Production factors involved in the formulation of Erynia neoaphidis as alginate granules

Granular formulations of the aphid-pathogenic fungus Erynia neoaphidis were produced by entrapping mycelia In alginate polysaccharide polymers. Four S wiss isolates were compared for the numbers of conidia discharged from the surface of alginate granules in standardized laboratory assays and two were considered to be suitable for further development. Conidiation was achieve d from granules produced using nozzle diameters of 2.0. 1.0 and 0.5 mm from glass burettes or a novel vibrating tip apparatus. The mean diameters of d ried granules varied from 0.5 to 1.8 mm. The addition of sucrose, potato st arch or chitin in alginate solutions significantly improved the numbers of discharged conidia. With freshly produced granules, there was a 14.2-fold i ncrease in sporulation from 6.3 to 89.7 conidia mm(-2) using 2% (w/v) sucro se. Increases of 1.6- to 2.3-fold, from 11.0 to 17.7 and 25.2 conidia mm(-2 ), were observed wing 5% (w/v) starch or chitin respectively. The overnight drying of granules in a laminar flow hood and storage for 4 days at 4 degr ees C made differences in sporulation more obvious. There was a 15.5-fold d ifference in conidial numbers of 12.4 and 0.8 conidia mm(-2) from granules with and without sucrose respectively. For starch and chitin, there were 76 .0- and 46.5-fold increases from 0.4 to 30.4 and 18.6 conidia mm(-2) respec tively. Fresh or dried alginate granules containing 2% sucrose and 5% starc h gave 8.6-26.6% infection in laboratory bioassays with nymphs of pea aphid , Acyrthosiphon pisum, which were not significantly different when compared with infections of 6.7-22.9% using agar cultures or unsupplemented granule s. Further studies on desiccation and storage regimes are required in order to improve the short-term shelf-life off. neoaphidis alginate granules.