Feeding mostly below ground, occasionally some foliage feeding. Dull brown caterpillar with broad pale stripe on back. Somewhat smaller than other cutworms when full grown.
…………………………………………………………………………….Dingy cutworm
Feeding
mostly below ground. Caterpillar with
grayish white body without markings.
Head has two distinct vertical dark brown bars.
………………………………………………………………………………….Pale western cutworm
Failure
to sprout, or weakened and discolored seedling. Kernel or surrounding soil contains small (¼ inch) yellow or
white, tapered larvae, without apparent legs or head
……………………………………………………..…………………………..Seedcorn maggot
Feeding
on foliage. Gray to light brown
caterpillar with a two rows of yellow dots along back.
…………………………………………………………………………………. Variegated cutworm
Roots
chewed off. Roots or below ground
portion of stem may be tunneled. Yellow
to red larvae up to 1½ inches, with distinct head and legs and ornate terminal
abdominal segment.
……………………………………………………………………….………….Wireworms
Roots
chewed off, sometimes to the main stem.
Roots may also be discolored or tunneled. Small (up to ½ inch) yellow or white larvae with distinct brown
head. Lodged and/or goosenecked plants
may be present. Continuous corn
only.
…………………………………………………………………………………Western corn rootworm
Leaves with yellow spots along midrib. Dead areas of leaves or entire leaves in more severe cases. Damage progresses from lower leaves. More common in field edges and drier parts of field. Undersides of damaged leaves covered with webbing, microscopic green mites, and clear round eggs.
………………………………………………………………………….Banks grass mite
Ragged leaf feeding in whorl. Large green or brown caterpillars with skin covered with microscopic spines (visible with 10X hand lens).
………………………………………………………………………….Corn earworm
Leaves
covered with masses of blue green, soft bodied insects. Yellowish or reddish discoloration may be
present.
………………………………………………………………………………..Corn leaf aphid
Narrow,
elongate feeding lesions on upper leaf surfaces, along with sawdust-like
material. Perpendicular rows of round
holes ("shot-holing") may also be present. Flesh-colored caterpillars with faint spotting.
………………………………………………………………………………..European corn borer
Ragged feeding on leaves late in season. Dark, irregularly striped caterpillars.
………………………………………………………………………….Fall armyworm
Ragged feeding on leaves, usually in field margins. Entire leaves often eaten to midrib.
………………………………………………………………………….Grasshoppers
Ragged feeding on leaves late in season. Similar to fall armyworm but feeding more likely to progress from bottom of plant and edges of feeding holes ragged rather than smooth. More common in areas of field with grassy weed problems. Dark, irregularly striped caterpillars with light-colored mottling on head. …………………………………………………………………………..Armyworm
Similar to Banks grass mite, but damage not progressive from lower leaves and leaf tissue on opposite side of leaf from colonies less likely to be discolored. Damage rare before flowering. Positive identification of both mite species should be left to an expert.
………………………………………………………………………….Two spotted spider mite
Elongate
skeletonizing of upper leaf surfaces, usually just before pollen shed. Small, active brown or black beetles, often
with yellow stripes on back.
……………………………………………………………………………….Western corn rootworm
Stalk tunneled.
Tunnels may contain flesh colored caterpillars with faint spotting.
………………………………………………………………………………..European corn borer
Stalks tunneled by cream-colored caterpillars with distinct
brown or black spots. Plants may break
just above ground because of internal feeding.
Larvae lose spots in fall and winter.
Limited to southeastern Colorado.
………………………………………………………………………………Southwestern corn borer
Tassels covered with masses of blue-green, soft bodied insects. Yellowish or reddish discoloration may be present.
……………………………………………………………………….Corn leaf aphid
Tassel tunneled, may break due to damage. Flesh-colored caterpillars with faint spotting.
………………………………………………………………………...European corn borer
Small, active brown or black beetles, often with yellow stripes on back feeding on tassel during pollen shed.
………………………………………………………………………..Western corn rootworm
Damage to silks and ear tip. Single large green or brown caterpillar with skin covered with microscopic spines (visible with 10X hand lens).
……………………………………………………………………….Corn earworm
Shank, ear, ear tip tunneled. Parallel rows of kernels damaged. Tunnels may contain flesh-colored caterpillars with faint spotting.
……………………………………………………………………….European corn borer
Silks, ear tips and ears damaged. Entrance to ear may be through husks rather than just through silks. Dark, irregularly striped caterpillar.
……………………………………………………………………….Fall armyworm
Silks, husks and ear tip damaged. Usually accompanied by signification defoliation.
…………………………………………………………………....Grasshoppers
Silks chewed down to ear tip, with little damage to husks. Small, active brown or black beetles, often with yellow stripes on back.
……………………………………………………………………Western corn rootworm
Silks, ear tips and ears damaged. Entrance to ear may be through husks rather than just through silks. Light brown caterpillar with lighter stripes. Three dark brown vertical bars on "collar" just behind head.
……………………………………………………………………Western
bean cutworm
Categories: Field corn, Insects, Mites, Field key
Date: 08/14/01