Effects of Temperature on the Life Table Parameters of Trichogramma zahiri (Hymenoptera: Trichogrammatidae), an Egg Parasitoid of Dicladispa armigera (Chrysomelidae: Coleoptera)

Abstract

The influence of different temperatures on biological parameters of native strains of Trichogramma zahiri Polaszek (Hymenoptera: Trichogrammatidae), an egg parasitoid of rice hispa, Dicladispa armigera (Olivier) (Chrysomelidae: Coleoptera), was evaluated in the laboratory on its host. The key biological parameters of the parasitoid T. zahiri in relation to temperature were investigated to find out its candidature as a potential biological control agent of rice hispa. The highest number of eggs parasitized by T. zahiri was 15.7 eggs per female at 26°C, which differed significantly from those at 18, 22, 30, and 34°C (P<0.05). Development duration and longevity of T. zahiri decreased as temperature increased. Fecundity differed significantly at all constant temperatures. Emergence rates decreased at both high (34°C) and low (<26°C) temperatures. Female-biased sex ratio ranged from 54 to 70% at all constant temperatures. The lower temperature threshold for T. zahiri was 6.2°C for males and 6.95°C for females. The upper threshold temperatures were 35.82 and 35.87°C for males and females, respectively. Net reproductive rate (R0) was highest at 26°C compared with other temperatures. Mean cohort generation time (tG) and population doubling time (tD) decreased as temperature increased from 18 to 30°C. The daily intrinsic rate of increase (rm) and finite rate of increase were positively correlated with temperatures ranging from 18 to 30°C and then decreased at 34°C. The relevance of our results is discussed in the context of climatic adaptation and biological control.