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Ambrosia Beetles and Bark-Colonizing Weevils Carry Thousand Cankers Disease Fungus

Photo of Thousand Cankers Disease affected eastern black walnut trees used to determine insects emerging and carry the TCD fungus. Jennifer Juzwik, U.S. Department of Agriculture Forest Service.Thousand Cankers Disease affected eastern black walnut trees used to determine insects emerging and carry the TCD fungus. Jennifer Juzwik, U.S. Department of Agriculture Forest Service.Snapshot : Thousand cankers disease (TCD) is a threat to the health of eastern black walnut, a highly valued species for timber and nut production in the eastern United States. Two ambrosia beetle species and a bark colonizing weevil species were found to carry the TCD fungus, in addition to the previously known walnut twig beetle that carries and transmits the fungus to healthy trees. These findings are important to the state and federal monitoring and management efforts for this disease.

Principal Investigators(s) :
Juzwik, Jennifer 
Research Location : Urban landscapes in Hamilton, Ohio (Butler County)
Research Station : Northern Research Station (NRS)
Year : 2016
Highlight ID : 1123

Summary

Thousand cankers disease (TCD) has caused dieback and death of eastern black walnut (Juglans nigra) in urban areas of the United States. Walnut timber and nut producers are greatly concerned about potential losses due to this emerging disease. A Forest Service scientist, in collaboration with partners at Purdue University, collected ambrosia beetles, bark beetles, and weevils colonizing main stems and branches of J. nigra trees exhibiting TCD symptoms in Ohio. Collected insects were identified and then evaluated for the presence of the TCD canker causing fungus, Geosmithia morbida, on their bodies. Two ambrosia beetle species (Xylosandrus crassiusculus and Xyleborinus saxeseni) and one weevil species (Stenominus pallidus) accounted for 149 of 155 collected specimens. G. morbida was detected on 22 to 65 percent of the individuals of these three species, as well as on two emerged walnut twig beetles (Pityophthorus juglandis). The latter species was previously the only known carrier of the fungus. The fungus-carrying ambrosia beetles may exacerbate TCD progression on J. nigra in affected areas. Additional insect species carrying G. morbida may expand the distribution of the G. morbida beyond those areas reached by WTB. Options for monitoring these additional species are under consideration by several eastern states.

Forest Service Partners

External Partners

 
  • Purdue University

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