Nosema whitei,a microsporidan pathogen of some species ofTribolium |
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Authors: | R J Milner |
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Institution: | (1) Department of Agricultural Zoology, University of Newcastle-upon-Tyne, England;(2) Present address: Division of Entomology, C.S.I.R.O., 2350 Armidale, N.S.W., Australia |
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Abstract: | The pathogenicity ofNosema whitei was studied using a dose-mortality technique; larvae ofTribolium castaneum were reared for the duration of each experiment in flour mixed with known numbers of spores. The susceptibility of each of
the first 5 larval instars was compared. The LD50 (for mortality after 20 days) increased consistently from the first instar (1.8×106 spores/g) to the fifth instar (1.0×1010 spores/g). The slopes of the probit lines increased consistently as age increased (from b=1.1 to b=3.9). Two factors which
reduce the development time ofT. castaneum, high temperature and high humidity, both reduced the pathogenicity ofN. whitei. Thus pathogenicity decreased as the temperature was increased fram 25°C (LD50=4.2×106) through 30°C (LD50=1.3×107) to 35°C (LD50=3.2×106), also pathogenicity decreased consistently as humidity was increased fram 10%, through 30, 50, 70% to 90% R.H. Adults, emerging
fromNosema free larvae, became infected only when exposed to a very high dose (2×1010 spores/g for 14 days from the day of emergence). Infected larvae were treated for 1 hr. at 45°C in an attempt to cure the
infection. The infected larvae were not cured, rather the treatment had an adverse alfect on their survival.
Résumé La pathogénicité deNosema whitei a été étudiée en élevant des larves deT. castaneum dans de la farine mélangée à des quantités connues de spores. La sensibilité des larves diminue uniformément en fonction
de l'age; La DL50 varie de 1,8×106/g (1er stade) à 1,0×1010 spores/g (5e stade). Deux facteurs, qui accélèrent le développement deT. castaneum, des températures et des humidités élevées, réduisent tous les deux la pathogénicité deN. whitei.
Les adultes ne peuvent être infectés qu'en les exposant à la dose extrêmement élevée de 2×1010 spores/g.
Un traitement par la chaleur (45°C pendant une heure) n'a pas réussi à guérir les larves.
This work financed by a Science Research Council (U.K.) studentship is based on a thesis submitted for a degree of Ph. D.
at the University of Newcastle-upon-Tyne. |
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