Encarsia sophia (Girault & Dodd) (Hymenoptera: Aphelinidae) is an important bio-control agent of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). Storage at low temperature is a valuable method used in the mass rearing of biological control agents to ensure the availability of sufficient parasitoids when needed. However, storing parasitoids at a low temperature may lead to a decrease in their fitness. The aim of this study was to determine the effect of different durations of constant low temperature storage on the fitness traits of the above parasitoid. The effect of storage at three temperatures (4, 8 and 12 ± 1°C, RH = 65-75% and in darkness) for periods of 1, 2 or 3 weeks and at two pupal stages (10 and 12 days old) was studied. The percentage emergence, time to emergence, longevity, size and ability of the females that emerged to parasitize B. tabaci were evaluated. The results indicate that there is a decrease in percentage emergence, longevity and ability to parasitize the longer and lower the temperature at which the pupae of E. sophia are stored. The percentage emergence of both pupal stages kept at 12°C for a week was not affected. However, at lower temperatures (8 and 4°C) percentage emergence after storage of two weeks decreased to 67-87.5% and after three weeks none emerged. The time to adult emergence was longer for 12 day old pupae at all temperatures and storage times. The longevity of the adults that emerged from both pupal stages after one week of storage at 12 and 8°C was not affected, but decreased to 66-72% with increase in storage time. There was no effect of cold storage on adult size when 10 day old pupae were stored. The ability of this parasitoid to parasitize B. tabaci after emerging from both pupal stages stored at all of the temperatures regardless of storage time was significantly lower. Effect of storage at 12°C for a week in terms of percentage emergence and longevity did not differ from that of the control, but nevertheless they were less able to parasitize B. tabaci. Although the information on the effect of cold storage on E. sophia is very limited, the results of this study indicate that for more efficient biological control there is an urgent need to improve the method of storing pupae.

This study was conducted to determine the insecticidal activity of essential oil from orange peel Citrus sinensis L. against maize weevil. The essential oil of fresh orange peel was obtained by hydrodistillation using a clevenger type apparatus. The study was conducted under laboratory condition. Different doses of essential oil of Citrus sinesis were tested. The experiments were arranged in a completely randomized design. Essential oil at the highest rate of 750 mg applied at 3 ml per filter paper gave 100 % mortality after 24 hours. In fumigation toxicity bioassay, 0.3 g of essential oil applied at the rate of 3 ml caused 61 % mortality within 24 hours. The treatment, however, showed lower repellency effect against maize weevil S. zeamais with 36 % repellency. The present study indicates that the orange oil has potential insecticidal characteristics, so it can be used as natural insecticides for storage pests.