Cereal aphid species: their natural enemies and efficiency of Lysiphlebus testaceipes (Cresson, 1880) to control Rhopalosiphum maidis (Fitch, 1856)

Cereal grains both for human consumption and animal feed are an essential component of global food systems. However, during production they are often targeted by various pest insects, including aphids. A survey was carried out from 2017 to 2021 in six cereal production sites in Tunisia to evaluate aphid diversity and identify natural enemies on Triticum turgidum subsp. durum (durum wheat), Hordeum vulgare (barley), Avena sativa (oat) and Triticum secale (triticale). Six aphid species belonging to four genera were recorded: Diuraphis noxia, Rhopalosiphum maidis, R. padi, Schizaphis graminum, Sitobion avenae and Sitobion fragariae. Among these, S. avenae and R. padi emerged as the most prevalent species across the majority of sites, infesting durum wheat, barley and triticale. Sc. graminum, R. maidis and D. noxia were less frequent, while S. fragariae was exclusively found on oat plants. Common aphid predators observed included Coccinella algerica, Hippodamia variegata and C. undecimpunctata, as well as syrphid flies such as Episyrphus balteatus and Sphaerophoria rueppellii. Lysiphlebus testaceipes was the sole parasitoid species detected, emerging exclusively from R. padi and R. maidis mummies. Furthermore, the study on the efficacy of L. testaceipes against R. maidis indicated that parasitism levels increased with the number of introduced parasitoid pairs. Aphid and natural enemy diversity were also evaluated.