Temperature Effects on the Development and Reproduction of ThreeTrichogramma(Hymenoptera: Trichogrammatidae) Species Reared onTrichoplusia ni(Lepidoptera: Noctuidae) Eggs

Abstract

The cabbage looper, Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae) is a generalist species and an important pest of Brassicaceae worldwide. Egg parasitoids are a feasible alternative for the control of this species. We evaluated the suitability of T. ni eggs as hosts for three Trichogramma Westwood (Hymenoptera: Trichogrammatidae) species and their tolerance to survive and develop within a range of temperatures between 15 and 30°C under laboratory conditions. The species evaluated were Trichogramma pretiosum Riley, Trichogramma atopovirilia Oatman and Platner, and Trichogramma acacioi Brun, Moraes and Soares. Parasitism rate was affected by temperature, parasitoid species, and by the interaction between these two factors. Parasitoids developed and reproduced in the range of temperatures evaluated, but Trichog. acacioi failed to parasitize T. ni eggs at 30°C. The highest parasitism rates of Trichog. atopovirilia and Trichog. pretiosum occurred at 20 and 25°C and Trichog. acacioi at 25°C, with parasitism rate above 70% in the three species. Parasitoid emergence was not affected by temperature or species. The estimated thermal constant and lower temperature threshold were 134.6 DD and 10.6°C for Trichog. pretiosum and 130.1 DD and 11.2°C for Trichog. atopovirilia. The results demonstrated that Trichog. pretiosum and Trichog. atopovirilia are the most suitable species for the control of T. ni, as they can remain active throughout the year in subtropical regions.

Effects of temperature and superparasitism on quality and characteristics of thelytokous Wolbachia-infected Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) during mass rearing

“…Similar to most studies 54–56 , we also found Trichogramma offspring achieved maximum fitness at an intermediate temperature and their development rate increased with temperature. Though Trichogramma offspring gain maximum fitness at an an intermediate temperature with a relatively low growth rate, the slow growth-high mortality hypothesis (SG-HG) predicts that slower growing larvae suffer greater mortality due to prolonged exposure to natural enemies in field conditions 57,58 .…”

Demographic parameters of the indigenous egg parasitoids, Trichogramma spp., parasitizing the invasive tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

“…The present study assured a female-biased sex ratio in all the tested Trichogramma spp. and confirmed the earlier reports where a female skewed sex ratio was found in T. pretiosum and T. chilonis on different hosts (Bueno et al 2010 andKrechemer andFoerster 2015).…”

“…Adults' emergence from the parasitized host eggs was more than 80% in each case, which is not so far from the findings of Ballal et al (2016) who reported 91.01 to 97.5% adult emergence in T. pretiosum parasitizing T. absoluta. Immature developmental period appears not to show much variation (9-10.8 days) with the egg parasitoid or the host insect, when reared at 25°C (Bueno et al 2010;Perveen et al 2012 andKrechemer andFoerster 2015). Female longevity, however, varied with both the parasitoid and the host species.…”

Effects of temperature on development, reproduction and size ofTrichogramma achaeae: implications for biological control

“…To further explore whether developmental acclimation can potentially improve the performance of T. achaeae, we tested how different developmental acclimation temperatures affected the above parameters. We hypothesised that (1) increasing ambient temperature would result in reduced longevity, development time and wing size as well as in increased fecundity up to an optimal temperature; (2) 25 ° C would be optimal as reported for other Trichogramma species (Krechemer et al, 2015); and (3) parasitoids acclimated at their optimal temperature would achieve a higher performance (in terms of fecundity or similar) than parasitoids acclimated at other temperatures.…”