1992 Annual Report for ANE92-015
Fungal Pathogens For BioControl of Sweetpotato Whitefly in Greenhouses
Summary
The sweetpotato whitefly, Bemisia tabaci (SPWF), is a major new pest of northern greenhouse crops. With a reported host range of over 400 plants and an ability to transmit over 60 plant viruses, this pest poses a serious threat to the greenhouse industry.
Control with conventional techniques is difficult because of the natural tolerance of SPWF egg and pupal stages to most chemical pesticides and the rapid development of insecticide resistance. Production and distribution of plants by large-scale propagators using intensive spray regimes significantly contributes to the development and spread of insecticide-resistant strains of SPWF.
New management approaches are needed. We have recovered a variety of entomogenous fungi from diverse source materials collected in Vermont. The pathogenicity of a number of these indigenous isolates to western flower thrips (WFT) has already been demonstrated. Our objectives are to conduct pathogenicity tests against SPWF using a range of WFT-active strains of Verticilium lecanii, Beauveria bassiana, Metarhizium anisopliae and Paecilomyces farinosus. Active strains will then be evaluated against different SPWF developmental stages. By using a broad base of strain types we will be able to identify the most active strains for use against SPWF.
Knowing the relative susceptibility of the different SPWF developmental stages to a selection of fungal pathogens, we will be able to establish which stage can most effectively be targeted with a fungal treatment, the spore dose required, and whether one fungal isolate could, potentially, be used to control all stages. By initially selecting strains that exhibit toxicity to WFT we will also be able to show which of the fungal isolates have the greatest promise for use against other pest species, making them a more cost-effective and attractive proposition for commercial greenhouse use.