John P. Jones
A decline in loblolly pine, first reported in Bogalusa, La., in 1966, helped trigger a long-term study at the LSU AgCenter. At first, it was suspected that it was the same disease as littleleaf disease of shortleaf pine, which was attributed to site factors and Phyphthora cinnamomi, a water mold. However, other studies led us to suspect Leptographium species might also be involved. We implemented a study to determine the respective roles of P. cinnamomi, Leptographium species, root attacking insects and various site factors. Preliminary data indicate that P. cinnamomi do not significantly correlate with decline symptoms, but Leptographium species correlate with symptoms and are probably the major pathogens involved. We have also found that Leptographium can routinely be isolated from many of the beetles and weevils that occur on pine roots and the soil around the roots. Our data indicate that loblolly decline results from an imbalance in the complex interrelationships involving insects, pathogenic fungi and the pine itself. We are now analyzing soil samples for physical and chemical characteristics that may affect the course of the decline. We are also conducting various inoculation experiments to confirm the ability of insects to vector Leptographium and to confirm that it is pathogenic to loblolly pine. The information developed from this research will help policy makers with the decisions that will determine the nature of southern forests for the next 100 years.
John P. Jones, Professor, Department of Plant Pathology and Crop Physiology, LSU AgCenter, Baton Rouge, La.
(This article was published in the summer 2002 issue of Louisiana Agriculture Magazine.)
The LSU AgCenter and the LSU College of Agriculture