Sporulation, storage and infectivity of obligate aphid pathogenPandora nouryigrown on novel granules of broomcorn millet and polymer gel

Abstract

Aims: Producing granular cultures of obligate aphid pathogen Pandora nouryi for improved sporulation and storage. Methods and Results: Small millet–gel granules were made of the mixtures of 80–95% millet powder with 5–20% polymer gel (polyacrylamide, polyacrylate or acrylate‐acrylamide copolymer) and inoculated with mycelia at 30 mg biomass g−1 dry granules plus 87·5% water, followed by static incubation at 20°C for 4–12 days. The fungus grew well on 12 preparations but best on that including 10% copolymer. An 8‐day culture of this preparation discharged maximally 58·5 × 104 conidia mg−1 granule at 100% RH and was capable of ejecting conidia at the nonsaturated regimes of 86–97% RH. During storage at 6°C, granular cultures with >85% water content had twofold longevity (120 days) and half‐decline period (34–36 days) of those stored at room temperature. The steadily high water content preserved the cultures better than that decreasing at 6°C. However, conidia from 70‐day‐stored granules were less infective to Myzus persicae nymphs than those from fresh ones based on their LC50s. Conclusions: The millet–gel granules had higher sporulation capacity than reported Pandora cultures and a capability of spore discharge at nonsaturated humidity. Significance and Impact of the Study: The granular cultures are more useful for aphid control.

Biotic and abiotic regulation of resting spore formation in vivo of obligate aphid pathogen Pandora nouryi: Modeling analysis and biological implication

“…It is no doubt that inoculum levels increase with the degree of fungal prevalence, which determines a density of mycosed cadavers in host cohorts. High spore concentrations, such as hundreds of conidia per square millimeter, can be achieved in some cohorts suffering from a mycosis, due to the large sporulation capacity of cadavers (Zhou and Feng, 2009;Hemmati et al, 2001), and also imply a forthcoming event that host individuals to be infected will be reduced by the developing epizootic. Host availability becomes minimal after epizootic outbreak.…”

“…This is because fresh cadavers killed by P. nouryi have a mean sporulation capacity of 4.2 Â 10 4 conidia per capita (Zhou and Feng, 2009). Primary conidia can be discharged 2-11 mm away from a cadaver (Hemmati et al, 2001), forming a spore halo of 13-95 mm 2 .…”

A floatable formulation and laboratory bioassay of Pandora delphacis (Entomophthoromycota: Entomophthorales) for the control of rice pest Nilaparvata lugens Stål (Hemiptera: Delphacidae)

“…However, it is difficult to develop a mycoinsecticide based on entomophthoralean fungi because the conidia are short lived and hard to harvest and spray . Several mycelium‐based entomophthoralean formulations, including mycelial mats, broomcorn pellets, alginate beads and humectant granules, have been manufactured, to take advantage of their superior sporulation characteristics . These formulations can sporulate upon exposure to damp air but cannot be used in paddy fields because their solid structures cause them to sink beneath the water and cease sporulation.…”