Since the adoption of Bollgard cotton in North Carolina, damage from bollworms has decreased while stink bug problems have increased.
Jack Bacheler, North Carolina State University Extension entomologist, along with Extension agents, conducted the research from 1996-2003. Robeson County Extension Field Crops Agent Georgia Love prepared and presented the research at a recent field day.
The boll damage survey comes from randomly sampling 1,252 producer fields over the eight-year period.
The percentage of damaged bolls from bollworms likewise decreased to 1.54 percent in the Bollgard cotton to 4.99 percent in conventional cotton.
The percent of damaged bolls from stink bugs increased three-fold. Bollgard cotton had 2.96 percent damaged bolls from stink bugs compared with 1.04 percent for conventional cotton.
When comparing late-season insecticide sprays over the eight-year period, Bollgard cotton received 0.87 sprays compared with 2.63 sprays for conventional cotton.
Trends also suggest that stink bug damage is not showing a steady increase, but rather about the same percentage each year.
The total boll damage during the eight-year period for Bollgard cotton was 4.65 percent; for conventional, 6.54 percent.
Over the past two years, North Carolina growers have planted 71 percent of their acreage to Bollgard cotton.
Based on a 2002 study looking at beet armyworms in Edgecombe County, N.C., and comparing conventional, Bollgard and Bollgard II, Bacheler says it would appear that sprays for caterpillars in Bollgard II cotton will be very rare in North Carolina. “The potential for damage from bug pests will therefore increase.”