b'PLANT DISEASERotten RootsRoot rot in peas caused by Aphanomyces has become an increasing problem in fields across southern Alberta over the last decade.IN 2012, a new problem emerged on Prairie fields. The leavesof samples of soil from roadsides have found to be infected with on pea plants were yellowing just above the ground, there was aAphanomyces, leading researchers to believe Aphanomyces has pinching of the stem right at the soil surface and the roots werealways been present in the soil.a honey brown colour. Yields in infected fields were droppingIts been naturally occurring, but some of our cropping anywhere from 30 to 50 per cent. practices over the last 30 to 40 years have multiplied the Many were writing it off as fusarium infection. But no, therepathogen significantly, Ippolito says.was another plant disease sitting in the soil and stalking its preyAphanomyces. Fighting Aphanomyces in the FieldsIn a lot of cases, we visually identified Aphanomyces orAphanomyces pops up in wet years. The pathogen likes wet fusarium regularly. And in looking back, we probably justconditions as it is a water mold and needs excessive moisture to wrote it off to be fusarium and not looked any deeper, saysmove to the roots, Ippolito explains. Peas, along with lentils, dry John Ippolito, crops extension specialist with the governmentbeans and alfalfa, act as a host crop for it.of Saskatchewan. One of the problems with Aphanomyces isWere finding (Aphanomyces) is more prevalent on clay loam we really have to go to kind of a molecular type lab analysis toand clay soils that have less drainage or not perfect drainage. determine that Aphanomyces was present. And then compaction, in Western Canada anyways, were really In 2012, the first fields of peas infected with Aphanomycesfinding compaction is also a contributing factor, Ippolito explains.were identified in Saskatchewan. In the nine years since then,With Aphanomyces still being a relatively new threat more fields across Saskatchewan and into Alberta have beento Prairie fields, the main recommendation to fight back diagnosed with the disease and farmers have found themselvesagainst the pathogen is to stretch out crop rotations. Before searching for ways to fight it off. Aphanomyces was identified, most farmers were using a four-Even though it only was identified in the last decade, there isyear rotation for peas, but now it is recommended to switch to proof its been on the Prairies for much longer than that. Testsa six or even an eight-year rotation. There are still pulse crops A field where the plants in it have been infected with Aphanomyces. PHOTO: SHERRILYN PHELPS, SASKATCHEWAN PULSE GROWERS62seed.ab.ca'