|DUNKEL, FLORENCE - Montana State University
|SEDLAK, CHRISTOPHER - Montana State University
|MEILER, SVENJA - Montana State University
|LA VEAUX-VEO, KENDRA - Montana State University
Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/12/2010
Publication Date: 6/1/2010
Citation: Dunkel, F.V., Jaronski, S., Sedlak, C.W., Meiler, S.U., La Veaux-Veo, K.D. 2010. Effects of Steam-Distilled Shoot Extract of Mexican Marigold, Tagetes minuta (Asterales: Asterceae), and Entomopathogenic Fungi on Larval Tetanops myopaeformis (Roder). Environmental Entomology. 39(3): 979:988.
Interpretive Summary: Mexican marigold offers a multipurpose tool for managing plant pathogenic soil fungi, plant pathogenic soil nematodes, as well as other soil dwelling pests. Its tissues contain several insecticidal compounds that are potential or actual biorational pesticides in the U.S. Delivery methods can include direct soil incorporation of marigold biomass (green manure), alternative cropping with the plant, or use of marigold-derived oil as a botanical insecticide. Insect studies have been done primarily with: Lepidoptera such as fall armyworm, mosquitoes, and stored product Coleoptera, with potential against other Diptera, and other Coleoptera, such as wireworms. The fungus Metarhizium anisopliae is under development for use against a variety of soil insect pests, and several strains have been commercialized in the U.S. and elsewhere. There is potential for the two to be used concurrently. Our research was conducted to answer fundamental questions regarding the use of T. minuta as one component in pest management packages for organic cropping systems. In laboratory assays, we observed that Mexican marigold essential oil causes dose-dependent mortality and developmental arrest of the sugarbeet root maggot but does not interfere with the action of entomopathogenic fungi when the marigold extract and fungus are applied together.
Technical Abstract: Interactions of a formulation of steam distilled shoot extract of Mexican marigold, Tagetes minuta, and entomopathogenic fungi were evaluated for management of the sugarbeet root maggot, Tetanops myopaeformis (Röder). Shoot extract plus surfactant was used to test the hypothesis that this fungicidal, and nematocidal biopesticide causes dose-dependent mortality and developmental arrest of T. myopaeformis, but does not interfere with the action of entomopathogenic fungi when applied together. A soil-Petri dish bioassay system was developed to test the hypothesis. For diapausing, non-feeding but active 12-month-old third-instar larvae, 0.5% A.I. T. minuta shoot extract was sufficient to prevent pupation without mortality, but 0.75% A.I. was lethal for 93 percent of the test insects. The effect of T. minuta shoot extract on fungal efficacy under simultaneous use was investigated using a model system of two entomopathogenic fungi, Beauveria bassiana (Bals.) Vuillemin. TM28 and Metarhizium anisopliae var. anisopliae (Metsch.) Sorokin MA 1200, in a soil-based bioassay with larval sugarbeet root maggots. No adverse effects of T. minuta oil on action of entomopathogenic fungi and no synergy were found, only an additive effect of the T. minuta extract and each fungal isolate separately.