Large-Scale Evaluation of Association Between Pheromone Trap Captures and Cotton Boll Infestation for Pink Bollworm (Lepidoptera: Gelechiidae)

Derivation of Pheromone-Based Larval Thresholds in Spruce Budworm Accounting for Distance to Defoliated Forest Stands

Spruce budworm, Choristoneura fumiferana Clem. (Lepidoptera: Tortricidae), is the most severe defoliator of Pinaceae in Nearctic boreal forests. Three tools widely used to guide large-scale management decisions (year-to-year defoliation maps; density of overwintering second instars [L2]; number of males at pheromone traps) were integrated to derive pheromone-based thresholds corresponding to specific intergenerational transitions in larval densities (L2i → L2i+1), taking into account the novel finding that threshold estimates decline with distance to defoliated forest stands (DIST). Estimates of thresholds were highly variable between years, both numerically and in terms of interactive effects of L2i and DIST, which limit their heuristic value. In the context of early intervention strategy (L2i+1 > 6.5 individuals per branch), however, thresholds fluctuated within relatively narrow intervals across wide ranges of L2i and DIST, and values of 40-200 males per trap may thus be used as general guideline.

Transgenic cotton and sterile insect releases synergize eradication of pink bollworm a century after it invaded the United States

Invasive organisms pose a global threat and are exceptionally difficult to eradicate after they become abundant in their new habitats. We report a successful multitactic strategy for combating the pink bollworm (Pectinophora gossypiella), one of the world's most invasive pests. A coordinated program in the southwestern United States and northern Mexico included releases of billions of sterile pink bollworm moths from airplanes and planting of cotton engineered to produce insecticidal proteins from the bacterium Bacillus thuringiensis (Bt). An analysis of computer simulations and 21 y of field data from Arizona demonstrate that the transgenic Bt cotton and sterile insect releases interacted synergistically to reduce the pest's population size. In Arizona, the program started in 2006 and decreased the pest's estimated statewide population size from over 2 billion in 2005 to zero in 2013. Complementary regional efforts eradicated this pest throughout the cotton-growing areas of the continental United States and northern Mexico a century after it had invaded both countries. The removal of this pest saved farmers in the United States $192 million from 2014 to 2019. It also eliminated the environmental and safety hazards associated with insecticide sprays that had previously targeted the pink bollworm and facilitated an 82% reduction in insecticides used against all cotton pests in Arizona. The economic and social benefits achieved demonstrate the advantages of using agricultural biotechnology in concert with classical pest control tactics.

Global Patterns of Resistance to Bt Crops Highlighting Pink Bollworm in the United States, China, and India

Crops genetically engineered to produce insecticidal proteins from Bacillus thuringiensis (Bt) have advanced pest control, but their benefits have been reduced by evolution of resistance in pests. The global monitoring data reviewed here reveal 19 cases of practical resistance to Bt crops, which is field-evolved resistance that reduces Bt crop efficacy and has practical consequences for pest control. Each case represents the responses of one pest species in one country to one Bt toxin. The results with pink bollworm (Pectinophora gossypiella) and Bt cotton differ strikingly among the world's three leading cotton-producing nations. In the southwestern United States, farmers delayed resistance by planting non-Bt cotton refuges from 1996 to 2005, then cooperated in a program that used Bt cotton, mass releases of sterile moths, and other tactics to eradicate this pest from the region. In China, farmers reversed low levels of pink bollworm resistance to Bt cotton by planting second-generation hybrid seeds from crosses between Bt and non-Bt cotton. This approach yields a refuge of 25% non-Bt cotton plants randomly interspersed within fields of Bt cotton. Farmers adopted this tactic voluntarily and unknowingly, not to manage resistance, but apparently because of its perceived short-term agronomic and economic benefits. In India, where non-Bt cotton refuges have been scarce and pink bollworm resistance to pyramided Bt cotton producing Cry1Ac and Cry2Ab toxins is widespread, integrated pest management emphasizing shortening of the cotton season, destruction of crop residues, and other tactics is now essential.