The association of <i>Pythium</i> spp. with cavity spot and root dieback of carrots

Abstract

SUMMARY The possibility of an association between cavity spot and root dieback of carrots has been demonstrated, along with control of both disorders by soil sterilisation with methyl bromide or seed and soil treatment with metalaxyl. When carrots were grown in sterilised soil into which five Pythium spp. were introduced individually, cavity spot occurred and the Pythium spp. were re‐isolated from cavities. The relatively slow growing Pythium violae gave the highest percentage of carrots with cavities. In a laboratory test a range of Pythium spp. produced cavities on carrots previously grown in sterilised soil, and with one exception were re‐isolated from those cavities.