upper leaf surfaces of understory vegetation (fig. 160B). The female is joined in the 
chamber by a male and after mating she begins construction of a gallery diagonally 
across the grain of the wood, etching the surface of the wood faintly. The direction 
of the gallery eventually is reversed, thus creating a typical S-shaped or serpentine 
pattern (fig. 160C). Eggs are deposited at intervals of 3 to 25 mm or more in niches 
in each side of the gallery, one egg per niche. Hatching occurs in 3 to 9 days, and 
the larvae tunnel away at right angles to the gallery. Young larvae initally produce 
threadlike mines which are visible when the inner bark is exposed. As the larvae 
continue to develop, they mine outward into the corky bark where they construct 
individual cells in which to pupate. Each adult bores its own emergence hole. All 
the adults in a given brood may emerge during a period of 10 to 32 days. Three to 
five generations develop each year in western North Carolina. In Virginia and West 
Virginia, four generations and a partial fifth occur; in the Deep South there are as 
many as seven per year. 
Newly emerged beetles may attack adjacent trees or they may fly to stands some 
distance away. Trees under 15 years of age and less than 5 cm in diameter are rarely 
attacked. When outbreaks develop, scattered groups of pines growing under dense 
stand conditions, disturbed by recent logging or lightning damage, or on sites 
subjected to moisture stress and disease are attacked. Once an epidemic is under- 
way, stands of all age classes and densities are vulnerable. Spot infestations, which 
may range from a few trees to stands occupying hundreds of hectares, are charac- 
terized by a central zone of defoliated trees, one or more adjacent areas of red- 
topped trees, and one or more peripheral fingers of infested trees with yellowish or 
green foliage extending out into the surrounding forest. The needles of pines 
infested during midsummer turn yellow in 2 or 3 weeks and reddish brown in 4 to 6 
weeks. Death results either from the girdling of the main stem by the beetle or from 
the effects of the blue stain fungus, Ceratocystis minor (Hedgc.) Hunt, which the 
beetles introduce into the tree. 
Southern pine beetle outbreaks appear to be caused by conditions that reduce tree 
or stand vigor, whether by natural phenomena or human intervention. Drought or 
flooding, overstocking, stand disturbance and site depletion are most often associ- 
ated with initial infestations. Beetle populations increase rapidly in response to 
favorable host and environmental conditions and cause extensive damage. Only in 
the more northerly or high elevation areas of the insect’s range do low winter 
temperatures serve as a check in terminating outbreaks (73). A return to more 
favorable growing conditions tends to be associated with reduced beetle activity 
over large areas. 
Management practices designed to improve and maintain the vigor of stands 
(e.g., timely thinning), and the removal of high-risk trees, such as those injured by 
recent logging, struck by lightning, or attacked and weakened by other insects, are 
helpful in reducing losses. Once an outbreak is underway, the salvage or chemical 
treatment of infested trees may be helpful in suppressing populations. To be most 
effective, these practices must be applied on a timely basis with first priority given 
_to larger spots that have a greater volume of actively infested trees. 
Several reviews of the life history and habits, natural enemies and associated 
organisms, sampling and population dynamics, impacts, utilization, site, stand, 
and climatic factors affecting stand susceptibility and vulnerability, silvicultural 
and direct control methods and materials have been issued (56, 87, 107, 246, 247, 
Dope SLO FOLD 35, 40, :/00, 1155, 41803. 1195). 
345 
