Sudden Oak Drip Lonsdalea quercina is a bacteria condition currently affecting poplar and oak in California and Colorado. Its close relatives are in Europe but the conditions are understudied and little is known about them as although they are causing urban hazards, to date, they aren’t economic problems. They are problems for planting programs with red and pin oak, an urban nuisance with the “drips” landing on decking, and sidewalks and a hazard due to the death of large limbs.
Rachael Sitz, Plant Pathologist with the U.S. Forest Service, one of only a couple of researchers working with oak drip said, “Bacterial diseases can be difficult to detect and treat. Furthermore, in our global economy, we can easily purchase trees that originated in an area with a potential pathogen. Preventing the introduction of oaks or poplars from diseased areas into locations that do not have the pathogen is critical.”
“In Colorado, we see the combined damage of the scale insect (Allokermes galliformis) and the bacterium severely damaging our red oak trees, and when the trees have large dead limbs they become a hazard and are removed,” said Sitz. “This takes several years, so it is fairly slow, and our removals are of trees that are still trying to ‘hang on.’ It depends on the subspecies, but we know Lqq effects five species of oaks and their hybrids, and in Colorado Northern red oak seems more susceptible than other species of red oak. We are not sure of the host range yet, but globally we know of at least nine tree species affected by the four subspecies of Lonsdalea quercina.”
Researchers are still looking at how the bacteria is transferred. In one study, 14 species of insects tested positive for Lonsdalea quercina. These were from three insect orders (Coleoptera/beetles, Hemiptera/true bugs, and Hymenoptera/ants, bees, and wasps. A European paper noted bats are a transfer agent for the strains they are working with.
Sitz said, “Unfortunately, we do not have any good information about how to control this disease complex yet. Looking at other similar bacterial diseases, such as fire blight, may give insight on how to control the pathogen. Insects seem to be integral to the onset of diseases caused by L. quercina pathogens, so another option is to prevent insect damage when possible.