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HOST: All Pines
IMPORTANCE: The southern pine
beetle is considered the most destructive forest insect in the South. Weakening of the
trees by flooding, windstorms, and especially drought commonly precedes these outbreaks.
Trees of all sizes are attacked, but usually those larger than six inches are infested
first. A few trees to several thousand will be killed in spots or patches.
DESCRIPTION OF THE INSECT: The
brown to black beetle is about 1/8 inch long. Its hind end is rounded, in contrast to the
scooped out posterior of Ips beetles. The larvae are white with a reddish-brown head and
the pupae pure white. Fully grown larvae and pupae are approximately 1/8 inch in length.
The eggs are white, and very visible to the eye.
SIGNS OF ATTACK: The first
indication of attack is usually the yellowing or browning of the needles. Examination of
the trunk of the tree will usually reveal white, yellow, or sometimes red-brown pitch
tubes, about as large as a wad of gum. Under unusually dry weather conditions, pitch tubes
may be very small or absent and only reddish-brown boring dust will be present.
Examination of infested trees by removal of the bark will show a distinctive winding
"S" shaped gallery pattern. This pattern is quite different from the
"Y" or "H" shaped gallery pattern of Ips beetle and is a good
identification characteristic if no adults are present. Active spots or patches of
infestation are distinctive also in that the center trees have dark reddish-brown foliage
gradually changing until those on the edge have light greenish or yellowish green foliage.
HABITS: The adult beetles are
usually attracted to weakened trees. In epidemics, however, they attack trees that appear
to be healthy and vigorous. Initial beetle attacks are in the mid-trunk area and then up
and down the length of the tree. The adult beetles bore through the bark and then excavate
long winding "S" shaped galleries. Eggs are laid in niches along these
galleries. The larvae feed in the cambium area until they are grown and then excavate
cells in which to pupate near the bark surface. After pupation the adult beetles chew
through the bark and emerge. The complete life cycle of the attack, takes from 25 to 40
days to complete, depending on the temperature.
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