When a Jefferson County Master Gardener displayed a plastic 2.5 gallon gasoline container peppered with round holes, it initially was a mystery. But the black spots turned out to be invasive beetles, Camphor Shot Borer beetles to be exact. Additional reports have come in from Wakulla County and another site near this one in Jefferson County.
In 2011, two Louisiana researchers reported this same behavior and speculated it might have been induced by the presence of ethanol in the gas.
The beetle Cnestus mutilatus (formerly Xylosandrus mutilatus) is indigenous to Asia and is one of twelve species of ambrosia beetles to have entered the U.S. since 1990. The most likely route of introduction was through solid wood packing materials such as pallets and crates.
The Camphor Shot Borer was first detected in Mississippi in 1999 and has since been found in West Virginia, Tennessee, Georgia, Ohio, North Carolina, Alabama and Texas in addition to Florida. According to Dr. Michael Thomas, taxonomic entomologist for the Florida Department of Agriculture and Consumer Services, it has not been determined to attack living plants in Florida. Other reports have found this pest in dying or severely stressed trees.
Camphor Shot Borers tunnels underneath the bark of their hosts, lay eggs and introduce a fungus which feeds the larvae once they hatch. While the female beetle introduces the fungus, it is the fungus, not the beetle that damages the host tree.
Females can fly one to three miles in search of a host. Reports list loblolly pine, dogwood, hop hornbeam, sweet gum, beech, china berry, black cherry, native plum and winged elm as targets for egg laying. As the name suggest, it also attacks the invasive camphor tree as well.
The long term effects of camphor shot beetles have yet to be determined, and there’s no standardized treatment for the pest. The International Plant Protection Convention has established protocols to monitor the movement of hardwood packing materials, but another invader has already established itself in our midst.