Hardwood Platypus
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Solomon, J.D. 1995. Guide to Insect Borers in North American Broadleaf Trees and Shrubs. Agriculture Handbook 706. Washington, DC. United States Department of Agriculture, Forest Service. 735 p.
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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).
Gallery
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