Sleeping beauties: Horizontal transmission by Entomophthoralean Fungi via resting spores

Authors: HAJEK, ANN - Cornell University; STEINKRAUS, DONALD - University Of Arkansas; Castrillo, Louela

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2018
Publication Date: 8/14/2018
Citation: Hajek, A.E., Steinkraus, D.C., Castrillo, L.A. 2018. Sleeping beauties: Horizontal transmission by Entomophthoralean Fungi via resting spores. Insects. 9(3). https://doi.org/10.3390/insects9030102.
DOI: https://doi.org/10.3390/insects9030102

Interpretive Summary: Most of the fungi in the order Entomophthorales are pathogenic to insects, and many have been investigated as possible biological control agents against insect pests of agriculture, forest, and health. These fungi can persist in the field for long periods of time via production of thick-walled resting spores. Factors determining their field persistence, germination, and host transmission are varied, including biotic, such as mycoparasites, and abiotic factors. Knowledge of these factors is critical in understanding the variables that contribute to the ability of these fungi to cause epizootics in the field, resulting in a dramatic decline of insect populations. This article is an overview of the latest information on entomophthoralean resting spore transmission, information critical in the utilization and development of these fungi as biological control agents.

Technical Abstract: Many of the almost 300 species of entomophthoralean fungi are known for being quite host specific and able to cause epizootics. Most species produce two types of spores, conidia and resting spores, and it is the resting spores that allow short and long term persistence, followed by horizontal transmission. Cadavers in which resting spores are produced are often found in different locations than cadavers of the same host producing conidia. Resting spores generally are dormant directly after production and require specific conditions for germination. Although experimental studies with resting spores are few, infections from E. maimaiga resting spores differ reproductively from conidial infections. Resting spores can germinate for either shorter periods or for several months, providing primary infections to initiate secondary cycling based on conidial infections, and not all resting spores germinate every year. Molecular methods have been developed to improve environmental quantification of resting spores, which can exist at high titers after epizootics. Community-based studies have demonstrated that this source of primary inoculum in the environment can decrease not only due to germination but also due to activity of mycopathogens.