By Blake Jackson
Penn State Extension and the Department of Entomology are once again tracking black cutworm activity across Pennsylvania using pheromone traps to help farmers monitor potential threats to corn crops this spring.
Researchers use the traps to detect significant flights of black cutworm moths, which occur when eight or more moths are captured over two consecutive nights. These flights signal an increased risk of caterpillar damage later in the season.
So far, the only confirmed significant flight has been recorded in Guilford Township near Chambersburg in Franklin County. The first major moth flight in that area was detected on April 7.
Since then, the region has accumulated roughly 220 growing degree days, bringing it closer to the estimated 300 degree-day threshold when cutting damage is likely to appear in corn fields. Based on current conditions, experts expect scouting for black cutworm injury near Chambersburg should begin around May 20.
Additional significant moth flights were also recorded later in April in the same region, suggesting the risk of damage may continue beyond late May.
Extension specialists caution growers against adding insecticides to herbicide applications as a preventive measure. They say spraying without understanding local cutworm pressure is unlikely to provide economic benefits and may not accurately explain the absence of crop damage.
Black cutworm caterpillars can injure corn plants from emergence through the V4 growth stage, although damage after V5 is uncommon. Early feeding injury may appear as rows of small, symmetrical holes in leaves.
Economic treatment thresholds vary by crop stage, ranging from two cut plants per 100 seedlings to seven cut plants per 100 V4-stage plants.
If damaging populations are confirmed during scouting, experts recommend rescue treatments as the most effective and economical management strategy.
Photo Credit: jeff-graybill
Categories: Pennsylvania, Crops, Corn