Abstract
The current laboratory study was designed to evaluate the effect of abiotic and biotic factors such as temperature, light intensity, relative humidity and host age on biological and ecological characteristics of Aphelinus asychis (Walker) parasitizing Aphis gossypii (Glover). The traits studied were developmental duration, mortality, sex ratio, longevity, fecundity and host feeding. A. asychis can completely develop and reproduce at temperatures 18°C and 30°C, light intensities of 1000 and 7000 lux and relative humidities of 30% and 60%. Temperature had a significant effect on the developmental duration as well as on the percentage and longevity of females, while mortality from mummification to emergence, fecundity and host feeding were only slightly affected. Relative humidity only affected the developmental duration of A. asychis. Light intensity had mostly affected the biological and ecological traits of A. asychis. High light intensity resulted in a shorter developmental duration, higher incidence of females and longer life span of the female parasitoid. A high tolerance to climatic variations and life cycle well adapted to this aphid host are properties that make it likely that A. asychis could be used for the biological control of the cotton aphid in greenhouses.
Highlights
The cotton aphid, Aphis gossypii Glover (Sternorrhyncha: Aphididae), is a phytophagous cosmopolitan species widely distributed in tropical, subtropical and temperate regions
The results indicate that A. asychis can develop in A. gossypii and reach the adult stage at all the temperatures, light intensities and relative humidities used
The same significant differences were recorded in the total developmental duration from egg to adult emergence
Summary
The cotton aphid, Aphis gossypii Glover (Sternorrhyncha: Aphididae), is a phytophagous cosmopolitan species widely distributed in tropical, subtropical and temperate regions. It is a major pest of many cultivated plants such as Cucurbitaceae, Rutaceae and Malvaceae. In Europe, the cotton aphid is an important agricultural pest of cucumber and some other greenhouse crops (Van Schelt 1993). Despite numerous studies of aphidophagous insects, only a few of them are suitable for use as biological control agents in greenhouses on a large scale because they do not always match the reproductive and developmental rates of aphids (Van Steenis, 1995b). Temperature is an important abiotic factor and in the case of parasitoids, light intensity affects parasitization success. Several authors describe the effect of day length on Aphelinus species (Yu, 1992; Bernal et al, 2001; Tatsumi & Takada, 2005b, 2006), but the influence of light intensity is unknown
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