64 Nebraskaland • June 2020
MIXED BAG
In 2019, staff with the Nebraska Department of Agriculture
set 54 traps for walnut twig beetle in 11 counties across the
state. Traps were up from May through October, and samples
were collected from the traps every two weeks. Walnut
twig beetle specimens were collected from a single location
in Gering. This was the first find of walnut twig beetle in
Nebraska. All other traps in Nebraska were negative.
The beetle can carry the Geosmithia morbida fungal
pathogen that causes thousand cankers disease. The fungus
is particularly lethal to black walnut (Juglans nigra) trees.
Nebraska forests are home to more than 1.5 million black
walnut trees, which are all susceptible to this pest.
The number of beetles trapped at Gering were low, with
2-12 beetles per trap, collected over a six-week period in the
fall. Walnut trees near the traps are relatively isolated, and
other surveillance traps in the county did not collect any
walnut twig beetles. No obvious symptoms of thousand
cankers disease were observed in nearby walnut trees.
The NDA plans to continue to survey for the beetle across
the state in 2020. Trapping will occur statewide, with an
emphasis on Scotts Bluff and surrounding counties. The
NDA will also
set baited
branches in
Gering this
summer to
determine if
any beetles
found at a
location are
carrying the Geosmithia fungus. Walnut branches baited
with a lure will be suspended from a metal pole near black
walnut trees where the beetles have been previously trapped.
At the end of the survey, the branches will be de-barked to
collect any beetles that have infested the branches, and the
beetles will then be tested for G. morbida.
There are no changes to the Nebraska Thousand Cankers
Disease of Black Walnut quarantine at this time. Additional
information from the 2020 survey will be used to determine
if changes are necessary. For more information on the
Nebraska TCD quarantine, visit
https://nda.nebraska.gov/
plant/entomology/tcd_quarantine.pdf.
NEBRASKA WALNUT TWIG BEETLE UPDATE
By Julie Van Meter, State Entomologist
Nebraska Department of Agriculture
Adult walnut twig beetle (Pityophtoris
juglandis). STEVEN VALLEY, OREGON DEPARTMENT OF
AGRICULTURE, BUGWOOD.ORG
