Effect of Cold Storage on Parasitism and Survival of Aphidius colemani and Meteorus pulchricornis

When Aphidius colemani mummies were stored at four different temperatures (6, 8, 10 and 12 ± 1°C), they could be stored at 8°C for 10 days with over 50% adult emergence. A number of mummies of Rhopalosiphum padi parasitized by A. colemani adults emerged from mummies after 8°C storage clearly reduced with increasing duration of storage and especially declined with storage longer than 13 days showing < 20% parasitism. However, there were no differences in aphid parasitisms by A. colemani on 3 to 10 days after storage. Over 3 day storage at 8°C was adversely affected on survival of A. colemani adults. Therefore, cold storage of A. colemani adults is considered as an unsuitable method for mass production of biological control agent. When 2-day-old Meteorus pulchricornis cocoons were stored at 6, 8 and 10 ± 1°C, it was possible to be stored up to 63 days at 8°C, showing the highest emergence. With increasing of cold storage duration at 8°C, parasitism on 2 and 3 larval instar of Spodoptera litura by stored M. pulchricornis significantly reduced. However, parasitic rate by M. pulchricornis stored for 2 weeks was similar to that by 1 week stored ones. Therefore, M. pulchricornis cocoons could be stored up to 2 weeks at 8°C for stockpiling before release.