Multiple intensive black cutworm moth captures, 9 or more caught over a 2-night period, around April 12, signaled for us to begin tracking heat units (Base 50), see “Black Cutworm Pheromone Trap Report.” Based on the black cutworm’s growth development model, it takes approximately 300 heat units (base 50ºF) from egg hatch to early 4th instar; this is when black cutworm larvae begin to cut plants. Some minor leaf injury may be present before then.
In referring to the accompanying temperature accumulation map, the southern third of Indiana is currently at, or above, 300 degree days. With forecasted warmer temperatures, soon all of southern Indiana should be scouting for black cutworm feeding/cutting in high risk corn. Unfortunately, less than 10% of the corn is planted, and weedy fields for egg laying are abundant for continual moth arrivals. Consider the timing of corn emergence, yet to be planted, and the progression of cutworm development in the next week or two.
Happy scouting!
Black cutworm instars (i.e. size) 2 through 6, 4th instar is left of the penny.
