<i>Aphanomyces</i> root rot of peas 3. Control by the use of cruciferous amendments

Abstract

Abstract Growing Brassica napus in Aphanomyces euteiches infested soils for four months reduced the disease severity index (DSI) from 58 to 27, 72 to 53, and 81 to 56 for each of three soils tested. Over the same period there was no change in DSI when Triticum aestivum, Trifolium repens , or no plants were grown in the same soils. When dried leaves and stems of five cruciferous species were incorporated (0.5% of the soil dry weight) into infested soil, there were significant reductions in DSI and oospore numbers. The reductions were greater after six weeks of incorporation compared to three weeks. With soils of DSI 50, 75, and 100, Brassica napus, Raphanus sativus , and Sinapis alba were equally effective, reducing DSI by 32 – 38% and oospore numbers by 66 – 72%. When the same five species were grown for six months in infested soils and the roots alone were incorporated in the soils for six weeks, there was an average reduction of 41% in DSI and 56070 in oospore numbers by Brassica oleracea, Brassica napus , and Raphanus sativus . This cultural method, by reducing inoculum, appears to be of value in the control of Aphanomyces root rot of peas ( Pisum sativum ).