Ohio State University's western bean cutworm catches sharply increased last week, with many of the adults being caught in northwest Ohio.
Although it's difficult to use trap counts to predict damage, a general rule of thumb recommends scouting for egg masses when multiple moths are caught over consecutive nights.
A few traps are averaging more than 1 moth caught per night, so egg scouting should begin. To look for WBC eggs, inspect 20 corn plants in 5 random locations. Inspect the upper 1-2 most leaves because WBC prefer to place eggs on leaves that are more vertical in orientation.
WBC egg masses start out as white, and are laid in clumps of 25-100. As they mature, the eggs turn tan, and then dark purple. Egg hatch should occur within 24-48 hours once the eggs turn purple. Economic threshold is recommended when 5% or more of inspected corn have an egg mass.
Although the university is seeing increased catches, we are probably not at peak flight just yet. Therefore, they recommend scouting for eggs at least until past peak flight (i.e., when the numbers decrease from the previous week).
Because of the heat, we may see peak flight soon, possibly during the 2nd week of July. If high numbers of WBC egg masses are found, please contact state entomology specialists or local extension educators (we are in the need for egg masses for efficacy work).
In Pennsylvania, Penn State University Extension and the Department of Entomology are trapping for western bean cutworm. Pheromone traps have been deployed in approximately 20 counties to search for moths of this species.
This potential pest of corn and dry and snap beans was found for the first time in Pennsylvania in 2009 when we found approximately 90 moths distributed across the state. In 2010, we found nearly 370 moths across Pennsylvania, but two-thirds of these moths were concentrated in Erie County and the northwestern part of the state.
In 2011, the university found 350 moths, but the population center shifted eastward so that most moths were found in Centre, Lycoming, and Tioga Counties.
Thus far in Pennsylvania, the university has captured small number of moths in Berks, Bucks, Dauphin, Lebanon, and York Counties.
Researchers will continue to track populations and notify growers of where large populations are found. Importantly, in Pennsylvania researchers have only detected a single larval infestation in corn ears (Centre County), so based on the information we have the economic risk posed by this pest in Pennsylvania appears low, but the university doesn't want to be caught off guard by this pest species, which is distributed across the state.
In Indiana, Michigan, and Ontario this pest is causing economic damage, so we continue to tracks its populations in Pennsylvania to see how severe of a pest it might be in our fields.
See this Web page for details on this pest and a summary of trapping efforts for last year: http://ento.psu.edu/extension/field-crops/corn/western-bean-cutworm.