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

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 degrees C, which differed significantly from those at 18, 22, 30, and 34 degrees 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 degrees C) and low ( < 26 degrees 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 degrees C for males and 6.95 degrees C for females. The upper threshold temperatures were 35.82 and 35.87 degrees C for males and females, respectively. Net reproductive rate (R-0) was highest at 26 degrees C compared with other temperatures. Mean cohort generation time (t(G)) and population doubling time (t(D)) decreased as temperature increased from 18 to 30 degrees C. The daily intrinsic rate of increase (r(m)) and finite rate of increase (lambda) were positively correlated with temperatures ranging from 18 to 30 degrees C and then decreased at 34 degrees C. The relevance of our results is discussed in the context of climatic adaptation and biological control.