A discrete host-parasitoid model with development of pesticide resistance and IPM strategies

The development of pesticide resistance significantly affects the outcomes of pest control. A quantitative depiction of the effects of pesticide resistance development on integrated pest management (IPM) strategies and pest control outcomes is challenging. To address this problem, a discrete host-parasitoid model with pesticide resistance development and IPM strategies is proposed and analyzed. The threshold condition of pest eradication which reveals the relationship between the development of pest resistance and the rate of natural enemy releases is provided and analyzed, and the optimal rate for releasing natural enemies was obtained based on this threshold condition. Furthermore, in order to reduce adverse effects of the pesticide on natural enemies, the model has been extended to consider the spraying of pesticide and releases of natural enemies at different times. The effects of the dynamic complexity and different resistance development equations on the main results are also discussed

DISPERSAL OF <i>TOMICUS PINIPERDA</i> (COLEOPTERA: SCOLYTIDAE) FROM OPERATIONAL AND SIMULATED MILL YARDS

AbstractThe pine shoot beetle, Tomicus piniperda (L.), is an exotic pest that is regulated by federal quarantines in the United States and Canada. Mark–release–recapture experiments were performed with infested logs coated with fluorescent powder to determine if overwintering beetles in logs would leave a mill yard if infested logs were transported to sawmills in uninfested areas. Overwintering T. piniperda adults were marked with powder as they emerged in spring. Dispersal studies were conducted in four simulated mill yards and five operational sawmills to determine whether T. piniperda would colonize only the log pile in which they overwintered, fly to nearby log piles, or disperse beyond the mill yard. Each simulated mill yard was composed of 36 uninfested red pine logs, Pinus resinosa Ait. (Pinaceae), and 12 α-pinene-baited funnel traps set up to 100 m from a central release pile of six uninfested red pine and nine infested logs of Scotch pine, Pinus sylvestris L. At the five operational sawmills, baited funnel traps were set up to 400 m outside of each mill yard. Overall, 482 T. piniperda galleries were found on the experimental logs recovered from the four simulated mill yards combined. Tomicus piniperda adults dispersed and attacked the most distant logs at 100 m from the release point in the simulated mill yards. Likewise, adults were captured in baited funnel traps at distances up to 230 m in simulated mill yards and 250 m around operational sawmills. Although numbers of recaptured T. piniperda were generally low, in all cases some adults dispersed outside the mill yards despite the presence of abundant suitable breeding material. Therefore, logs containing overwintering adults pose a risk of spreading T. piniperda if not processed prior to initiation of spring flight.</jats:p

Modeling evolution of resistance by Maruca vitrata (Lepidoptera: Crambidae) to transgenic insecticidal cowpea in Africa

Wecreated a detailed model of the Maruca vitrata (F.) and cowpea [Vigna unguiculata (L.) Walp] system to study the possible evolution of resistance by the insect to transgenic insecticidal cowpea, which is under development. We focused on population dynamics and genetics in a region of west Africa. We simulated single-toxin and pyramided (two-toxin) cowpea and emphasized conservative, worst-case scenarios in our analysis. The results indicate that as long as a pyramided, transgenic cowpea can be developed, seed saving by farmers and reliance on natural refuge are not major problems for resistance management. Furthermore, it is possible that one or both toxins in the pyramid may not need to be high dose for evolution to be delayed signiÞcantly ( 20 yr or 80 generations for resistance to become a concern if transgenic cowpea is deployed in areas where M. vitrata is endemic). If efforts are made to deploy transgenic cowpea only into the regions where M. vitrata is not endemic, then there is little to no concern with resistance emerging in the M. vitrata population

Analyzing haplodiploid inheritance of insecticide resistance in whitefly biotypes

We developed new methods for analyzing inheritance of insecticide resistance in haplocliploid arthropods and applied them to elucidate resistance of the whitefly Bemisia tabaci (Gennadius) to an insect growth regulator, pyriproxyfen. Two invasive biotypes of this devastating crop pest, the B biotype in Arizona and the Q biotype in Israel, have evolved resistance to pyriproxyfen. Here, we incorporated data from laboratory bioassays and crossing procedures exploiting haplodiploidy into statistical and analytical models to estimate the number of loci affecting pyriproxyfen resistance in strains of both biotypes. In tests with models of one to ten loci, the best fit between expected and observed mortality occurred with a two-locus model for the B biotype strain (QC-02) and for one- and two-locus models for the Q biotype strain (Pyri-R). The estimated minimum number of loci affecting resistance was 1.6 for the B biotype strain and 1.0 for the Q biotype strain. The methods used here can be applied to insecticide resistance and other traits in haplocliploid arthropods.Peer reviewe