The effect of different oviposition and preadult development temperatures on the biological characteristics of four Trichogramma spp. parasitoids (Hymenoptera: Trichogrammatidae) species

Trichogramma parasitoids are effective biocontrol agents and a reliable component of integrated strategies against lepidopterous pests. The success of these parasitoids in pest management relies not only on their ability to parasitize their hosts but also on their adaptation to the climatic conditions of the release area, particularly temperature. The expression of life history traits of Trichogramma spp. can vary significantly with temperature, depending on the species or strains being tested. Trichogramma cacoeciae (Marchal), T. euproctidis (Girault), T. minutum (Riley), and T. brassicae (Bezdenko) (Hymenoptera: Trichogrammatidae) are currently used in biocontrol programs against important lepidopteran pests. We aimed to assess the temperature sensitivity of these parasitoids during oviposition and preadult development, and to identify the most tolerant species to high temperatures conditions commonly encountered in Mediterranean Basin countries during the growing seasons. The biological characteristics of the four species were determined at seven temperature regimes expressed as temperatures during oviposition and preadult development (25/25, 25/30, 25/35, 25/40, 30/30, 35/35 and 40/40 °C), using Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs. Trichogramma cacoeciae showed the highest level of parasitism at 30/30 °C, while the other species exhibited the highest levels at 25/25 °C and 25/30 °C. All Trichogramma species were able to develop and survive from 25 °C to 35 °C, but not at 40 °C. Temperature significantly affected the longevity and fecundity of female progeny, with both decreasing when the temperature increased from 25 °C to 35 °C. When exposed to 35/35 °C, T. cacoeciae demonstrated the most optimal performance in terms of parasitization efficiency, developmental capacity, progeny longevity, and fecundity.