Effectiveness of Lysiphlebus testaceïpes Cresson as biocontrol agent of Aphis gossypii Glover infesting pepper plants

In Tunisia, greenhouse crops are damaged by Aphis gossypii Glover and Myzus persicae Sulzer (Ben Halima Kamel 1991; Ben Halima Kamel and Ben Hamouda 1993, 1998). These aphids are considered to be the most dangerous pests of pepper because of their biology and biotic potential (Ben Halima Kamel 1991; Blackman and Eastop 2000). There are several ways of controlling these pests with chemical control being the most widely used. This method has more disadvantages than benefits (Gibson et al. 1982). The use of natural enemies to control aphids is an effective way of improving the yield and quality of protected crops. There are many studies on the following naturally occurring enemies of A. gossypii: Aphidius matricariae Haliday, Lysiphlebus fabarum Marshall, Aphidoletes aphidimyza (Rondani), Episyrphus balteatus (De Geer) (Ben Halima Kamel and Ben Hamouda 1998) and Lysiphlebus testaceipes (Cresson) (Ben Halima Kamel, unpublished data, 1999). It is now important to evaluate the effectiveness of L. testaceipes as a biocontrol agent of A. gossypii. This parasitoďd was introduced into the Mediterranean area (Carver and Franzmann 2001) and is thought to be an important parasite of A. gossypii (Lopes et al. 2007). The aim of this mainly laboratory study was to determine the factors affecting the establishment and success of a biological control agent, in particular the number of L. testaceďpes relative to the initial density of A. gossypii, needed to control the aphid. In addition, the effect of the L. testaceďpes on structure of A. gossypii populations was evaluated. Furthermore, the effectiveness of L. testaceipes in controlling A. gossypii infesting a protected crop of pepper plants and the subsequent effect on the growth of the pepper plants was also evaluated.