EUROPEAN CORN BORER (ECB): Ostrinia nubilalis (Hübner) Order – Lepidoptera: Family – Pyralidae

DISTRIBUTION: This eastern European species has spread from Manitoba to FL and is found in all but the six most western states in the United States.

DESCRIPTION:Eggs (Fig 2) are about the size of pinheads and may overlap each other in a “fish scale” manner. The circular almost flat eggs turn from white to yellow as they mature. Newly hatched larvae (Fig 3) have black heads and pale yellow bodies with several rows of brown to black spots. Full-grown larvae (Fig 4) are pinkish and spotted on the upper surface, cream colored on bottom. The pupae (Fig 5) are brown to reddish-brown, 5-6 times as long as wide and ½-5/8” in length.

Adult ♀s (Fig 1 to right) have robust bodies ranging from pale yellow to light brown. The body may be 1” long and the wingspan 1.5” long (0.6” in resting stage). Two zigzag lines of a darker color usually cross the forwing. The ♂s (Fig 1 to left) are normally darker in color and have more slender bodies.

HOSTS: Over 200 host plant species. The primary host crops are corn, sorghum, soybean, millet, oat, barley, potato, and beans.

DAMAGE: In corn, ECB damage results in poor ear development, broken stalks, and dropped ears. Most yield reduction is due to early stage larval feeding in leaf and conductive tissues. Autumn winds and dry weather, coupled with tunneling in stalks and shanks, results in loss of ears during harvest. Stalk rot (fungus) is encouraged by ECB damage. In crops other than corn, the pattern of damage is variable with both stalk and fruit damaged in some cases.

INSPECTION TIPS: When corn is 16-22” in extended leaf height, examine the whorl leaves for fresh “shot-hole” feeding (small random holes). Pull out the damaged whorl, unroll the leaves and examine them for live larvae. Later, excrement that looks like wet saw dust will indicate where a larvae is feeding within a stalk (cut and examine). Larvae may be observed around egg masses (middle 1/3 of plant, underside leaf, midrib), in leaf axils, behind leaf sheaths, on tassels, or on the ear. This feeding generally occurs in the “ear zone” (two leaves above and below the primary ear).

LIFE CYCLE: ECB has 1-4 generations a year depending upon weather (Fig 6). ECB overwinters in the larval stage, with pupation and emergence of adults in early spring. Adults live 18-24 days. The preoviposition period averages 3.5 days. The ♀ often deposits 400-600 eggs during her lifetime. Eggs hatch in 4-9 days. Larvae normally have 6 instars with a total development time of about 50 days. Young larvae feed within the whorl especially on the tassel. Older ECB burrow into stalk and ear. The final instar overwinters in stalk or stem. The duration of the pupal stage is usually about 12 days and usually occurs in April/May and then later if more than one generation occurs.

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