European corn borer
Ostrinia nubilalis (Hubner)
From: Solomon, J.D. 1995. Guide to insect borers of North
American broadleaf trees and shrubs. Argic. Handbk. 706. Washington, DC:
U.S. Department of Agriculture, Forest Service. 735 p.
Hosts. Sycamore, polar, yellow-poplar, peach, apple, pear.
This polyphagous species feeds on plants representing 131 genera of 40 families
including grains, grasses, weeds, herbaceous plants, flowers, and trees (Hodgson
1928). Corn is the preferred nonwoody plant. Trees are attacked only
occasionally unless growing near heavily infested preferred hosts (Anonymous
1979, Tedders and others 1981).
Range. Introduced into the United States during the early 1900's
and spread throughout the corn-growing areas east of the Rocky Mountains (Baerg
1951).
Description
Adult. Brownish moth with 24- to 29-mm wingspan (Vinal and
Caffrey 1919). Forewings yellowish and brown with some streaking, banding,
and spotting; hindwings grayish brown (Vinal and Caffrey 1919). Head
covered with light yellowish brown scales. Dorsum of thorax cinnamon brown
in males and light yellowish brown in females.
Egg. Circular to oval and slightly convex on upper surface,
averaging 0.97 mm long and 0.74 mm wide. Egg surface sculptured with
shallow pentagonal pits. When first deposited, eggs opaque to iridescent
white and within 2 days assume yellowish tinge (Vinal and Caffrey 1919).
Larva. Measures about 25 mm long with head capsule width of
about 2.2 mm when mature. Head and thoracic shields shiny brown and
mottled with black. Dirty white to pink body, gray or light brown with
narrow, dark brown median line on dorsum; broad, pale brown to pink subdorsal
line; and narrow, pale brown lateral line. Freshly abdominal prolegs bear
almost complete circle of crochets (Peterson 1962, Vinal and Caffrey 1919).
Pupa. Light to dark brown and about 14 to 17 mm long.
Tenth abdominal segment extended to form dark brown to black cremaster bearing
eight long, hooked spines.
Biology. This borer overwinters within tunnels in its host as
mature larvae, which pupate in May and emerge as adults during June in
Illinois. Females deposit 500 to 600 eggs on leaves of host plants; egg
incubation is about 1 week. In herbaceous hosts, young larvae feed on
tassels and leaf sheaths and later burrow in stems and fruits. Development
of first generation is completed in July; most moths emerge during August.
Larvae of the second generation feed on, or within, hosts until the advent of
severe winter weather. Larval feeding is resumed during spring. This
borer has one or two generations per year (Baerg 1951, Vinal and Caffrey 1919).
Injury and Damage. On tree seedlings, the first sign of
infestation is rapid wilting and dying of foliage, terminal leaders, and lateral
branch tips, which at first may appear to be caused by a leaf disease.
Closer inspection reveals large holes, up to 6.5 mm in diameter, in stems just
above the lateral leaf axils, or occasionally just below the leaf axils.
Noticeable quantities of large granular frass and excrement accumulate near
entrances. The larval tunnel, kept relatively free of frass, extends in
the pith from the entrance hole almost to the terminal bud and may extend
several centimeters below the entrance hole.* On peach seedlings, injury
can range from 2-mm-diameter holes in the bark to injuries that cause
10-mm-diameter limbs to break under their own weight. A conspicuous gummy
exudate mixed with frass accumulates at larval feeding sites (Tedders and others
1981). In northern Italy, it causes considerable injury in tree nurseries
by boring into succulent stems and lateral shoots of poplar seedlings,
particularly clones that have strongly developed medullary tissue like that in
eastern cottonwood (Anonymous 1979). About 90% of the limbs on 1- and
2-year-old trees in a Georgia peach orchard were damaged by larvae that had
migrated late in the season from browntop millet that had been interplanted
among the trees (Tedder and others 1981). In a similar case, 30% of the
terminal shoots of 1-year-old sycamore nursery stock, and some yellow-poplar
seedlings, were tunneled by larvae in an Indiana nursery.* In every
recorded instance of significant damage to tree seedlings, more preferred hosts
such as corn, cover crops, or weeds, either grew nearby or were interplanted
with the trees. In such cases, the trees were attacked in late summer by
larvae that had migrated from the herbaceous plants.
Control. Numerous parasites have been recorded (Arnaud 1978,
Krombein and others 1979). Several insect parasites have been introduced
from Europe to control the borer, and appreciable results have been obtained in
some areas. Populations are adversely affected by dry summers and cold
winters. Crows and other birds are effective larval predators (Baerg
1951). Despite many natural enemies of this borer, populations have to be
controlled by insecticides, cultural methods, and planting resistant plant
varieties. Cultural controls include plowing under infested herbaceous host
plants and shredding or storing hosts in silos to destroy hibernating
larvae. Several insecticides are registered for control and are effective
when properly timed and applied.
*Marshall, P.T. August 31, 1978. (personal
communication). Indiana Department of Natural Resources, Vallonia, IN.
Larva(e). James Solomon,
USDA Forest Service. |
Larva(e) and damage to seedlings. James Solomon,
USDA Forest Service. |
Adult(s). Ronald Smith,
Auburn University. |
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