Comparison of Western Corn Rootworm (Coleoptera: Chrysomelidae) Adult Populations and Economic Thresholds in First-Year and Continuous Corn Fields1

Modeling Evolution of <I>Diabrotica virgifera virgifera</I> (Coleoptera: Chrysomelidae) to Transgenic Corn With Two Insecticidal Traits

“…Coats et al (1987) observed no unmated females ßying before the third day after emergence. In a study of dispersal from continuous to Þrst-year cornÞelds in a region, Godfrey and Turpin (1983) observed Ϸ70 Ð 80% of females in Þrst-year corn by the end of each generation. Because Godfrey and Turpin (1983) observed 3Ð 4 times as many females as males moving into Þrst-year cornÞelds from continuous corn Þelds, we assume that 25% of males disperse outside their natal Þeld.…”

“…In a study of dispersal from continuous to Þrst-year cornÞelds in a region, Godfrey and Turpin (1983) observed Ϸ70 Ð 80% of females in Þrst-year corn by the end of each generation. Because Godfrey and Turpin (1983) observed 3Ð 4 times as many females as males moving into Þrst-year cornÞelds from continuous corn Þelds, we assume that 25% of males disperse outside their natal Þeld. Thus, the proportion of males in a given genotype for each patch, is inßu-enced by PM, the proportion of males that disperse out of the natal cornÞeld before mating the Þrst or multiple times.…”

Influence of Corn Phenology on Adult Western Corn Rootworm (Coleoptera: Chrysomelidae) Distribution

“…Western corn rootworm beetles are very mobile insects with both trivial movement (Naranjo 1991(Naranjo , 1994 and migration (Coats et al 1986, Grant and Seevers 1989, Naranjo 1990) events impacting spatial dynamics over time. When movement occurs among cornÞelds (Hill and Mayo 1980), the majority of the dispersal activity appears to be by females (Hill and Mayo 1974, Godfrey and Turpin 1983, Naranjo 1991.…”

Abundance and Distribution of Western and Northern Corn Rootworm (<I>Diabrotica</I> spp.) and Prevalence of Rotation Resistance in Eastern Iowa

“…Both D. barberi and D. v. virgifera have evolved resistance to this management practice (Krysan et al 1984, reducing the beneÞts of crop rotation in some areas. In addition to crop rotation, farmers can scout cornÞelds for adults to determine whether management of larval D. barberi and D. v. virgifera will be necessary the following season (Godfrey andTurpin 1983, Hein andTollefson 1985). In this 2-yr study we measured the abundance of D. barberi and D. v. virgifera, the prevalence of rotation resistance in these species, and then mapped these measurements using ArcGIS.…”

“…focus on the adult population size to predict the severity of larval injury to corn the following year. One method uses whole-plant counts, with counts Ͼ1.62 and 0.71 adults per plant for continuous cornÞelds and Þrst-year cornÞelds, respectively, predicted to cause economic damage (Godfrey and Turpin 1983). Another method uses sticky traps deployed throughout a Þeld to estimate adult abundance.…”