Stalk borer
Papaipema nebris (Guenee)
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, maple, elm, ash, poplar, catalpa, willow,
boxelder, sumac, elder, apple, peach, plum, hawthorn. A polyphagous
species that attacks both herbaceous and woody plants; recorded from 176 plant
species representing 44 families (Decker 1931, Filer and others 1977).
Corn is a preferred cultivated host; other Gramineae and giant ragweed are
favored wild hosts. This borer less commonly attacks hardwood trees.
Range. A native insect, occurs throughout the United States east
of the Rocky Mountains (Metcalf and other 1962) and from Nova Scotia west to
Manitoba (Decker
1931).
Description
Adult. Moderately robust brownish moth with wingspan of 25 to 40
mm (Decker 1931). Fore-wings varying shades of olive red or purplish brown
sprinkled with gray; some have a group of white spots in medial area.
Small white spots along distal third
of anterior wing margin and white to yellowish line curves toward hind
margin. Body reddish brown with white-tipped scales, producing overall
mouse gray color.
Egg. Globular, 0.6 by 0.4 mm, and pearly white when first
deposited, gradually turning to brownish gray or amber.
Larva. Head light brown with dark brown streak extending from
the ocelli to ventral margin of cervical shield (Peterson 1962). Dirty
white body with four broad purplish brown stripes (dorsal and subdorsal)
interrupted by distinct band of purplish brown around third thoratic and first
three abdominal segments; from 26 to 32 mm long when mature. Prothoracic
shield broad, partly divided, and yellowish to light brown with dark laterial
stripe. Anal shield yellowish to pale brown.
Pupa. Heavy bodied, brown, and 16 to 22 mm long.
Biology. Moth's emerge from mid-August to mid-October (Solomon
1988b). Up to 2,000 eggs are deposited by each female, usually in creases
of folded or rolled leaves of dead, dry grasses and weeds (Metcalf and others
1962). Eggs overwinter and hatch the following May or June. Newly
hatched larvae burrow in the stems of grasses and small-stemmed weeds and
continually seek larger succulent stems as they grow (Decker 1931). It is
usually during the late stage of development that larvae migrate from herbaceous
plants and attack young trees. Larvae wander considerably during
development, and each may feed on several shoots of the same plant, several
plants, or on many different species of plants (McDaniel 1935). Small
larvae usually enter herbaceous plants near their base and burrow upward;
however, as larvae grow, they may bore into stems at any point, usually
burrowing toward tips (Decker 1931). Larvae keep their galleries fairly
free of frass, expelling it from the entrance holes. Larvae have been
reported to molt from 7 to 14 times and require from 60 to 130 days to develop
(Decker 1931). Full-grown larvae usually abandon their hosts and move to
the ground, where they from oval cells below the soil surface in which to
pupate. Occasionally, larvae will remain in their hosts, forming pupal
chambers of frass and silk at the bottoms of their tunnels (Decker 1931).
Pupation occurs from late July to late August and averages 25 days (Deceker1931).
This species has one generation per year.
Injury and Damage. Sudden wilting, drooping, and dying of
succulent current year's growth, particularly terminals, on young trees during
late spring and summer is the first evidence (Filer and others 1977, Solomon
1988b). Closer inspection reveals larval entrance holes about 3 mm in
diameter near the base of injured terminals or branches. Frass with
distinct excrement pellets mixed with sap are ejected from entrance holes and
are often present on the bark or foliage beneath (McDaniel 1935). Larvae
tunnel in the stem center and often consume most of the woody contents of
shoots; such weakened branch tips break off readily. Many branch tips on
young trees can be damaged in a short time. Larvae prefer thick-stemmed
herbaceous plants. This borer occasionally infests succulent current-year
shoots of young deciduous trees and woody shrubs. Economically significant
damage to trees rarely occurs over wide areas, but noticeably losses sometimes
occur in nurseries and young plantations and, to a lesser extent, to young trees in natural stands (Solomon 1988b).
Control. The most important control in forest tree nurseries and
young hardwood plantations is to destroy breeding sites by thoroughly cleaning up
host weeds in fall and winter. Mowing fence rows and field borders is
effective but must be done about mid-August just before oviposition.
Mowing too early will drive larvae into suscepible crops (Metcalf and others
1962). Damage can sometimes be reduced on young trees if the wilted tips
are promptly pruned below the injury and destroyed. Populations are
adversely affected by many hymenopterous and dipterous parasites (Arnaud 1978,
Krombein and others 1979); predaceous birds, mammals, and insects; and diseases
(Decker 1931). Chemical controls may be needed occasionally.
Larva(e) gallery in shoot. James Solomon,
USDA Forest Service. |
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