Southern Pine Beetle Population Dynamics in TreesThis article is part of a larger document. View the larger document here.
Successful mass attack of a pine tree by the southern pine beetle (SPB) results in the tree’s death and provides opportunity for colonization of the new phloem resource and reproduction by a new generation of SPBs plus hundreds of associated species of insects, mites, fungi, and nematodes. The within-tree portions of the SPB life history can be divided into component processes of colonization (including attack, mating, gallery construction, and oviposition), parent adult reemergence, brood development and survival, and emergence of a new generation of adults. Variables considered in relation to the attack process are threshold density needed to overcome tree resistance, spatial distribution of attacks on trees, rate of attack through time, attack density, and tree resistance to attack. Southern pine beetle females that successfully colonize pine phloem select a single mate, construct galleries in phloem, and oviposit eggs along the margins of those galleries. After oviposition, a variable, and frequently high, proportion of parent adults reemerge and are then available to colonize additional hosts. The reemergence process is strongly influenced by temperature but weakly by parent adult density. Within-tree development of the new SPB brood proceeds in the phloem from egg hatch through four larval stages, the last being completed in a cell in the outer bark in which pupation occurs. Pupae become callow (teneral) adults, then brood adults that subsequently emerge to colonize new hosts. Withintree development is strongly influenced by temperature, season of the year, SPB density, fungi (both beneficial and antagonistic), and mortality from a variety of predaceous and parasitic species. The effects of temperature on development, and to a lesser extent mortality, have been described. Estimation of the amount of mortality to within-tree populations is difficult to accurately measure, and it is even more challenging to identify and quantify causes of stage-specific mortality.