APS Homepage

POSTERS: Pathogen-vector/insect interactions

Lonsdalea quercina occurs on insects visiting drippy blight diseased oak trees
Rachael Sitz - US Forest Service. Jane Stewart- Colorado State University, Whitney Cranshaw- Colorado State University, Ned Tisserat- Colorado State University, Vincent Aquino- University of Colorado

Drippy blight is a recently recognized disease of red oak trees caused by the bacterial pathogen Lonsdalea quercina in conjunction with the kermes scale insect Allokermes galliformis. The name drippy blight is descriptive of the disease, as copious amounts of bacterial exudates occur at kermes scale feeing sites throughout the canopy. Their combined damage causes branch abscissions and limb dieback, which over time results in progressive canopy thinning and tree death. Although the majority of damage occurs at kermes scale feeding sites, these insects are relatively immobile and not likely involved in long-distance dispersal of the bacterium. However, the associated bacterial exudates are visited by a variety of arthropods that may become contaminated with the bacterium. In order to test for natural dissemination of L. quercina on the arthropod community, trapped specimens were tested for bacterial contamination using DNA extraction and PCR protocols with species specific primers. Furthermore, collections were made of arthropods actively visiting trees. These arthropods were assayed on nutrient agar, and the resulting cream colored bacterial colonies were identified using colony PCR. Overall, 158 arthropod samples were tested over two field seasons, with eight percent carrying the bacterium. Contaminated specimens exhibited differing life histories and were from three insect orders and eight families. Insects in the order Hymenoptera (including ants, bees, and wasps) were the most frequently contaminated, but a variety of insects likely play a role in the spread of disease.