Main content area

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.