Sensibilite des racines et tubercules des varietes de pommes de terre a la gale poudreuse et quelques resultats de lutte chimique

摘要

Field susceptibility of roots, stolons and tubers of potato cultivars to powdery scab was examined. With some exceptions (Markies or Santana), cultivars susceptible to tuber contamination were also sensitive to root contamination (e.g. Agria, Erntestolz and Iroise). Disease frequency and intensity was related to trial location, as areas with cool weather and moist soil conditions are favourable to powdery scab. The occurrence of disease varied from one year to the other, but the ranking of cultivar sensitivity remained the same. Inoculum appeared to be irregularly distributed in soil. Wide differences in disease occurrence were observed between plots. The mop-top virus (PMTV) is transmitted by powdery scab. Occurrence of PMTV symptoms was irregular and the sensitivity of cultivars to the virus was not correlated to that of powdery scab. Chemical treatments of infected seed tubers were not efficient. In-furrow soil treatments with fungicides at planting reduced disease symptoms on tuber progeny.