European Corn Borer, Ostrinia nubilalis (Hübner)

Leininger, T.D; Solomon, J.D.; Wilson, A. Dan; Schiff, N.M. 1999. A Guide to Major Insects, Diseases, Air Pollution Injury, and Chemical Injury of Sycamore. Gen. Tech. Rep. SRS-28. Asheville, NC: USDA Forest Service, Southern Research Station. 44 p.

Importance.-This pest of corn and over 100 other plants sometimes infests sycamore trees in the Eastern United States. Typically, trees are attacked only when growing near heavily infested preferred hosts such as corn and certain cover crops. In sycamore nurseries, the European corn borer may tunnel through and kill up to 30 percent of the terminals.

Identifying the Insect (fig. 15a).-Larvae have brownish mottled heads and grayish bodies with pinkish-brown stripes and are about 25 mm long. Adult moths are brownish with yellowish-brown forewings that are somewhat streaked. Eggs are oval and yellowish white.

Figure 15a. - Larvae of O. nubilalis Photo by James Solomon, USDA Forest Service

Identifying the Injury (fig. 15b, c).-The first sign of infestation is rapid wilting and dying of seedling terminals and branch tips. Holes 4 to 6 mm in diameter are found in tender shoots. Splitting the infested shoot will reveal a tunnel, frass, and a gray larva.

Biology.-Overwintering larvae pupate in April and May, and moths emerge from May to June. Females deposit 500 to 600 eggs on herbaceous hosts that hatch in a week. Larvae complete feeding in July, and moths emerge in August. Second generation larvae feed until fall and overwinter in their tunnels. There may be one to two generations per year. Infestation of sycamore tree typically occurs when heavily infested herbaceous hosts mature or are harvested, causing the larvae to migrate to other succulent hosts.

Figure 15b. - Terminal being killed by larval tunneling. Photo by J

Figure 15c. - Young stems with entrance holes, frass, and tunnel. Photo by James Solomon, USDA Forest Service

Control.-Preferred crops like corn or millet should not be planted next to sycamore nurseries. Chemical controls may be required.