Temporal Relationship Between Southern Pine Beetle (Coleoptera: Scolytidae) and Pinewood Nematode Infestations in Southern Pines

The incidence of feeding scars of the cerambycid vectors of the pinewood nematode (Bursaphelenchus xylophilus (Steiner and Buhrer) Nickel) on twigs of loblolly (Pinus taeda L.) and shortleaf (Pinus echinata Mill.) pines in central Louisiana was determined. Feeding scars on twigs taken from pines felled at random were compared to those on twigs taken from pines adjacent to southern pine beetle (Dendroctonus frontalis Zimmermann) infestations. Additionally, the presence of pinewood nematode in trees attacked by southern pine beetle was followed through the course of beetle development. Significantly more cerambycid feeding scars were present on twigs of trees located near the advancing edge of a southern pine beetle infestation than on twigs not adjacent or near any known southern pine beetle infestation. From 82 to 100% of the trees sampled adjacent to bark beetle infestations had been fed upon by cerambycids. Pinewood nematodes were recovered from 79% of these trees. The incidence of nematodes in the boles of trees attacked by southern pine beetles increased as immature beetles entered their later instars. The highest incidence of nematodes was from trees recently vacated by southern pine beetles. Trees killed by the southern pine beetle may thus serve as reservoirs for the pinewood nematode and its cerambycid vectors and lead to the infestation of adjacent trees and facilitate subsequent SPB colonization.