COMPARISON OF THE EFFECT OF HYDROXAMIC ACIDS FROM WHEAT ON 5 SPECIES OF CEREAL APHIDS

Feeding behaviour of five species of cereal aphids in wheat seedlings differing in hydroxamic acid (Hx) levels, was monitored via electrical penetration graphs (EPG). Aphid species could be grouped as sensitive to the feeding deterrent effect of Hx in the seedlings (Rhopalosiphum padi, Schizaphis graminum, Sitobion avenae, and Metopolophium dirhodu m) or insensitive to them (Rhopalosiphum maidis). However, when feedin g behaviour was studied in artificial diets containing Hx, all species were equally sensitive to Hx. The behaviour of R. maidis was further compared with that of R. padi through detailed EPG analysis. It was fo und that the insensitivity of R. maidis to Hx in seedlings may be due to a feeding strategy avoiding contact with the compounds by decreasin g the number of cellular punctures in live tissues other than sieve el ements during its way to the phloem.