PESTS OF SMALL GRAINS
Extracted from INSECT and related PESTS of FIELD CROPS (AG-271)
Placed on the Web 6/95 by the Center for Integrated Pest Management, NCSU
The production of small grains in North Carolina is concentrated in the Piedmont and Coastal Plain
counties. Approximately 212,550 hectares (525,000 acres) of rye, oats, wheat, and barley were planted for
grain in 1980, wheat being most prevalent. In addition, some small grains are utilized as cover crops. Acreage and production, however, are erratic and respond quickly to variations in weather, pest populations,
and economic conditions.
Key to Pests of Small Grains
A. Insects and mites that pierce tissues to extract sap.
B. Chewing insects that feed above ground
- Aphids - These winged or wingless, pear-shaped insects are usually less than 3 mm long
and feed in colonies. They are basically green, yellow, or pink and have a pair of appendages on the
abdomen known as cornicles. The extent of damage caused by these aphids varies, but nearly all
aphids cause some discoloration or mottling of the foliage.
- Corn leaf aphid - Up to 2 mm in
length, this pale
bluish-green insect has a dark area around
the base of its cornicles and a fine, powdery film over its body. This aphid causes a yellow mottling of the foliage.
- English grain aphid - Up to
2.5 mm long, this aphid is usually pale green (though sometimes
yellow or pink) with a dark blotch on its back. The insect feeds on the foliage but causes more
damage when it feeds on ripening kernels, causing them to shrivel.
Greenbug - Up to 2 mm long, the wingless
form of the greenbug has a pale yellow to bluish-green abdomen with darker
green, longitudinal streaks. The head, which is often a pale,
strawlike color, is lighter than the rest of the body. As it feeds on the foliage, this aphid causes
red spots which gradually enlarge. Eventually leaf tips turn brown. Circular areas of yellow
plants with dead plants in the center, known as "greenbug spots," may continue to enlarge.
- Chinch bug - This 4 mm-long, black
bug has opaque wings, each marked with a black triangle.
Feeding anywhere from the roots to the upper leaves, the smaller, wingless, red and black
nymphs cause dwarfing, lodging, and yield reduction. Young plants may wilt and die.
- Hessian fly maggot - This 2 mm-long, white to tan, legless larva feeds along with other
maggots behind the leaf sheath where the leaf joins the stem. Leaves become thickened and
weakened stems may break when the grain heads.
- Armyworms - Reaching a maximum length of 30 to 40 mm, these smooth-skinned caterpillars are
voracious foliage feeders. They have 5 pairs of prolegs.
- Armyworm - This pale green to brownish-green caterpillar is 30 to 35 mm long when fully
grown and has three dark longitudinal stripes. Its head capsule has
markings like those of the
fall armyworm but they are lighter or less intense
- Fall armyworm - This green, brown, or black larva (up to 40 mm long) has a dark head capsule
usually marked with a pale, but distinct, inverted "Y." A darker, curved marking occurs on
each side of the "Y" (Fig. B). A black, longitudinal strip runs down each
side of its body and
a yellowish-gray stripe runs down its back. The larva attacks small grains only in the seedling
stage during late summer or fall.
- Cereal leaf beetle adult -
About 6 mm long, this beetle has a blue-black body, brownish-yellow
legs, and a reddish-brown thorax (area behind the head) (Fig. A). The beetle
chews leaves, leaving longitudinal holes between the veins.
- Cereal leaf beetle larva -
About 6 mm long when fully grown, this soft-bodied, yellow larva is
usually coated with black, fecal material (Fig. B). It has three pairs
of legs near its head. The larva feeds between the leaf veins on surface leaf
tissue, leaving longitudinal gray or white patches instead of holes. Infested
fields may have an overall whitish cast.
- Grasshoppers - Many species of variously colored grasshoppers, ranging in length from
19 to 38 mm, feed on leaves and stems of small grains, eventually causing the
heads to fall to the ground.