Estratégias de armazenamento e aptidão de Palmistichus elaeisis (Hymenoptera: Eulophidae) em regime de temperatura flutuante visando sua criação massal

Abstract

One of the important points for the successful use of biological control agents is the improvement of storage techniques to optimize mass breeding, considering the quality of the biological input produced. In this research, we used endoparasitoid from Palmistichus elaeisis (Hymenoptera: Eulophidae) pupae to determine the best temperature/time relationship for storage of parasitized and non-parasitized pupae of the alternative host Tenebrio molitor (Coleoptera: Tenebrionidae) and females of the endoparasitoid. Cycle duration was evaluated; percentage of parasitism and emergence; number of offspring, sex ratio and longevity of males and females. In the three bioassays, the longevity of females was greater than that of males. All T. molitor pupae stored and, after being offered, P. elaeisis females were parasitized and there was no effect of temperature and storage time on sex ratio. Considering quality criteria such as emergence rate, progeny and longevity of P. elaeisis adults, it is possible to obtain a reasonable performance of the parasitoid by providing pupae stored at temperatures between 15 and 20 oC for a period of 10 to 15 days. Based on the same previous criteria, in addition to the sexual ratio, it was found that the supply of T. molitor pupae stored after 15 days of parasitism provided good performance of the parasitoid as long as the minimum temperature is around 15 oC and for a period maximum 13 days of storage. Finally, when storing P. elaeisis females for up to 6 days at 15oC, their reproductive performance was little affected. Also without detaching from quality control and aiming to produce a more vigorous biological input, we simulated different temperature conditions to measure the fitness of the P. elaeisis population maintained in a Fluctuating Thermal Regime (RTF) of 30 ± 2 °C during the day and 20 ± 2 °C at night, which was contrasted with the population maintained in a Constant Thermal Regime (RTC) of 25 ± 2 °C. The performance of the parasitoid, physical fitness and thermal tolerance of females were evaluated for seven generations. The P. elaeisis population maintained in RTF with a thermal oscillation of 10 oC day/night degenerated after the 5th generation and its performance was compromised over the generations. Regarding the physical conditioning of P. elaeisis females kept in RTF, it was found that accumulated fertility was 2.7 times lower than in RTC. Furthermore, females subjected to extreme temperatures of 30 and 35 oC survived for a short period with reduced rates of parasitism and absence of emergence, making it possible to only evaluate thermal tolerance for temperatures of 15 and 20 oC. In general, there was a greater effect on daily and accumulated fertility and daily and accumulated fertility in the population maintained in RTF in relation to RTC and between generations. Our results indicate that the use of RTF within the 10 oC range did not allow the production of P. elaeisis within an acceptable quality standard to be adopted in biofactories.