 
Left: Sporulating grasshopper cadavers.
Right: Epizootic of E. grylli in clear-winged grasshoppers.
Note cadavers congregated at tops of stems. M.Ramos (both)
Entomophaga grylli
Zygomycetes: Entomophthorales
With contributions by Mark Ramos, Plant Protection, USDA-ARS, 331
US Plant Soil Nutrition Laboratory, Cornell University.
E. grylli is a species complex that has two distinct pathotypes
in North America: Entomophaga macleodii and Entomophaga calopteni.
In addition, another complex member, E. praxibuli has been introduced
from Australia. They all attack grasshoppers which are major pests of
crops and rangeland in the Western United States and Canada. In 1986,
approximately 55 million acres of western rangeland were infested by
grasshoppers and the economic cost is estimated at over $400 million
per year. A Grasshopper Integrated Pest Management Program was initiated
in 1986-1992 by USDA-APHIS researching integrated approaches to managing
grasshoppers preferable to application of expensive insecticides over
vast areas of rangeland.
Appearance
Entomophaga grylli is easily identified in the field. Shortly
before death, infected grasshoppers crawl to the top of plants and die
with their heads pointing upward and their legs wrapped tightly around
the stalks where they may remain for several days.
Habitat
Rangeland and cropland, predominantly in the Western U.S. and Canada.
 
Pests Attacked (Host Range)
E. macleodii infects grasshoppers in the subfamily Oedipodinae,
including band-wing grasshoppers. E. calopteni infects grasshoppers
in the genus Melanoplus. E. praxibuli infects both Oedipodinae
and Melanoplus species in the United States.
Life Cycle
The members of this species complex can be separated principally by differences
in vegetative growth patterns, the formation or lack of primary conidia,
the size of and number of conidial nuclei, isozyme polymorphism profiles,
and host and geographic ranges.
E. calopteni is monocyclic forming only overwintering resting
spores allowing disease cycles to occur in subsequent years. E. macleodii
and E. praxibuli are polycyclic, characterized by forming asexual
conidia and overwintering resting spores. Under proper environmental conditions,
(high humidity and rainfall) large numbers of conidia are formed on individual
grasshopper cadavers and forcibly discharged, resulting in several additional
disease cycles per season and dramatic increases in infection levels.
Relative Effectiveness
Periodic and widespread epizootics of grasshoppers in North America have
been attributed to E. grylli. In Australia, E. praxibuli
has caused epizootics in grasshopper populations under fairly dry conditions,
a consideration in its introduction into the many arid rangeland areas
where grasshoppers are pests.
Presently, the E. grylli complex has limitations as a biological
control agent. It cannot be mass produced, and it is weather-dependent.
In addition, there are over 600 species of grasshopper in North America
and it is not feasible to test all of these for susceptibility. However,
the introduction of E. praxibuli was part of a project involving
the study of other biological control agents including viruses, parasitoids
and the fungal pathogen, Beauveria bassiana. In an integrated
approach, the E. grylli complex would seem to have a niche.
Commercial Availability
Entomophaga grylli is not commercially available.
Taken from:
Ramos, Mark (1993) The isolation, implementation and evaluation of
Entomophaga praxibuli as a potential biological control agent
of North American grasshoppers. A project report submitted to the faculty
of the Graduate School of Cornell University in partial fulfillment
for the degree of Master of Professional Studies (Agriculture).
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Weeden, C.R., A. M. Shelton, and M. P. Hoffman. Biological Control: A Guide to Natural Enemies in North America.
http://www.nysaes.cornell.edu/ent/biocontrol/ accessed (date).
Suggestions, corrections, and/or comments are appreciated: Contact
Tony Shelton (ams5@nysaes.cornell.edu).
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