A new disease, laurel wilt, was diagnosed in southwestern Kentucky in the summer of 2019, and it has the potential to rapidly kill sassafras trees.  The area around Trenton in southern Todd County appears to be the area worst affected at this time.  Laurel wilt is a fungal disease caused by the invasive pathogen Raffaelea lauricola.  The disease is transmitted by the wood-boring redbay ambrosia beetle; which prior to the diagnosis of laurel wilt in this area, was only known to exist hundreds of miles to the south and southeast of Todd County.  The long-distance spread of the disease to Kentucky from where it was previously known is likely due to human movement of beetle-infested wood, as opposed to a spread of the disease by natural movement of its insect vector.

In addition to working with local homeowners and landowners to identify the cause of their dying sassafras trees, I have conducted several educational efforts to inform others about laurel wilt.  I wrote an article for the local newspaper which included information and photos of infected sassafras trees.  I conducted a training at the September 2019 District 7 Staff Meeting; providing agriculture and horticulture agents with a publication I created containing information and photos of various stages of the laurel wilt’s effects on sassafras trees.  I also conducted a training on laurel wilt for about 40 agriculture professionals at the Commercial Pesticide Training class in Paducah in December.  Most of the people reached through these educational efforts had never heard of laurel wilt and had no knowledge of it’s devastating effect on sassafras trees.     

 In Kentucky, sassafras is likely to be the species most affected by laurel wilt, although the disease can affect a range of plants in the Lauraceae family, including spicebush (which is Kentucky’s other laurel species).  At this time, scientists have not seen any signs of disease resistance in Kentucky’s sassafras population; which means that all the state’s sassafras trees could potentially die if the disease spreads out of this area and into the rest of the state.

State forestry specialists don’t know the extent to which laurel wilt disease has already spread in Kentucky.  So far, the disease has been positively confirmed only in Todd, Logan, and Christian Counties.  A major unknown affecting the potential spread of this disease is the issue of the winter-hardiness of the redbay ambrosia beetle.  It was originally confined to the range of the redbay trees in the low country of South Carolina and Georgia; but it has proven that it can survive and reproduce in southwestern Kentucky.  The big question now is:  how will the redbay ambrosia beetle adapt to the climatic conditions in the central, northern, and eastern areas of the Bluegrass state?