Germination of uredospores of Uromyces phaseoli (bean rust) was stimulated by linear, branched, saturated, and unsaturated methyl ketones, in the range of 6-9 carbons, and by cyclic unsaturated ketones, particularly /3-ionone, which was used as a standard for bioassay of activity. In contrast to uredospores of Puccinia graminis f. tritici (stem rust of wheat), spores of U. phaseoli were not stimulated by linear or cyclic aldehydes or alcohols. Spores of U. phaseoli were induced to germinate in pustule by /3-ionone at concentrations lower than 0.5 ppm when diseased plants were placed in dew chambers overnight. Spores floated on water and exposed to vapors of 10 fA of /3-ionone for 20 s germinated 95% at the end of the 4-h germination period, compared to 1% for controls. Uredospores of Puccinia graminis f. tritici and Puccinia coronata (crown rust of oats) responded similarly to vapors of nonanal.More than 60 compounds have been shown to stimulate the germination of uredospores of Puccinia graminis Pers. f. tritici Eriks. & E. Henn (stem rust of wheat). These chemicals that stimulate germination range in length from 5 to 12 carbon atoms, and include alcohols, aldehydes, ketones, amines, cyclic and noncyclic derivatives, and sulfur derivatives (French, 1961;French and Gallimore, 1971). Two stimulatory compounds, nonanal and 6methyl-5-hepten-2-one (methylheptenone), were first found in uredospores of P. graminis (French and Weintraub, 1957;Rines et al., 1974); nonanal was found also in spores of Uromyces phaseoli (Reben.) Wint., but did not stimulate their germination. Spores of U. phaseoli have not been analyzed for content of methylheptenone, but this compound stimulated their germination (French et al., 1975a).
Immature stages of the rodent bot fly, Cuterebra tenebrosa Coquillett, from central Washington are described and illustrated. Redescription of both sexes of the adult fly are also provided. Larval cuticular spines and posterior spiracular patterns are distinctive for second instars. Important characters of third instars include shape and number of points on cuticular spines and papillae arrangement. C. tenebrosa parasitizes bushy-tailed wood rats (Neotoma cinerea) and desert wood rats (N. lepida) in the western United States and western Canada.
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