This post is based on an article written for Cornell’s WHAT’S CROPPING UP blog by Ken Wise (NYS IPM) and Mike Hunter (CCE North Country Regional Ag Team) with editing by NYS IPM’s Jaime Cummings and Marion Zuefle.
Western bean cutworm (Striacosta albicosta) aka WBC was first discovered in New York State in 2009. This insect pest of corn and dry beans can cause significant yield and quality losses to field corn grain.
The Western bean cutworm moth (Photo by: Adam Sisson, Iowa State University, Bugwood.org)
The adult moth lays eggs on the upper surface of leaf just before tasseling. White eggs turn tan, and then a purplish color before hatching (Fig. 2). Tiny and protected1st instar larvae feed on their own egg shell before moving on to leaves, pollen and silk. (Fig. 3). 4th instars bore into the corn ear to feed on kernels (Fig. 4), and here’s the big difference between WBC and other worm pests (European corn borer, corn ear worm): multiple worms in one ear. Matured larvae drop to the soil surface, then burrow down to overwinter in a pre-pupa stage (Fig. 5). They complete pupation in late spring and emerge from the soil from mid-July through mid-August. The adult moths fly and mate during late July to early August.
Figure 2: Eggs are white when first laid and then turn purplish before hatching (Photo by Mike Hunter, CCE)
Figure 3: First instar Western Bean Cutworm larvae (photo by Mike Hunter, CCE)
Figure 4: Mature Western Bean Cutworm Larvae (Photo by Ken Wise, NYS IPM)
Figure 5: Soil chambers created by Western bean cutworm larvae- (Photo by Keith Waldron, NYS IPM)
Figure 6: Western Bean Cutworm Lifecycle
In 2010, we developed a WBC pheromone trap monitoring network. Each year, from late June through August, this network of CCE Educators, crop consultants and agricultural professionals place out bucket pheromone traps. A female WBC pheromone lure attracts and catches only the males. Each week they are counted and reported (along with location of the trap) to determine when scouting should occur. This, however, doesn’t determine if or when a field should be sprayed with an insecticide.
Since 2010, the population of the WBC in New York has increase exponentially. Likewise, we started with 19 volunteers and 44 traps in 29 counties, and in 2018, we had 50 volunteers and 118 traps in 45 counties.
Table 1. New York Western Bean Cutworm 2010 – 2018 Collection Data Summary*
Includes traps in field corn, sweet corn and dry beans
Average captures by trap went from 15 in 2010 to 333 in 2018. Northern NY is the hot spot for WBC—some traps had almost 3000 in a single trap.
Figure 8: Average Western Bean Cutworm Moths Caught in Traps Weekly (Includes traps in field corn, sweet corn and dry beans)
A very important aspect of managing WBC is knowing when peak flight occurs. This generally ranges from the last week in July to the first week in August. Because females prefer to lay eggs in pre-tassel corn, growers can determine when to be vigilant about scouting for WBC egg masses and small larva.
Figure 9: Average Moth Counts/Trap without Northern NY (Includes traps in field corn, sweet corn and dry beans)
The data suggests the population is beginning to build up in previously low-count areas of the state. In time, management of WBC populations will likely be needed across the state. Widespread, high WBC populations in Northern NY have resulted in insecticide treatments.
While WBC damage to corn ears can be significant and may have detrimental effects on corn grain yield and quality, the economic impact on corn silage is less understood. For more on this read the full report.
No matter what 2019 brings, the NY WBC Pheromone Trap Monitoring Network will be watching!
Livestock & Field Crops IPM Extension Area Educator, housed at CCE Dutchess County, Millbrook, NY
2018 New York WBC Pheromone Trap Monitoring Network: Thanks to cooperating growers for allowing us to use their fields for sample sites. Special thanks to the following individuals for their enthusiasm, dedication, excellent data collection and maintenance of the WBC trap network: Adam Abers, Brian Boerman, Chuck Bornt, Elizabeth Buck, Sara Bull, Paul Cerosaletti, Mike Davis, Janice Degni, Dale Dewing, Natasha Field, Cassidy Fletcher, Jennifer Fimbel, Aaron Gabriel, Kevin Ganoe, Jeffrey Gardner, Don Gasiewicz, John Gibbons, Ethan Grundberg, Mike Kiechle, Ariel Kirk, Jeff Kubeka, George Krul, Christy Hoepting, Mike Hunter, Amy Ivy, Joe Lawrence, Jodi Lynn Letham, Jen Masters, Laura McDermott, Carol MacNeil, Sam Meigs, Stephanie Melancher, Sandy Menasha, Jeff Miller, Anne Mills, Eric Nixon, Kitty O’Neil, Jessica Prospers, Bruce Reed, Teresa Rusinek, Erik Kocho-Schellenberg, Jack Steele, Abby Seaman, Keith Slocum, Paul Stackowski, Mike Stanyard, Dan Steward, Crystal Stewart, Allie Strun, Linda Underwood, Katherine Vail, Ken Wise, Anastasia Yakaboski, Glenn Yousey, Marion Zuefle, WNYCMA. The WBC Bt corn trials were made possible with support from both the New York Corn Growers Association and the Northern New York Agricultural Development Program.