Influence of cereal leaf epicuticular wax on Diuraphis noxia probing behavior and nymphoposition

The effect of cereal leaf surface wax on Diuraphis nox-ia (Mordvilko), the Russian wheat aphid, probing behavior epicuticular wax from wheat (Triticum aestivum L.) c.v. 'Arapahoe' and 'Halt' was different from barley (Hordeum vulgare L.) c.v. 'Morex', and oat (Avena sativa L.) c.v. 'Border'. Both wh eat cultivars had similar rod-shaped epicuticular wax, while barley and oat plants had flakes;es. The chemical composition comparison of gas chromatog rams also indicated that the extract of the two wheat cultivars had similar pattern of peaks. while the barley and oat leaves had similar peaks. Cerea l variety significantly affected aphid probing behavior (P < 0.05), but wax removal using ethyl ether swab did not (P > 0.05). Aphids initiated signif icantly more probes on Border oar leaves than on Morex barley irrespective of wax removal, although total probing duration per aphid was not significa ntly different among the four cereals examined. Accumulative salivation dur ation per aphid on oat leaves with wax was significantly longer than other cereal leaves with wax, while accumulative ingestion duration per aphid on Arapahoe wheat and Morex barley was significantly longer than on oat. Nymph oposition of D. noxia on cereal leaves maintained on the benzimidazole-agar medium showed that aphids produced a greater number of nymphs on Morex bar ley and less on Border oat leaves, although wax removal did not affect aphi d nymphoposition. Removal of leaf epicuticular waxes from the 4 cereal geno types using ethyl ether swab indicated that the influence of wax on plant r esistance to D. noxia probing and reproduction was limited. Morex barley wa s the most favorable, while Border oat was the least favorable cereal host of D, noxia.