Western Bean Cutworm Trap Counts in Blyth a Concern

We continue to monitor for western bean cutworm adults and egg masses at our trap locations. So far we have only found one egg mass (at the Glencoe site) and moth captures have been low, with the exception of our site in Blyth. To date we have captured 88 moths since the beginning of July at the Blyth site. Though this is still too low to be concerned about the bean crop in the immediate area (requires accumulation of 700 or more moths since the trap went up), I am concerned that there will be some damage in the corn fields in the area. I recommend that corn fields in the Blyth area are scouted this week and next to determine if enough egg masses are being deposited to warrant spraying. Tom Hunt (U of Nebraska) and Chris DiFonzo (MSU) recommend that the threshold be lowered somewhat, based on the damage that Nebraska has experienced in the past, even after following the original threshold. The recommended threshold that is being suggested is that a spray is warranted if 5% of the plants scouted (from 20 plants in 5 areas of the field) have egg masses or small larvae. If the eggs have hatched, spray at 95 percent tassel emergence or if tassels already emerged, when most of eggs are expected to hatch. It would be surprising if we reached threshold this year in Ontario but we should expect to see some ear damage in spots of some fields, particularly in the Blyth area.

Table 1. Western Bean Cutworm Trap Captures to Date in Ontario, 2008