The symptoms and causal agents of early‐dying disease ( Verticillium wilt) of potatoes

SUMMARY The only characteristic symptom produced by Verticillium albo‐atrum and V. dahliae in infected potato plants is unilateral chlorosis and necrosis: this was not shown until the approach of host maturity, and was distinguishable from symptoms of natural senescence only in its slightly earlier expression. Of six species of Verticillium tested against potato (King Edward), V. albo‐atrum, V. dahliae, V. nigrescens and V. nubilum were pathogenic (all produced ‘wilt’ symptoms and relative virulence was in that decreasing order) but V. tricorpus and V. lateritium did not induce disease. Isolates of V. albo‐atrum and V. dahliae , obtained from a number of other host plants, were also pathogenic to potato. Possible reasons are given for the fewness of records of ‘Early dying’ disease ( Verticillium wilt) of potatoes in the field.