Hardwood platypus
Platypus compositus (Say)
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. Oak, hickory, pecan, chestnut, poplar, birch, beech, elm,
basswood, sweetgum, magnolia, persimmon, willow, maple, cherry, tupelo,
baldcypress. Prefers oak, hickory, maple, and beech, but other hosts are
also commonly attacked (Beal and Massey 1945, Chamberlin 1939).
Range. Primarily a tropical and subtropical species, extending
through Central and South America and Mexico into Texas east to Florida and
northward from southern Missouri to southern New York (Atkinson 1989, Beal and
Massey 1945, Blackman 1922, Hubbard 1897). Most common and widely
distributed Platypus sp. in the United States; most common in the South,
particularly along the Gulf Coast.
Description
Adult. Large, very elongate, cylindrical, reddish brown ambrosia
beetle, 4.3 to 5.0 mm long, about four times as long as wide (Arnett 1968,
Atkinson 1989, Beal and Massey 1945, Blackman 1922, and Hubbard 1897).
Head visible from above, as wide as pronotum, noticeably broad and flattened in
front. Pronotum finely, shallowly, and sparsely punctured, longer than
wide, with two tiny margined pits just behind the middle of both sexes.
Elytra elongate with punctate striae. Elytral declivity in males prolonged
into heavy process that bears three teeth on their tips; truncate and unarmed
(toothless) in females.
Egg. Elongate to oval, pearly white, clear to opaque, 0.72 to
0.89 mm long, 0.41 to 0.48 mm wide.
Larva. Elongate, fleshy, subcylindrical, nearly straight to
slightly curved, white to creamy white, with prominent chitinous ridges dorsally
on prothorax, 4.8 to 6.4 mm long.
Biology. Adults are active throughout the growing season from
spring to October or November (Blackman 1922, Chamberlin 1939, Doane and others
1936, Hubbard 1897). Adults are attracted to declining host trees,
particularly those with fermenting sap. Males initiate the galleries; each
male is soon joined by one female. The males are aggressive fighters and
frequently battle over females. The beetles produce deep galleries in the
sapwood and heartwood. Females deposit 100 to 200 eggs in loose clusters
of 10 to 12 in the galleries. Larvae feed entirely on ambrosia fungus
(brought to new sites by parent beetles) that grows prolifically on moist
gallery walls. Larvae wander freely in the tunnels as they feed and
grow. They can move rapidly within the tunnels, but they do not damage or
destroy eggs and small larvae along the galleries. Larvae require 5 to 6
weeks to develop. When nearly mature, the larvae help to extend the
galleries, but they do not consume the wood. To pupate, mature larvae
construct deep cradles above and below the feeding galleries; pupation occurs in
these cradles, and newly transformed adults emerge
from the host through entrance holes made by the parent beetles. There are
three to four generations per year in the Gulf Coast region.
Injury and Damage. The pest seldom attacks healthy, vigorous
trees but rather limits its attacks on living trees on those weakened from
drought, disease, old age, insect defoliation, wounding, and other factors that
produce serious stress (Chamberlin 1939, Craighead 1950, Hubbard 1897). It
prefers severely weakened and dying trees, fresh-felled trees, and logs full of
moisture. Larger trees in the pole- and sawtimber size classes are favored
over smaller trees. Whitish, fibrous boring dust is often present in bark
crevices around the entrance holes. During periods of plentiful moisture
and high humidity, the borings may stick together as they are pushed out to form
compacted, stringlike strands; the white borings sometimes accumulate in loose
piles around the base of infested trees. Dissection reveals a simple but
extensive gallery system that often penetrates deep into the sapwood and
sometimes into the heartwood. In some trees and logs where the moisture
level remains favorable, the galleries may branch and rebranch several times,
and sometimes follow the growth rings. Numerous short, vertical pupation
cells or cradles may be present above or below the galleries. Galleries
and cradles are stained black by fungi growing on the gallery walls.
Beetles do not kill trees but may hasten the death of severly weakened
ones. The most serious damage caused by this insect is the extensive
black, fungus-stained galleries that penetrate the sapwood and heartwood.
This insect, one of the most destructive ambrosia beetle species in the logging
and lumbering industry, can, in a few weeks, render wood worthless for lumber.
Control. Preventive measures, such as keeping trees vigorous and
preventing wounds, are the best means of minimizing damage to living
timber. In the Deep South, trees felled between April and October should
be removed from the woods and processed within 2 to 3 weeks (Craighead
1950). If green logs cannot be milled promptly, they should be either
stored under water, sprayed continuously with water, or sprayed with a
protective insecticide. Trap trees with girdling and destruction properly
timed have been used with some success in high-risk areas (Blackman 1922).
Damage boring and associated staining. W.H. Bennett,
USDA Forest Service. |
Adult(s) male. Gerald J. Lenhard,
Louisiana State University. |
Adult(s) female. Gerald J. Lenhard,
Louisiana State University. |
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