Application of Techniques for Quantification of Soil-Borne Entomophthoralean Resting Spores

Larval behavior in Lymantria dispar increases risk of fungal infection

“…We knew that E. maimaiga was present in this area because throughout the 1994 field season, 90.9% E. maimaiga infection occurred among L. dispar larvae. In April 1994, the top 2-3 cm of soil from a 10-cm radius around the bases of five trees averaged 1050 E. maimaiga resting spores g -1 of dry soil (Hajek and Wheeler 1994). The egg mass density at the beginning of the 1995 field season was 2412 L. dispar egg masses ha -1 .…”

A PCR-based tool for the cultivation-independent monitoring of Pandora neoaphidis

“…As most aphid species are holocyclic in cold temperate areas, like Switzerland (Keller and Suter, 1980;Blackman and Eastop, 2007), obligate aphid-pathogenic fungi such as P. neoaphidis may have to survive during winter in absence of larval or adult host stages, and/or to co-migrate with migratory alate aphids originating from other climatic zones (Feng et al, 2004(Feng et al, , 2007. Some aphid-pathogenic entomophthoralean fungi have been reported to produce resting spores (zygospores or azygospores) in order to survive hostile conditions such as winter (Humber, 1989;Hajek and Wheeler, 1994). However, except for loricoconidia (Nielsen et al, 2003), which are thick-walled conidia no such survival structures have been reported for P. neoaphidis.…”

Using bioassays to estimate abundance of Entomophaga maimaiga resting spores in soil

“…For this purpose, the bioassay methods developed are specifically applicable for the resting spore densities present during this study. At other locations, Hajek and Wheeler (1994) have documented much greater densities of resting spores in soil at bases of trees after epizootics, e.g., 1201-3895 resting spores/g dry soil. When gypsy moth larvae are infected with large doses of E. maimaiga, rapid death due to septicemia often occurs instead of normal fungal development (A.E.H., unpubl.…”

“…Resting spore density can be high initially in the soil surrounding tree trunks after epizootics (Hajek et al, 1998) but we know little about temporal and spatial variability of this persistent stage. Methods for absolute counts of resting spores extracted from soil have been developed (Hajek and Wheeler, 1994;Li et al, 1988) but these methods are time consuming and labor intensive. As an alternative, methods to estimate resting spore density have been developed using either volumes of soil or bioassays (Weseloh and Andreadis, 2002) but relationships between these estimates and absolute counts of resting spores have never been assessed.…”

“…Subsamples were dried, wet sieved, and spores were collected on a 20 lm sieve, followed by density gradient centrifugation using Percoll (Hajek and Wheeler, 1994). In 1999, one subsample was counted for each cardinal direction per plot and in 2000 and 2001, two subsamples were counted for each of the two cardinal directions sampled per plot.…”