Hirsutella Rhossiliensis Research Articles

Influences of Certain Fungicides on Parasitism of the NematodeCriconemella xenoplaxby the FungusHirsutella rhossiliensis

Seven fungicides commonly used in South Carolina peach orchards were tested in the laboratory and greenhouse for their effects on Hirsutella rhossiliensis, a fungal parasite of Criconemella xenoplax. Benomyl at 1, 5, and 10 μg a.i./ml completely inhibited hyphal growth of the fungus. Chlorothalonil, dicloran, iprodione, and triforine significantly suppressed hyphal growth at 20 μg a.i./ml, but captan inhibited growth only at 40 μg a.i./ml. Sulfur had no effect at the concentrations studied. Conidial germination and germ tube elongation were more sensitive to benomyl than to iprodione or triforine (...)

Rates of Spore Transmission, Mortality, and Production for the Nematophagous FungusHirsutella rhossiliensis

Transmission of spores of Hirsutella rhossiliensis to juveniles of Heterodera schachtii (J2) was quantified in soil microcosms (17 cm 3 ) containing loamy sand (−60 mbar matric potential) or coarse sand (−20 mbar) at 20 C. Transmission measured as the probability (P) of a J2 acquiring at least one spore (as a function of numbers of spores × 10 3 per microcosm [S], was greater in loamy sand (P = [1.05S]/[S + 31]) than in coarse sand (P = −0.006 + 0.0016S). The value of P was constrained between 1 and 0. Difference to the effects of soil spore diameter on nematode motility and the probability of a nematode passing but not contacting a spore (...)

Role of the second-stage cuticle of entomogenous nematodes in preventing infection by nematophagous fungi

Third-stage infective juveniles (dauers) in the nematode genera Steinernema and Heterorhabditis are ensheathed in their second-stage (J2) cuticles. Retention of the J2 cuticle by various species and strains of Steinernema and Heterorhabditis was determined after the dauers moved through 5 cm of sand. In general, Heterorhabditis spp. (89–100%) retained their J2 cuticles whereas Steinernema spp. (100%) lost theirs. When dauers of Steinernema and Heterorhabditis spp. with and without J2 cuticles (cuticles removed with either 0.05% sodium hypochlorite or passage through sand) were exposed to conidia of endoparasitic fungi (either Hirsutella rhossiliensis or Drechmeria coniospora), those without a J2 cuticle and with conidia adhering to the J3 cuticle became infected by the fungi. Conidia of H. rhossiliensis and D. coniospora did not adhere to the J2 cuticle of Steinernema spp. In contrast, conidia of both fungi adhered to the J2 cuticle of Heterorhabditis spp. but <0.7% of the dauers were infected. These results suggest that Heterorhabditis spp. may be better biological control agents of insects than Steinernema spp. in soils where nematophagous fungi are significant mortality factors.