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Mortality of horn fly (Diptera: Muscidae) larvae in bovine dung supplemented with loline alkaloids from tall fescue
- Dougherty, C.T., Knapp, F.W., Bush, L.P., Maul, J.E., Van Willigen, J.
- Journal of medical entomology 1998 v.35 no.5 pp. 798-803
- endophytes, lethal dose, Festuca arundinacea, alkaloids, seeds, dose response, Epichloe coenophiala, cattle manure, plant extracts, toxic substances, Haematobia irritans, larvae, insect control, biological development, mortality
- Larvae of arthropod ectoparasites of livestock, such as the horn fly, Haematobia irritans (L.), may be exposed to acyl-loline alkaloids in dung of ruminant livestock ingesting herbage of the tall fescue (Festuca arundinacea Schreb.)-endophyte association [Neotyphodium coenophialum (Morgan-Jones & W. Gams) Glenn, Bacon & Hanlin comb. nov.]. Biological activity of alkaloid-supplemented bovine dung was assayed by growth, development, and survival of 1st instars of horn fly. An extract from tall fescue seed, containing N-formyl loline (NFL), N-acetyl loline (NAL), and loline (59:21:20 by mass, respectively) caused 100% mortality of horn fly larvae when dung was supplemented at greater than or equal to 100 microgram/g. Probit analysis of data corrected for natural mortality indicated a LD50 of 30 microgram/g (95% fidicial limits: 20-49 microgram/g). When horn fly larvae were introduced to dung supplemented with up to 50 micromolar of acyl-loline derivatives, mortality of larvae varied significantly between alkaloids (P< 0.0001). Probit analysis indicated that NFL [LD50: 34 micromolar (95% fidicial limits: 3-53 micromolar) was more toxic than NAL [LD50:46 micromolar(0-83 micromolar) ], and that loline hydrochloride was not toxic.