Location: Emerging Pests and Pathogens ResearchTitle: First report of chytrid mycoparasitism of entomophthoralean azygospores Author
Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2013
Publication Date: 10/15/2013
Citation: Hajek, A.E., Longcore, J.E., Simmons, D.R., Peters, K., Humber, R.A. 2013. First report of chytrid mycoparasitism of entomophthoralean azygospores. Journal of Invertebrate Pathology. 114:333-336. Interpretive Summary: This paper describes basic information about a watermold fungus parasitizing another fungus, Entomophaga maimaiga, which is an important natural biocontrol agent of the gypsy moth. The long-lived resting spores of E. maimaiga are key to this biocontrol agent's effectiveness, and this is the first report of any other fungus having a negative impact on the numbers and survival of the resting spores. This paper describes the discovery and identification of the watermold parasite, and illustrates its development. We also provide information about the negative impacts of the watermold on the resting spores in forest soils. The discovery and documentation of this parasite raises a warning flag regarding the continued success of using E. maimaiga as a biocontrol agent for gypsy moth. This is also the first report of any fungus parasitizing any other fungus belonging to the large and important group of insect-pathogenic fungi that includes E. maimaiga and other major natural biocontrol agents.
Technical Abstract: Mycoparasitism–when one fungus parasitizes another–has been reported to affect Beauveria bassiana and mycorrhizal fungi in the field. However, mycoparasitism of any fungi in the Order Entomophthorales has never been reported before now. The majority of entomophthoralean species persist as resting spores (either zygospores or azygospores) in the environment and dormant entomophthoralean resting spores (whether formed as zygospores or azygospores) are thought to be especially well adapted for survival over long periods due to their thick double walls. Entomophthoralean resting spores can accumulate in the soil as large reservoirs of inoculum which can facilitate the onset and development of epizootics. We report parasitism of azygospores of the gypsy moth pathogen Entomophaga maimaiga caged in soil from southern Ohio by the chytrid fungus Gaertneriomyces semiglobifer. G. semiglobifer had previously been isolated from soil samples from North America, Europe and Australia or horse manure from Virginia. After isolation and identification of G. semiglobifer, azygospores of E. maimaiga exposed to zoospores of G. semiglobifer exhibited high levels of mycoparasitism and G. semiglobifer was subsequently reisolated from mycoparasitized resting spores. We discuss the importance of this finding to the epizootiology of insect diseases caused by entomophthoralean fungi