Abstract
Abstract: The results obtained are summarized as follows: (1) the active compounds of aphid's odour stimulated the syrphid females to deposit significantly higher percentages of eggs. These chemical compounds could be isolated by the solvent n‐pentane. (2) Gas chromatography mass spectral analysis of n‐pentane fractions of aphid's odour revealed the presence of several active peaks of hydrocarbon compounds. The active peaks ranged from docosane (C22) to octacosane (C28). Also, GC‐mass spectral analysis of n‐pentane fractions of the aphid‐extract supernatant showed the same chain of hydrocarbon compounds which is present in the aphid odour. (3) Bioassay of the different cosane compounds showed that the different concentrations of tricosane, tetracosane, pentacosane and hexacosane have a kairomonal effect on the syrphid females and the second concentration of C23CII, C24CII, C25CII and C26CII stimulated the syrphid females to deposit a significantly higher percentage of eggs. While hexacosane (C26) was the most abundant hydrocarbon compound in aphid kairomone, tricosane (C23) was the most active hydrocarbon compound. (4) Bioassay of the different mixtures of cosane compounds showed that HCM1, HCM2, HCM3, HCM4, HCM5 and HCM6 have a kairomonal effect on the syrphid females. The highest percentage of eggs was laid under the effect of the fourth mixture (HCM4) which contains tricosane (C23), tetracosane (C24), pentacosane (C25), hexacosane (C26) and octacosane (C28). (5) The chain of non‐volatile hydrocarbon compounds of aphid‐kairomone is secreted along with the cornicle secretion which contains volatile compounds. This kairomone stimulate the oviposition of syrphid females when it is received mechanically by the antennae. (6) The present study showed the importance of the different mixtures of cosane compounds as aphid‐kairomone. The use of aphid‐kairomone could be promising in aphid biological control instead of the heavy use of insecticides.
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