Cottonwood clearwing borer
Paranthrene dollii (Neumoegen)
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. Poplar, willow. Eastern cottonwood is the major
host, but balsam poplar and the hybrid poplars are also attacked. Many
other poplars probably susceptible. Observed occasionally in black willow;
probably occurs in other willow species.
Range. Throughout the eastern half of the United States westward
to the edge of the Great Plains (Engelhardt 1946); most destructive in the South
(Solomon 1988a).
Description
Adult. Reddish clearwing moth with opaque, dark brown forewings
with violet or coppery reflections. Hindwings semitransparent and reddish
brown. Wingspans from 30 to 40 mm. Male antennae robust, bipectinate,
and strongly dilated at tips; female antennae simple. Head black and shiny
with rust red fringe just behind top. Thorax black with lateral buff and
reddish tufts. Abdominal segments 1, 2, and 3 black; 4, 5, 6, and 7 reddish; and
segments 2 and 4 narrowly ringed with reddish yellow. Legs pale red with
black femora (Engelhardt 1946).
Egg. Oval and dark brown (Morris and others 1975), measuring 0.7
to 0.9 mm wide and 1.0 to 1.2 mm long (Eroles-Harkins 1983).
Larva. White to light pink with brown head and thoracic shield;
25 to 32 mm long and 4 to 5 mm wide at maturity (MacKay 1968, Morris and others
1975). Thoracic and abdominal spiracles elliptical, former being larger
than latter. Ventral prolegs on abdominal segments 3 to 6 bear parallel
rows of well-developed uniordinal crochets; anal prolegs posses only one row of
crochets (Peterson 1962).
Pupa. Brown, smooth, shiny, and 20 to 25 mm long. Upper
surface of each abdominal segment with two parallel transverse rows of spines.
Biology. Adult life span is 10 to 18 days (Eroles-Harkins
1983). Adult males were caught in pheromone-baited sticky traps in north
central Florida from early April to late June and from mid-September to
mid-November (Sharp and others 1978). Similar trapping by Eroles-Harkins
(1983) in west central Mississippi showed three peaks: mid-April to
mid-May, late June to mid-July, and mid-August to early September. Moths
are diurnal; males confine their flight mostly to 12 noon to 4 p.m. (Solomon and
others 1982). Females oviposit for 2 to 6 days in deep cracks, crevices,
and other cavities, usually in the basal meter of the tree. Larvae have 12
instars in the field and 15 to 17 instars in the laboratory (Eroles-Harkins
1983). Upon hatching, larvae feed initially in bark and later enter the
wood. Galleries in wood at the tree base meander, whereas those made
higher on the trunk tend to follow the pith. Several larvae often
infest a stump, but galleries generally do not intersect. Galleries are
about 10 cm long for mature larvae. Mature larvae, before constructing
silk-lined pupal chambers near the distal end of the galleries, make short
tunnels almost to the bark surface, keeping exit holes closed with flimsy bark
flaps. When the pupal stage nears completion, the pupae work their way up
the galleries with the aid of abdominal spines and protrude through exit holes
for emergence. In its northern range, this species requires 2 years for
its life cycle (Engelhardt 1946), whereas, in Mississippi, one or two
generations may be completed in 1 year (Cook and Solomon 1976). Biological
observations are confounded by the occurrence of various-sized larvae in trees
throughout the growing season and the occurrence of at least three peak male
moth catches in pheromone-baited traps.
Injury and Damage. Early signs of attack are sap flow and frass
pushed from the entrance holes; attacks may occur at almost any point on the
stem but are most common at the base (Morris and others 1975). Stems may
have multiple tunnels from repeated attacks. As larvae grow, clumps of
granular frass accumulate at the base. Galleries are partially filled with
small, round, reddish pellets of excrement and woody fragments (Engelhardt
1946). Stems less than 4 cm in diameter frequently develop galled or
cankerlike swellings. Large stems exhibit only slight (or no) swellings
(Cook and Solomon 1976). A survey revealed that 12% of 1- and 2-year old
trees in cottonwood plantations in Mississippi River bottoms of Arkansas and
Mississippi were infested (Abrahamson and Newsome 1972). In nurseries,
populations in 1-year-old plants are seldom heavy; sizeable infestations build
up in 2-year-old and older rootstocks. After several harvests, every
rootstock may be attacked, requiring clearing and destruction of stumps.
Infested trees are weakened and sometimes break off or may be killed by fungi
that invade entrance holes. Plantation trees occasionally are deformed or
killed. In nurseries, losses average about 12% from culling of infested
cuttings (Cook and Solomon 1976).
Control. Woodpeckers are one of the most important natural
enemies of the cottonwood clearwing borer, particularly of overwintering larvae,
but the holes they excavate may aggravate infestations by providing more
oviposition sites and entrance courts for fungi (Cook and Solomon 1976).
The parasite Apanteles paranthrenidis Muesebeck has been recorded, but
nothing is known of its effectiveness (Marsh 1979). In heavily infested
nurseries, the rootstocks should be rouged out and burned about every 3 years to
destroy the borers (Solomon 1988a). Systemic insecticides incorporated
into soil provide some control (Cook and Solomon 1976).
Adult(s) female. James Solomon,
USDA Forest Service. |
Damage stem with frass. James Solomon,
USDA Forest Service. |
Larva(e) and gallery. James Solomon,
USDA Forest Service. |
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