Lettace Root Aphid Control by Means of Plant Resistance

SUMMARY At Wellesbourne, Warwick, in 1968, not all plants of the lettuce cv. Webb's Wonderful protected against lettuce root aphid. Pemphigus bursarius (L.), by diazinon pre‐sowing treatments remained uncolonized throughout a relatively light aphid attack but no colonization of unprotected plants of cv. Avoncrisp occurred. In a second experiment in 1972, in which plants were untreated and exposed to an intense aphid attack, the lettuce cvs. Mildura, Borough Wonder, Webb's Wonderful, Avoncrisp and Avondefiance all attracted similar large numbers of winged root aphid rnigrants. No root colonies formed on the resistant CVS. Avoncrisp and Avondefiance. All plants of the other cultivars became severely damaged and most were killed.