Influence of Phloem Moisture on Brood Development of the Southern Pine Beetle (Coleoptera: Scolytidae)

Abstract

Phloem of loblolly and shortleaf pine trees attacked by the southern pine beetle, Dendroctonus frontalis Zimmerman, exhibited a characteristic drying followed by rehydration. Trees With initially higher phloem moistures retained relatively higher levels during drying following attack. Limited population estimates suggested that brood survival was lower in trees with high moisture. In the laboratory, rearing bolts which were waxed to maintain higher phloem moisture had lower beetle survival than unwaxed bolts. High phloem moisture was associated with the formation of long larval mines, instead of feeding chambers, which in turn led to lowered survival. Emergence of the survivors was positively correlated with phloem moisture, suggesting that high moisture was beneficial to larvae and pupae in the outer bark.