Harvey’s works with Michigan State University’s Entomology Department to report Western Bean Cutworm catches.
WBC traps are erected and checked regularly by Harvey’s scouts every year. In 2009, the trap catch numbers led to the Michigan State University Entomology Department issuing a must-spray drybeans warning for the entire Montcalm county.
Background
Western bean cutworm (WBC) is a late season corn ear pest. Beginning in the early 2000s, WBC expanded eastward across the United States. In 2006 the first WBC were found in Michigan. Over the next several years WBC populations increased and economically damaged crops became more prevalent.
Damage
Larvae feed on tassel pollen if present. While larvae mature and tassels are not as fresh, larvae move down plant to feed on silks and kernels. Primary damage consists of kernel feeding. WBC do not cannibalize which means multiple larvae may feed on the same ear. Secondary pests and pathogens enter the plant by way of husk feeding.
Life cycle
WBC has one generation a year with six or seven larval stages. WBC overwinter four to ten inches below the soil in pre-pupa stage. Pupation occurs in late May to early June. Adult moths emerge in early July. Peak flight will occur when half the season’s WBC population emerges at 1,422 growing degree-days (Base 50°F). Adults are brown and ¾ of an inch long. They can be identified by a white bar on the leading edge of the forewing, with a white dot and crescent behind the bar.
Scouting
Scouting should start following the accumulation of 1,320 growing degree-days (Base 50°F), or when pheromone trap catches increase in your area. Females prefer pre-tassel or just-tasseling corn. Egg masses are found on the top side of leaves in upper canopy, particularly the flag leaf or first leaf below tassel. Eggs are pearly white when first laid, and progressively turn darker shades over the course of a week before turning dark purple just prior to hatch. Eggs are most commonly laid in groups of 5-200 eggs, with the average being 50 eggs per mass. First instar larvae are brown with a black head and black markings down their backs. WBC larvae can be distinguished from corn borer by the two dark brown stripes behind the WBC’s heads.
Control
If over 5% of plants have egg masses or larvae, an insecticide application is encouraged. Application should be made before larvae reach the ear, or when 95% of tassels are emerged. Yieldgard Bt corn WILL NOT control WBC; however Agrisure Viptera and Herculex Xtra Corn Borer traits DO provide WBC control. WBC infestations are patchy across the landscape, thus using Herculex Xtra Corn Borer or Agrisure Viptera traits may increase cost in fields that remain below threshold however in presense of Western Bean Cutworm using traits is more effective than an insecticide application (Control options courtesy of MSU Entomology Dept).
Western Bean Cutworm
Harvey’s works with Michigan State University’s Entomology Department to report Western Bean Cutworm catches.
WBC traps are erected and checked regularly by Harvey’s scouts every year. In 2009, the trap catch numbers led to the Michigan State University Entomology Department issuing a must-spray drybeans warning for the entire Montcalm county.
Background
Western bean cutworm (WBC) is a late season corn ear pest. Beginning in the early 2000s, WBC expanded eastward across the United States. In 2006 the first WBC were found in Michigan. Over the next several years WBC populations increased and economically damaged crops became more prevalent.
Damage
Larvae feed on tassel pollen if present. While larvae mature and tassels are not as fresh, larvae move down plant to feed on silks and kernels. Primary damage consists of kernel feeding. WBC do not cannibalize which means multiple larvae may feed on the same ear. Secondary pests and pathogens enter the plant by way of husk feeding.
Life cycle
WBC has one generation a year with six or seven larval stages. WBC overwinter four to ten inches below the soil in pre-pupa stage. Pupation occurs in late May to early June. Adult moths emerge in early July. Peak flight will occur when half the season’s WBC population emerges at 1,422 growing degree-days (Base 50°F). Adults are brown and ¾ of an inch long. They can be identified by a white bar on the leading edge of the forewing, with a white dot and crescent behind the bar.
Scouting
Scouting should start following the accumulation of 1,320 growing degree-days (Base 50°F), or when pheromone trap catches increase in your area. Females prefer pre-tassel or just-tasseling corn. Egg masses are found on the top side of leaves in upper canopy, particularly the flag leaf or first leaf below tassel. Eggs are pearly white when first laid, and progressively turn darker shades over the course of a week before turning dark purple just prior to hatch. Eggs are most commonly laid in groups of 5-200 eggs, with the average being 50 eggs per mass. First instar larvae are brown with a black head and black markings down their backs. WBC larvae can be distinguished from corn borer by the two dark brown stripes behind the WBC’s heads.
Control
If over 5% of plants have egg masses or larvae, an insecticide application is encouraged. Application should be made before larvae reach the ear, or when 95% of tassels are emerged. Yieldgard Bt corn WILL NOT control WBC; however Agrisure Viptera and Herculex Xtra Corn Borer traits DO provide WBC control. WBC infestations are patchy across the landscape, thus using Herculex Xtra Corn Borer or Agrisure Viptera traits may increase cost in fields that remain below threshold however in presense of Western Bean Cutworm using traits is more effective than an insecticide application (Control options courtesy of MSU Entomology Dept).
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