Influence of temperature and duration of leaf wetness on infection of Acyrthosiphon kondoi with Erynia neoaphidis

Abstract

S U M M A R YBioassays were carried out to examine the influence of temperature and duration of leaf wetness on the infectivity of an isolate of Erynia neoaphidis for its aphid host Acyrthosiphon kondoi. Preliminary experiments demonstrated that primary spores produced in vitro were as infectious as those formed in vivo. No consistent effect of temperature on infectivity of primary spores could be detected. The time taken to kill an aphid increased as temperature decreased, from 3-5 days at 20 OC to 12-15 days at 8 "C, suggesting a threshold for disease development of 4 OC. Increasing duration of the period of leaf wetness up to 24 h after inoculation increased the final level of infection. At 20 OC, a minimum moisture period of 3 h was required for infection with maximum infection occurring after about 7 h. These times increased slightly at 15 OC but extending to 7 and 16 h respectively at 10 OC. The epizootiological implications of these results are discussed with reference to previously published data on in vivo production of primary spores of E. neoaphidis.

Effect of temperature, humidity and photoperiod on mortality of Mononychellus tanajoa (Acari: Tetranychidae) infected by Neozygites cf. floridana (Zygomycetes: Entomophthorales)

“…Further, Tillotson et al (Carrier, 1976). Among arthropod hosts, the rate of mortality caused by fungal diseases increases with increasing temperature (Stimmann, 1968;Wilding, 1970;Milner and Bourne, 1983;Milner and Lutton, 1983;Eilenberg, 1987). However, this rate may decline once an optimum temperature is attained.…”

Plant waxy bloom on peas affects infection of pea aphids by Pandora neoaphidis

“…The number of cadavers on each plant was counted in the morning, 7 d after conidial exposure (156 h). Aphids succumbing to entomopathogenic fungi usually die in the late afternoon and evening (Milner and Bourne, 1983), and it takes a minimum of 72 h (Brobyn and Wilding, 1977;Butt et al, 1990) and generally 96 h (personal observations) following conidial exposure for A. pisum to die, so this interval was chosen to measure the maximum infection rate resulting from the initial exposure to conidia, and prior to the development of secondary infections from conidia having contacted the plant surface.…”

Winter prevalence of obligate aphid pathogen Pandora neoaphidis mycosis in the host Myzus persicae populations in southern China: modeling description and biocontrol implication

“…High (> 30°C) or low (< 4°C) temperatures inactivate most Entomophthorales, and in between, temperature significantly influences the span of infection cycle period, e.g., P. neoaphidis-killed aphids appear in 4.2, 6.9 and 13.6 days after maintained under fluctuating summer, autumn and winter temperatures in UK respectively (1,12). Light regime probably contributes to death of mycosed hosts occurring in late afternoon for mycosis diffusion on humid nights (12), and ultraviolet radiation otherwise shortens fungal survival duration (6).…”

“…High (> 30°C) or low (< 4°C) temperatures inactivate most Entomophthorales, and in between, temperature significantly influences the span of infection cycle period, e.g., P. neoaphidis-killed aphids appear in 4.2, 6.9 and 13.6 days after maintained under fluctuating summer, autumn and winter temperatures in UK respectively (1,12). Light regime probably contributes to death of mycosed hosts occurring in late afternoon for mycosis diffusion on humid nights (12), and ultraviolet radiation otherwise shortens fungal survival duration (6). Besides, host-related factors such as host density and other biotic factors including fungal infection level and actions of contaminated predators affect mycosis transmission, due to the efficiency of transmission dependent on contact probability of infectious conidia and healthy hosts (18,20).…”

“…RH) lasting several days, due to fungal sporulation, conidial germination and infection requiring near-saturated air humidity (12,22). High (> 30°C) or low (< 4°C) temperatures inactivate most Entomophthorales, and in between, temperature significantly influences the span of infection cycle period, e.g., P. neoaphidis-killed aphids appear in 4.2, 6.9 and 13.6 days after maintained under fluctuating summer, autumn and winter temperatures in UK respectively (1,12).…”