- Recent storm systems have brought black cutworms along for the ride.
- Timing of scouting can be improved by tracking heat unit accumulations, combined with pheromone trap catches.
- Scouting fields and treating when necessary is more reliable than preventative applications of insecticides.
- Don’t rely on insecticide-treated seed to prevent economic damage.
Many of our dutiful trapping cooperators throughout the state captured black cutworm moths this past week – refer to the “Black Cutworm Adult Pheromone Trap Report” for captures. This recent flush of moths is attributed to storms that have kept us out of the fields.
Moth arrival, along with the use of heat units to predict the beginning of larval activity, gives us an indication of the potential severity of the problem and locations of concern. Thus, we are able to predict with some degree of accuracy when and where crop damage is most likely to occur based on this information.
Here’s a question we are often asked: Should one treat for black cutworm before or at planting? Because of the sporadic outbreak nature of this pest, the tried, true, and economic approach to black cutworm management is to scout fields, determine infestation and damage levels, and use a rescue treatment, if needed. Foliar insecticides are effective, especially when applied early (i.e. while cutworms are small and not yet “cutting”).
Producers using insecticide-treated seed may have a false sense of security concerning black cutworm control. The systemic activity of these insecticides during the seedling stage should help suppress small larvae feeding on plants. Larger larvae, as with all insects, are more difficult to kill. Coupled with the fact that there is less insecticide in plant tissues at this time, efficacy declines as the spring wears on. The black cutworm flight and egg-laying period spans several weeks and green or weedy fields may attract egg-laying moths over multiple flights. These fields can experience significant damage and stand losses, even when treated seed is used.