The influence of constant temperatures on biological parameters of German strains of Trichogramma aurosum Sugonjaev & Sorokina (Hymenoptera: Trichogrammatidae) was evaluated in the laboratory on eggs of Cydia pomonella L. (Lepidoptera: Tortricidae). Development time and longevity of all strains were decreased as temperature increased. Development time of the strains differed significantly only when exposed to 15A degrees, 20A degrees, and 25A degrees C. Cumulative fertility and longevity differed significantly at 15A degrees and 20A degrees C. Realized fertility differed significantly at all constant temperatures. Emergence rates of all strains were less than 65% and were decreased even further as temperature increased. Female-biased sex ratio ranged from 65% to 100% at all constant temperatures. The low temperature threshold for T. aurosum was 10A degrees C and the mean number of degree-days at 15A degrees, 20A degrees, 25A degrees and 30A degrees C was 175, 183, 173 and 185, respectively. The Bavarian strain tolerated high temperatures and had the highest parasitization capability, while the Hessian strain had the lowest parasitization at all temperatures. Fertility life table analysis revealed a major effect of temperature on the population growth parameters. Net reproductive rate was highest at intermediate constant temperatures in all strains, with the highest rate recorded for the Bavarian strains at all constant temperatures. Mean cohort generation time, and population doubling time decreased as temperature increased. The daily intrinsic rate of increase and finite rate of increase were positively correlated with temperature. The relevance of our results is discussed in the context of climatic adaptation, intraspecific variability and biological control.
Samara, R; Monje, JC; Zebitz, CPW; Qubbaj, T
Comparative biology and life tables of Trichogramma aurosum on Cydia pomonella at constant temperatures
Phytoparasitica