Burdock borer
Papaipema cataphtacta (Grote)
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. Cottonwood, boxelder, elder. Over 30 hosts--mostly
large-rooted thick-stemmed herbaceous plants--have been reported (Tietz
1972). Burdock and thistle are favored wild hosts (Bird 1898).
Broadleaf trees are occasionally attacked.
Range. Occurs from the northeast Atlantic Coastal region west
through New York and Pennsylvania to Minnesota and Colorado (Forbes 1954) and
south to Mississippi.
Description
Adult. Moderately robust yellowish brown moth with wingspan of
30 to 35 mm. Forewings generally straw yellow, scaled, with grayish brown
markings (Forbes 1954). Yellow spot on apex of each forewing.
Larva. About 29 to 35 mm long. Head pale yellowish brown
with darker brown at posterior or margin. Cervical shield light brown with
darker brown longitudinal stripes along each side. Pale white body with
four broad purplish brown stripes along entire length of body. These
continuous body stripes distinguished P. cataphracta from P. nebris,
which has stripes interrupted on first three abdominal segments by purplish
brown band (Decker 1931).
Pupa. Chestnut brown, generally smooth except for dorsal
punctations, about 14 mm long, cremaster with two small downward-pointing
spines.
Biology. Moths emerge from early September to early October
(Decker 1931, Drake and Decker 1927, Knutson 1944). Females deposit up to
2,000 eggs in the creases of rolled or folded leaf blades of dead grasses and
weeds; there, eggs overwinter and hatch the following spring. Initially,
newly hatched larvae burrow into stems of weeds. When the larvae are 2 to
6 weeks old, they leave their initial herbaceous hosts and move to new hosts,
which can be thick-stemmed woody plants. Most reports indicate May as the
time that larvae infest tree shoots, but infestations have been observed through
July and early August (Solomon 1988b). Field and cage studies show that
typical larvae wander considerably during development and repeatedly burrow into
susceptible shoots for 1 to 2 weeks, abandon them, and seek larger shoots.
In cages over clumps of cottonwood sprouts, single larvae have tunneled up to 12
separate shoots. In late July to early September, full-grown larvae in
cottonwood shoots usually abandon galleries and move to the ground, where they
form pupation sites of loose silk and frass just below the soil surface or under
debris. A few larvae remain in their hosts and simply enlarge tunnels in
the shoots to form pupation chambers. The pupal stage lasts 25 to 33
days. This borer has one generation per year.
Injury and Damage. Injury in cottonwood nurseries in Mississippi
usually becomes noticeable form late April to early May, when coppice sprouts
are 30 to 60 cm tall (Solomon 1988b). Injured stems are easily detected by
wilting and drooping shoots with browning or blackening leaves.
Examination of damaged shoots often reveals round entrance holes 2 to 3 mm in
diameter and 8 to 30 cm below the shoot tops. Entrance holes usually are
kept open but occasionally loosely plugged with frass. Frass is sometimes
fragmented and mixed with oozing sap on the stem just below entrance
holes. More typically, frass consists mostly of distincly white,
cylindrical excrement pellets 1 to 2 mm in diameter and 2 to 3 mm long near
entrance holes and on the ground below. Dissection of damaged cottonwood
shoots reveals galleries in the centers extending in either direction form the
entrance holes but usually upward or distally. Active galleries are kept
open and mostly free of frass, and are 2 to 4 cm long. Occasionally branch
tips and the aboveground part of seedling trees stems are killed (Washburn
1910). Young cottonwood trees have been moderately infested and damaged in
some areas. In surveys, 4 to 12% of the coppice shoots in cottonwood
nurseries in Mississippi have been attacked. About three-fourths of the
infested shoots die back or break (Solomon 1988b).
Control. Larvae are extensively parasitized by Chasmias
scelestus (Cresson) (Carlson 1979), Exorista sp., Gyrmnocheta
ruficornis (Williston), Lixophaga variabilis (Coquillett), Lydella
radicis (Townsend), and Winthemia rufopicta (Bigot) (Arnaud 1978,
Washburn 1910). Tree nurseries and young plantations can be protected from
infestation by plowing under cover-crop refuse and weeds adjoining new plantings
during autumn or early spring. Fence rows of weeds and grasses near tree
plantings can also be burned during winter to destroy borer eggs (Drake and
Decker 1927). Insecticides timed to correspond to earliest attacks can help
minimize losses.
Larva(e) in young cottonwood stem. James Solomon,
USDA Forest Service. |
Adult(s) female. James Solomon,
USDA Forest Service. |
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