig. 51 A,B) - Adults are black
humpbacked weevils 6 to 7 mm long. Larvae are pale yellow and have brown heads. Larvae are
legless and grow 6 to 7 mm long. Curculios leave feeding scars - small holes in pods and peas;
larvae feed inside green seeds.
- Stink bugs - Adults are green or brown shield-shaped insects up to 19 mm long;
nymphs are pale green or green with orange and black markings (Fig. 52 A,B ). Stink
bugs pierce buds, pods, and seeds and cause buds to be malformed and plants weakened.
C. Insects which damage seeds and roots and bore in stems
- Bean leaf beetle larva - The whitish larva (up to 10 mm long) are dark at both ends
and have three pairs of prolegs near the head (Fig. 53). They are minor pests of
- Lesser cornstalk borer - These slender, bluish-green caterpillars are up to 19 mm
long and have brown rings around the body, three pairs of legs near the head, and five pairs of
prolegs on the abdomen (Fig. 54). Young larva bore into stems and sometimes
disrupt the growing point.
- Limabean vine borer - Gray when young, these caterpillars later become bluish-green
and sparsely covered with long yellowish hairs. Linnaean vine borer caterpillars grow up to 25
mm long and have three pairs of legs near the head and five pairs of prolegs on the abdomen (Fig. 55). They move from the leaves into stems, usually near nodes where they
cause galls up to 70 mm long and 20 mm around to develop. Short, loose, silky frass tubes are
connected to entrance holes.
- Seedcorn maggot - White to yellow-white maggots up to 7 mm long (Fig. 56) feed on seed contents causing poor germination and tall spindly seedlings.
Seedcorn maggots have no legs. The head is pointed.
Return to AG-295 Table of Contents