ABSTRACT

In a 7-year, large-scale evaluation of pest shifts resulting from the adoption of Bt (Bollgard) cotton by North Carolina's cotton producers (Figure 1), 574 pairs of Bollgard and conventional cotton fields were assessed from 1996 through 2002 for mid- to late- season boll damage. Bollworm damage to bolls (Fig. 2) averaged 4-fold higher in conventionally protected cotton vs. Bollgard cotton (4.8% vs. 1.2%), while stink bug damage to bolls (Fig. 3) averaged just over 3-fold higher in Bollgard cotton (3.1% vs. 1.0%). Overall boll damage during this period favored Bollgard cotton by 1.6% (4.7% vs. 6.3%). European corn borer and fall armyworm damage to bolls was very light from 1996 to 2002. Bollgard cotton was treated an average of 2 times less per year (2.6 vs. 0.8) than conventional cotton. When considering many of the factors which affect insect control costs, such as the technology fee for Bollgard cotton seed, late-season insect control costs, the penalty of boll damage, and recommended relative scouting costs, the overall economic returns of Bollgard cotton, averaged over 1996 to 2002, were approximately $6.00 higher than of conventionally-protected cotton.