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Plant NameTypeDescription 
Root, stalk, and ear rotsCornDiseaseSeveral fungi cause rots of roots, stalks, and ears of corn. These fungi may be carried on the seed, and may result in poor germination and seedling death. Roots show brown decayed spots. As the disease progresses, it moves from roots into the crown and is often associated with stalk and ear rots. The stalks are weakened and may break. Plants may die prematurely. The inside of affected stalks is typically discolored and rotted. Ear rot is typically seen as white, gray, pinkish, or dark fungal growth over the kernels. The fungi may overwinter in the soil or on plant debris.
Seed rot and seedling blight (damping-off)CornDiseaseSeveral fungi can cause seed rots and seedling blights of corn. These can be carried on the seed, or can overwinter in the soil or infected plant debris. Seeds planted in cold soils may rot without germinating or the seedlings may die prior to emerging from the soil. Seeds planted in warmer soils typically germinate, but the emerging seedlings may be stunted and have brown, rotted roots and crowns. Seed rots and seedling blights are more of a problem in cold soils with poor drainage, and in conjunction with overwatering. Seedling blight and damping-off are typically considered the same disease. However, the name 'damping-off' is often used when infection is severe enough to kill the seedlings.
SmutCornDiseaseTwo types of smut occur on corn in the Pacific Northwest. Both are fungal diseases. Common smut may occur on any above-ground portion of the plant, causing gall-like swellings. The galls are initially covered with a greenish to silvery layer of tissue which later dries and breaks open, releasing a mass of olive-green to black spores. Leaf galls typically are hard and do not break open. Common smut is more serious during hot weather. Head smut typically attacks only the tassels and ears. The infected ears and tassels may form leafy structures instead of reproductive parts, or may become masses of spores. The spore masses have thread-like strands of corn vascular tissue in them, which helps distinguish head smut from common smut. Both diseases may be spread by wind-blown spores, and head smut spores may also survive in the soil or on the seed surface.
Brown marmorated stink bugCornInsectThe brown marmorated stink bug (BMSB) is an introduced pest species from Asia that is spreading quickly across the United States. Nymphs and adults feed on a wide variety of plant hosts. BMSB prefers to feed on fruit, seeds, and seed pods, but will also feed on stems and leaves of some hosts. Both adults and nymphs have piercing-sucking mouthparts and inject digestive enzymes into plant tissues to aid in feeding. On corn, BMSB feeds on the outside of developing ears and injures the kernels inside the husks. Kernels damaged early in development fail to fill completely and may appear shrunken or stunted. More mature kernels collapse and turn brown, especially after cooking. Secondary damage from rot may also occur. BMSB may also feed on stems, as well as on silks or tassels where they may affect pollination. Other known vegetable hosts of BMSB include tomatoes, peppers, beans, and cucumbers. One or two generations of BMSB per year are expected in the Pacific Northwest. Adults overwinter in sheltered locations (including houses, where they can become a significant nuisance pest). In the spring, light green to white eggs are laid in groups of about 20 to 30 on the underside of leaves. Young stink bugs, or nymphs, are black with a red-and-black striped abdomen. Nymphs often feed in groups when young. Older nymphs are dark with white bands on body, legs, and antennae. They may feed in groups or singly. Adults are a little over 1/2 inch long, with a shield-shaped body. Body color on adults is mottled gray and brown, while the legs and antennae have alternating dark and light bands. The abdomen also has dark and light bands which are visible at the edge of the wings. NOTE: BMSB adults closely resemble other stink bugs found in WA and OR. For more information on BMSB identification, see FS079E, Pest Watch: Brown Marmorated Stink Bug, available at
Corn aphidsCornInsectAphids are small, soft-bodied, pear-shaped insects. They may vary in color from yellow to green to dark. Aphids typically feed in colonies on the leaves, often preferring the newer growth. Infested leaves turn yellow and may wilt or show other signs of water stress. Feeding aphids often produce large amounts of honeydew, a sweet, sticky material which may attract ants or become covered with a dark growth of sooty mold.
Corn earwormCornInsectThe corn earworm is the caterpillar of a light to dark brown moth with a 1-1/2" wingspan. The caterpillars are up to 1-1/2" long at maturity. They vary widely in color, but typically have darker stripes along a cream-colored to greenish body. The first generation may feed on the center shoots of the corn, attacking the tender new leaves. Later generations may feed on the silks, preventing pollination. They may also feed in the ear itself, damaging kernels and leaving behind dirty-looking droppings. The droppings may be visible at the tip of the ear. Several generations may occur in one season, as the corn earworm can progress from egg to adult moth in as little as one month during favorable conditions. Corn earworm pupae overwinter in the soil. Peppers, tomatoes, beans, and many other plants are also attacked.
Cutworms and armywormsCornInsectCutworms and armyworms are the larvae of noctuid moths. These common moths are medium-sized with fairly dull coloration. The greenish, grayish, or tan caterpillars are hairless, nocturnal, and generally spotted, striped, or otherwise marked. They may be 1/4" to 1" in length and tend to curl up when disturbed. Cutworms may feed by cutting through stems of young plants an inch or less above ground level. Several plants may be damaged in one night. While armyworms typically feed during the day, cutworms spend the day just beneath the soil surface or under debris near the host. They usually feed at night, so it is advisable to search for them with a flashlight in the dark. Weeds are their primary food source.
EarwigsCornInsectEarwigs are reddish-brown insects about 3/4" or less in length. Both males and females have pincers at the rear end. Earwigs are largely beneficial, feeding on many pests such as aphids, mites, and nematodes, as well as on algae, fungi, and decaying plant material. However, earwigs can also damage plants. They may feed on the corn silks, which prevents pollination and results in partially filled ears. Symptoms include short silks, partly filled ears, and earwigs present on the silks and in the ears.
Spider mitesCornInsectSpider mites are tiny, eight-legged mites which may range in color from yellowish to green or red. They typically feed on the underside of leaves, causing a yellowish to bronze stippling or speckling of the leaf. Severe infestations can cause entire leaves to turn yellow. Spider mite feeding is usually accompanied by webbing on both sides of corn leaves. The mites may be visible as "moving dust" in the webbing. Mite infestations are worse in hot, dry, dusty conditions.
Western spotted cucumber beetleCornInsectThe western spotted cucumber beetle is a pest of many ornamentals and vegetables. About 1/4" long, the adult beetles have yellow wing covers with black spots. The rest of the body is black. Adults feed on leaves of plants, while the larvae feed on the roots of some plants.