EUROPEAN CORN BORER: Ostrinia nubilalis, Pyralidae

ADULT: Moths have slender bodies and a wingspan of 1 in. Body and wing color are yellow to light brown with many zigzagging lines across wings. Legs are white. Males are darker than females.

EGG: The white, oval, flat eggs are deposited usually under leaves in clusters averaging 14 to 20 (range 1 to 162) in an overlapping fashion resembling fish scales. Eggs turn yellow and then black heads of larvae are visible just before they emerge. Larvae emerge in 3 to 5 d.

LARVA: Newly emerged larvae have a black head and a yellow body with several rows of dark spots. Full grown larvae are 1 in. long, pink to light brown to gray, with faint spots on their backs. They are cream-colored on their underside.  Larvae have three pairs of true legs and five pairs of prolegs.  Larval development takes 25 to 30 d.

PUPA: The insect pupates within the corn plant.  Pupae are 1/2 to 3/4 in. long, and light to dark reddish-brown. Adults emerge in 10 to 15 d.

GENERATION TIME: 38 to 50 d.

DAMAGE: Although considered to be the most destructive corn pest in North America, fall armyworm and corn earworm are the most important in Florida.  O. nubilalis is confined to mostly the northern and western corn growing areas of the state. Larvae of the first generation begin feeding on leaves in the whorl, but later bore down the leaf midribs into the stalk. This results in reduced yield by limiting nutrient transport to developing ears. Stalk boring by the second generation in the crop weakens stalks and ear shanks causing stalk breakage and ear drop. These tunnels provide access to infection by pathogens that may be more responsible for weakened and broken stalks and shanks than the tunnels themselves.

CONTROL: Frass and silk near stalk entrance holes are evidence of stalk boring.  Host plant resistance is emerging as an effective control stragegy for this pest in both sweet and field corns.  Moths can be monitored with light and pheromone traps.  Chemical control of this insect is difficult, because it is only susceptible during the 2 to 3 d period before the larvae begin to bore into the corn leaves and stalks.  Therefore, flights of moths should be monitored and fields sampled for eggs.  Foliar sprays should be timed to kill larvae after they emerge from eggs and before they begin to bore into the tissue. Pesticides are available for at-plant and post-emergence banded and broadcast applications. Formulations, rates, and pre-harvest intervals of insecticides for European corn borer control are listed below for sweet corn (Table 1) and field corn (Table 2).