Environmental Entomology (1983) 12, 1350-1355

G.L. Nordin, G.C. Brown and J.A. Millstein (1983)
Epizootic phenology of Erynia disease of the alfalfa weevil, Hypera postica (Gyllenhal) (Coleoptera: Curculionidae), in central Kentucky
Environmental Entomology 12 (5), 1350-1355
Abstract: The phenology of Erynia epizootic development among larval alfalfa weevil, Hypera postica (Gyllenhal), populations in central Kentucky during 1979 through 1982 is described. Critical biological and physical factors governing initiation, progression, and termination of the epizootic under field conditions are identified. The first incidence of Erynia disease in H. postica in central Kentucky occurred between 200 and 290 celsius day-degrees accumulated from 1 January, using a base temperature of 9°C. Day-degrees were used to initiate annual field sampling but did not fully explain differences in overall epizootic phenology. Although the general sigmoid shape of Erynia epizootic mortality curves were very similar in 1979 through 1982, certain microclimatic factors appeared to dictate the magnitude and duration of the epizootics after first incidence of disease was observed. It is proposed that accumulated moisture above a base humidity threshold can serve as a key factor for explaining epizootic behavior as related to favorable and unfavorable conditions for conidial development and discharge. Natural termination of Erynia epizootics occurred when host densities fell below a critical threshold density value of 1.7 larvae per stem.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
population dynamics/epizootiology
environment/habitat manipulation

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Hypera postica	Alfalfa/lucerne (Medicago sativa)	U.S.A. (NE)
Zoophthora phytonomi (entomopathogen)	Hypera postica	Alfalfa/lucerne (Medicago sativa)	U.S.A. (NE)