For biological control it is necessary to store mass-reared biological control agents when the demand is low. The objective of this study is to increase their shelf life without significantly reducing their fitness. The ladybird Hippodamia variegata is a widespread and voracious aphidophagous predator, with an important role in decreasing the abundance of pest aphids in many parts of the world. We investigated the effect of storage at three temperatures: constant 1°C, constant 6°C, and an alternating thermal regime of 12°C/0°C (the higher temperature for 12 h and the lower one for another 12 h). They were exposed to each of the temperature regimes for either 15, 25, 35, 45 or 60 days. We recorded survival, pre-oviposition period, fecundity and voracity of adult H. variegata following storage. The survival of adult beetles significantly declined with increasing storage duration at all three temperatures. Storage at 6°C up to 35 days and at 12°C/0°C up to 45 days had no significant effects on the fecundity of the ladybirds, but storage for longer significantly decreased fecundity. Beetles stored at 1°C for any of the durations had significantly lower fecundities. Prolonged cold storage caused an increase in the pre-oviposition period at all storage temperatures. Generally, 6°C and 12°C/0°C are the best temperatures for storing the ladybirds as they had the least negative effect on their fitness. The results of this research can help in improving the quality of H. variegata stored for use as biological control agents in the following season.
The cucumber moth, Diaphania indica (Saunders) (Lepidoptera: Pyralidae), is a major pest of cucurbitaceous plants. The oviposition preference and olfactory response of larvae, mated and unmated male and female adults to volatiles emanating from uninfested and infested plants of four species of cucurbitaceous host plants and odours of conspecifics were recorded. Also the role of experience in the host finding behaviour of D. indica was evaluated. The experiments were done using a wind tunnel, olfactometer attraction assays and oviposition bioassays. The results reveal that fewer eggs were laid on infested plants than on uninfested plants. Females significantly preferred cucumber over squash, melon and watermelon. Cucurbitaceous plants elicited adults of D. indica to fly upwind followed by landing on the plants. The effect of experience on the olfactory preference of D. indica was dependent on the host plant. Females that had experience of cucumber, squash and melon plants were significantly attracted to the same plant, but not in the case of watermelon. Larvae of this pest were attracted only to volatiles of uninfested cucumber, squash and melon, whereas volatiles of conspecifics, infested plants and intact watermelon did not attract larvae. This study is an initial attempt to investigate the role of volatile infochemicals in the host-finding behaviour of D. indica. These results provide baseline information for the development of new control strategies against D. indica.