, Volume 18, Issue 3, pp 305–315 | Cite as

Nosema whitei, a microsporidan pathogen of some species ofTribolium

IV. The effect of temperature, humidity and larval age on pathogenicity forT. castaneum
  • R. J. Milner
Mémoires Originaux


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.


Development Time Plant Pathology High Humidity Larval Instar Infected Larva 
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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'âge; 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.


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Copyright information

© Le François 1973

Authors and Affiliations

  • R. J. Milner
    • 1
  1. 1.Department of Agricultural ZoologyUniversity of Newcastle-upon-TyneEngland

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