Applying an integrated refuge to manage western corn rootworm (Coleoptera: Chrysomelidae): effects on survival, fitness, and selection pressure.
The refuge strategy can delay resistance of insect pests to transgenic maize producing toxins from Bacillus thuringiensis (Bt). This is important for the western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), because of its history of adaptation to several management practices. A 2-yr study across four locations was conducted to measure the effects of integrated refuge (i.e., blended refuge) on western corn rootworm survival to adulthood, fitness characteristics, and susceptibility to Bt maize in the subsequent generation. The treatments tested in this study were as follows: a pure stand of Bt maize (event DAS-59122-7, which produces Bt toxins Cry34Ab1/Cry35Ab1), a pure stand of refuge (non-Bt maize), and two variations on an integrated refuge consisting of 94.4% Bt maize and 5.6% non-Bt maize. Within the two integrated refuge treatments, refuge seeds received a neonicotinoid insecticidal seed treatment of either 1.25 mg clothianidin per kernel or 0.25 mg thiamethoxam per kernel. Insects in the pure stand refuge treatment had greater survival to adulthood and earlier emergence than in all other treatments. Although fecundity, longevity, and head capsule width were reduced in treatments containing Bt maize for some site by year combinations, Bt maize did not have a significant effect on these factors when testing data across all sites and years. We found no differences in susceptibility of larval progeny to Bt maize in bioassays using progeny of adults collected from the four treatments.
Department of Entomology, Iowa State University, 13 Insectary, Ames, IA 50011, USA. jennifer.maxwell@wartburg.edu
Jennifer L
JL
Petzold-Maxwell
Analiza P
AP
Alves
Ronald E
RE
Estes
Michael E
ME
Gray
Lance J
LJ
Meinke
Elson J
EJ
Shields
Stephen D
SD
Thompson
Nicholas A
NA
Tinsley
Aaron J
AJ
Gassmann
D000818:Animals; D001413:Bacillus thuringiensis / Q000235:genetics*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001517:Coleoptera / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D004731:Endotoxins / Q000235:genetics* / Q000378:metabolism; D005260:Female; D056084:Genetic Fitness; D006460:Hemolysin Proteins / Q000235:genetics* / Q000378:metabolism; D007305:Insecticide Resistance; D007814:Larva / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D008136:Longevity; D008297:Male; D015146:Midwestern United States; D009518:New York; D010572:Pest Control, Biological / Q000379:methods*; D030821:Plants, Genetically Modified / Q000235:genetics; D012641:Selection, Genetic; D003313:Zea mays / Q000235:genetics*
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis