Concentrated in the Coastal Plain and southern Piedmont counties, soybeans were planted in 1980 on 803,644 hectares (1,985,000 acres) of North Carolina farm land. Due to the length of the growing season and the nature of the crop, soybeans have as many insect pests associated with them as any other major crop produced in this country. Insect damage, however, tends to be more of a problem in the southern states due to the longer growing season. Regardless of geographic location, insect infestations in soybeans rarely become economically important until after full bloom.

Key to Soybean Insect Pests

1. Beetles - These chewing insects have hard, shell-like forewings (wing covers or elytra) which meet in a straight line down the middle of the back when the beetles are not in flight (Fig. A to E).
   
   1. Bean leaf beetle - This oval, red to brown and black beetle (Fig. A), 5 to 6 mm in length, feeds on the youngest tissue available. It usually, but not always, has three black spots on each wing cover. However, this beetle always has a black head as well as a black, triangular area on the forward margin of its wings.

   2. Blister beetles - These 12- to 19-mm-long, elongate beetles (Fig. B) may be black, gray with black spots, or black and yellow striped. Most species feed heavily on foliage along field margins while some prefer the flowers.

   3. Grape colaspis - This oval, yellowish-brown beetle is 4 to 5 mm long (Fig. C). Its wing covers appear slightly striped. The grape colaspis feeds on foliage, but rarely causes any significant damage.

   4. Japanese beetle - This oval, metallic green and copper colored beetle (Fig. D) is about 13 mm long. Many of these beetles typically congregate together and feed on soybean foliage in June or July.

   5. Mexican bean beetle - This yellow to copper colored beetle (Fig. E) is 6.0 to 8.5 mm long and has eight black spots on each wing cover. It feeds on the undersurface of leaves between the veins, leaving a lacy network which eventually turns brown.

2. Caterpillars - These soft-bodied, moth larvae have three pairs of legs near the head and three, four, or five pairs of prolegs (Fig. A to C).
   
   1. Armyworms - These smooth-bodied, variously colored caterpillars have five pairs of prolegs (Fig. C above), and are occasionally problem foliage pests.
      
      1. Beet armyworm - This dark-headed (Fig. B), green to black larva sometimes has three longitudinal, light stripes and usually attains a length of about 25 to 30 mm. A small, black spot occurs on each side of the second segment behind the head (Fig. A). Leaves often are skeletonized by large larvae and webbed together by young larvae.

      2. Yellowstriped armyworm. - Reaching a length of up to 45 mm, this pale gray to jet black caterpillar has a yellowish-orange stripe along each side and a pair of black triangular spots (Fig. D) on the back of most segments. This armyworm has a "Y" marking on its head capsule similar to that of the fall armyworm (Fig. C). It is primarily injurious to seedling stands.

   2. Corn earworm - When fully grown, this larva is green, reddish, or brown with pale, longitudinal stripes and scattered black spots. Occurring on soybeans during late summer, early instars are 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. C above). The corn earworm defoliates and damages blooms and pods.

   3. Green cloverworm - This pale green caterpillar, 1.5 to 30.5 mm in length, is distinguished from all other caterpillar pests of soybeans by the presence of four pairs of prolegs (Fig. B above).

   4. Soybean looper - After bloom, this light green caterpillar may cause severe defoliation. The looper has three pairs of prolegs (Fig. A above), reaches a length of 35 mm, tapers from the rear forward, and walks with a "looping" motion.

   5. Velvetbean caterpillar - This pale green to black caterpillar has a light stripe along both sides and five pairs of prolegs (Fig. C above), the last pair resembling a forked tail. It wiggles rapidly when disturbed. Length varies from 2.5 to 48 mm.

   
3. Mexican bean beetle larva - About 8.5 mm long when fully grown, the bright yellow spiny, soft-bodied larva feeds on the undersurface of leaves between veins. This feeding results in a lacy network which eventually turns brown.

1. Corn earworm - See section A.2.b. for description. Unlike the fall armyworm, the corn earworm's head capsule is light brown to chestnut colored and does not have a distinct, inverted "Y." The corn earworm chews into pod tissue and removes the seeds.

2. Stink bugs - These shield-shaped bugs (Fig. A,B) pierce the pods with their mouthparts leaving sunken, discolored spots on the seed.
   
   1. Brown stink bug - This dull grayish-yellow bug is 12 to 15 mm long (Fig. A). This bug should not be confused with another closely related, brown species, the beneficial, spined soldier bug (Fig. B). This mistake can be avoided by strict attention to the shape of the bug.

   2. Green and Southern green stink bugs - Ranging from 14 to 19 mm long, these two green species are difficult to distinguish from each other in the field.

1. Grape colaspis larva - This stout, grub-like larva has a dark brown head and grayish-white or tan body up to 7 mm long (Fig. 168A). It has three pairs of legs near its head and fleshy appendages on its abdomen. Areas of yellow, stunted plants sometimes indicate root damage by this pest.

2. Soybean stem borer - This white, legless larva (Fig. B) ranges in length from 1.5 to 15 mm. It bores in the pith of the soybean stem, girdling it from the inside and sometimes causing the plant to lodge at harvesting.

3. Threecornered alfalfa hopper - This green wedge-shaped bug (Fig. C) is 6.0 to 6.5 mm in length when mature. It girdles the stem by puncturing it with its "beak" to suck sap and by ovipositing within plant tissues. Stems may lodge or break easily before mature.