PESTS OF SWEET CORN

Many pests of sweet corn go unnoticed because they are hidden within the soil, stalk, ear, or whorl. Few insects feed on exposed sites where they can be easily detected and controlled before damage occurs. As a result, much attention needs to be focused on early recognition of both pests and their injury.

KEY TO SWEET CORN PESTS

A. Caterpillars that feed exposed and/or bore into whorl, stalk, or ear

  1. Corn earworm - Early instars; cream colored or yellowish-green with few markings; later instars: green, reddish, or brown with pale longitudinal stripes and scattered black spots; moderately hairy; up to 44 mm long; three pairs of legs, five pairs of prolegs (Fig. 192); as leaves unfurl, ragged holes and soggy brown frass apparent; feeds on tip kernels of ear; round emergence holes in shuck

  2. European corn borer - Cream to light pink caterpillar with reddish-brown to black head; body up to 26 mm long with several rows of dark spots; has three pairs of legs near head and five pairs of prolegs (Fig. 193); bores in stalk; tangled frass and silk near entrance hole; tassel and stalk breakage, ear dropping, small ears, and/or pin holes in leaves sometimes present

  3. Fall armyworm - Green, brown, or black caterpillar with black stripe down each side and yellowish-gray stripe down back; body up to 40 mm long (Fig. 194A); head capsule with pale, but distinct inverted Y (Fig. 194B); rarely found in North Carolina before July but may be common later; feeds on leaves, may attack ears near shuck; mature larva may bore into stalk

  4. Stalk borer - Brown worms with a dark brown band with some paler stripes; older worms are whitish or light purple (Fig. 195); infested plants sucker excessively and do not tassel properly, stems sometimes lodge; plants past the "whorl" stage are resistant

B. Beetles that feed on foliage or silks
  1. Corn flea beetle - Black, oval insect 1.3 to 2.5 mm long, tinged bronze or bluish-green; yellow markings on legs; basal antennal segment orange (Fig. 196); infested foliage with tiny round holes and bleached out spots or stripes

  2. Dusky sap beetle - Dark gray or brown, oval to oblong beetle with club-like antennae; body 3 to 4 mm long (Fig. 197); feeds on ripening pollen; found on tassels or in leaf axils where pollen has collected

  3. Japanese beetle - Shiny metallic green, 13-mm-long beetle with coppery brown wing covers (Fig. 198); feeds on silks and, in severe infestations, reduces pollination and kernel formation

C. Corn leaf aphid - Soft-bodied, pear-shaped, winged or wingless insect up to 2 mm long; body pale bluish-green with powdery coating and dark area around base or cornicles (Fig. 199); feeds in colonies and causes leaf yellowing and deformation; cast aphid skins along with black moldy tassels, leaves and silks indicate high aphid population

D.Spider mites - Tiny pale or reddish spider-like arthropods feed on leaves, shucks and silks (Fig. 200); heavily infested plants turn yellow or appear burned; sometimes silks are completely obscured by webs and mites

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