IPM BULLITEN

Penn State Extension in Franklin County has established a grid of eight trapping sites across the county to attempt to survey populations of black cutworm and true armyworm moths. We previously reported that true armyworm moths have been found in the St. Thomas area in large enough numbers to call for added scouting in that area. Now we have detected economically significant flights of black cutworm in the St. Thomas area. Growers in the vicinity and surround areas should be aware of a heightened risk to their corn fields. Note that corn fields planted following soybeans can often sustain heavier populations of black cutworm caterpillars.

Now that significant flights have been detected we can begin accumulating degree days. Cutting behavior of black cutworm caterpillars is expected 300 growing degree days after the significant flight. The Penn State Agronomy program in Franklin County has recently established a weather station in Chambersburg Pa and will be tracking growing degree days. This bulletin will be followed by another once we begin to approach the 300 growing degree days. When the second bulletin is received, folks should start scouting corn fields to look for cutting damage. Economic thresholds for treatment are 2, 3, 5, and 7 cut plants per 100 for seedling, V2, V3, and V4 respectively.

Treatment options for at-risk areas vary but can include higher rates of neonicotinoid seed treatments where corn has not been planted and planting lines of Bt corn with activity against black cutworm if seed is still needed; however, growers should recognize that neither of these options are completely effective. The most economical control method for cutworm is scouting fields and applying rescue treatments where cutting activity exceeds economic thresholds.

More information on this pest can be found online at http://ento.psu.edu/extension/factsheets/black-cutworm , or by visiting the local extension office. Please share this information with others who may be interested in it. Again it appears that the pressure at this point is limited to the greater St. Thomas area. I will continue to keep you up to date if populations build elsewhere.