Submitted to: Society for Invertebrate Pathology Annual Meeting
Publication Type: Abstract only
Publication Acceptance Date: 4/4/2003
Publication Date: 7/1/2003
Citation: Abstract. 2003. 2003 Annua lMeeting of the Society fo Invertebrate Pathology, Burlington VT USA July 26-30,2003. p.51 Interpretive Summary: The work reported here summarizes the initial phases of selecting candidate fungi for the biological control of the sugarbeet root maggot, the single most important insect pest in that crop. The selection of candidates was based on the criteria of virulence, conidial production in bench-scale solid substrate fermentation, conidial shelf life, and fungal growth at ecologically relevant temperatures. Preliminary field efficacy data with one of these candidates is also presented.
Technical Abstract: Sugar beets (Beta vulgaris L.) are beset by one important insect pest, the sugarbeet root maggot (Tetanops myopaeformis), several lesser pests such as wireworms (Coleoptera: Elateridae), and a trio of significant diseases, (1) seedling diseases caused by Aphanomyces and Pythium, (2) Rhizoctonia Crown and Root Rot, and (3) Cercospora Leaf Spot. Although sugar beets are grown on 550,600 hectares in the U.S. (2002) they are considered a minor crop and farmers have only a narrow choice of chemical insecticides (terbufos, phorate, aldicarb, chlorpyrifos). Many of these chemicals are in jeopardy from resistance or regulatory action. The main fungicides are limited in number and face resistance development. These aspects create an ideal stage for a biologically based, integrated system. Our group is studying the deployment of insect pathogenic fungi to manage the sugarbeet root maggot and wireworm, along with three agents from Montana State University, Bacillus sp. LS201, Bacillus subtilis MSU127, and Bacillus mycoides BAC J, to manage the sugar beet pathogens. These microbial tools are being developed with a view to ultimately integrate them with resistant/tolerant beet hybrids, microbial control agents of sugarbeet cyst nematode, cultural practices, use of disease and pest predictive models, and induced systemic resistance to create an integrated, biologically based pest and disease management program for sugar beets. Phase 1 of the entomological component has been the selection of candidate fungi based on the criteria of virulence, conidial production in bench-scale solid substrate fermentation, conidial shelf life, and fungal growth at ecologically relevant temperatures. Of 90 B. bassiana isolates from sugarbeet fields, only two were efficacious against the larval dipteran in a soil-based bioassay reflecting practical field rates (2.5x105 ' 2.5x106 conidia/gram of a silty clay soil). In contrast, a M. anisopliae from Norwegian Delia antigua, an isolate from a U.S. soybean cyst nematode, and one from a Canadian Limonius sp. were highly effective. (No M. anisopliae was isolated from sugarbeet fields using both Galleria-baiting and a dodine-based selective agar.) Initial field work with one M. anisopliae isolate has indicated considerable sugarbeet root maggot control potential.