METHOD TO IMMOBILIZE THE APHID-PATHOGENIC FUNGUS ERYNIA-NEOAPHIDIS INAN ALGINATE MATRIX FOR BIOCONTROL

Erynia neoaphidis is an important fungal pathogen of aphid pests world wide. There have been few reported attempts to formulate this natural agent for use in biocontrol. In the current study, factors involved in the immobilization off. neoaphidis hyphae in an alginate matrix were investigated, Hyphae of two isolates cultured in liquid medium were 22 0 to 620 mu m in length and 7 to 19 mu m in diameter with a 74 to 83% cytoplasmic content. The optimal concentration of low-viscosity sodium alginate for production of conidia from entrapped hyphae was 1.5% (wt /vol), and 0.1 and 0.25 M calcium chloride were equally suitable for u se as the gelling solution. Alginate beads were rinsed with 10% sucros e after gelling. However, beads should not be left for longer than 40 min in 0.1M calcium chloride or 10% sucrose to prevent a 10% loss in c onidial production. A 40% (vol/vol) concentration of fungal biomass pr oduced significantly more conidia than either 20% or the standard conc entration of 10%. This effect persisted even after bends were dried ov ernight in a laminar flow hood and stored at 4 degrees C for 4 days. C onidia from freshly produced alginate beads caused 27 to 32% infection in Pea aphids as determined by standardized laboratory bioassays. Thi s finding was not significantly different from infections in aphids in oculated with fresh mycelial mats or plugs from Petri dish cultures. I n conclusion, algination appears to be a promising technique for utili zing E. neoaphidis in the biocontrol of aphid pests.