Effect of Temperatures and Cold Storage on Performance of Tetrastichus brontispae (Hymenoptera: Eulophidae), a Parasitoid of Brontispa longissima (Coleptera: Chrysomelidae)

Laboratory studies were conducted to determine the effect of temperature and cold storage on the performance of Tetrastichus brontispae (Ferriere) (Hymenoptera: Eulophidae), one of the major endoparasitoids against coconut hispine beetle, Brontispa longissima (Gestro) (Coleptera: Chrysomelidae). The results revealed that T. brontispae could successfully parasitize host pupae under all seven tested temperatures, but no adult emergence was observed at 32°C. It was also revealed that temperatures between 24 and 26°C appeared to be the optimum temperatures for parasitism, as these temperatures resulted in the most parasitized pupae and a significantly higher emergence rate and progeny production. These measurements significantly declined at 20, 30, and 32°C. This study confirmed developmental periods of parasitoid progeny decreased as the temperature increased, and sex ratio of this female-biased parasitoid was not affected by rearing temperatures. More importantly, this study indicated that cold storage of parasitized pupae could extend up to 30 d at 10°C, and a longer storage period had a significant adverse effect on mean adult emergence and parasitism performance. Ten days might be the optimum cold-storage period at 10°C, as parasitism performance, emergence rate, and progeny production at this storage period were similar to the control of 26°C. Furthermore, the developmental period, emergence rate, and sex ratio of progeny that emerged from cold-stored parasitized pupae were not influenced by storage periods, whereas parasitism performance of progeny decreased as storage period increased. This study suggests that about 24-26°C would be the optimal temperature for mass production and release of T. brontispae for biological control of B. longissima. These results also provide novel findings that a period of 10 d at 10°C may be more suitable and acceptable for ideal cold storage of parasitized pupae of T. brontispae.