Field surveys for pea root rot performed across the province in 2013 and 2014 revealed the presence of the previously unreported pathogen Aphanomyces euteiches in Alberta (Chatterton et al. 2014). A. euteiches is the most destructive pathogen to pea worldwide; control measures are difficult, owing to the longevity of resting spores (Gangneux et al. 2014), and thus its detection has raised serious management implications for pea producers. Surveys of fields in 2013 indicated that A. euteiches was detectable in seven out of 145 fields within > 200 km radius in southern Alberta. However, the number of fields that tested positive in 2014 increased significantly (77/131 fields tested), and were found throughout pea growing regions.
Fields that tested positive for A. euteiches often had the highest root rot ratings (6 – 7, indicating dead or decayed root system). Several fields showed complete yield loss; shoots were yellowed and stunted with premature lodging, and were often sprayed out before harvesting. Producers in counties with widespread root rot have indicated that they would no longer consider growing peas in their rotations, until solutions to manage the problem are available. The widespread distribution of this soilborne pathogen would imply that the pathogen has been present, but gone undetected, for a number of years, partly because formal surveys, including a pathogen isolation component, hadn’t been conducted for several years, and stresses the importance of surveillance activities to predict disease impact.
The natural host range of this pathogen in Alberta is not known, but it is suspected that alfalfa fields may also be infected in Alberta. Preliminary greenhouse trials on host range of Alberta strains indicated that alfalfa, lentils, and some dry bean cultivars are susceptible, and that soybean, faba beans and chickpeas are resistant. However, artificial inoculations in the greenhouse are not always indicative of host range in natural environments. Therefore, a thorough survey of potential host crops throughout Alberta is required to determine the potential threat of Aphanomyces root rot to all pulse/legume crops.
Objectives:
- Determine distribution of Aphanomyces root rot on pulse and forage legume hosts
- Evaluate soil characteristics (soil compaction, pH and nutrient) contributing to root rot severity
- Determine host range potential of Aphanomyces euteiches isolates from Alberta on pulse and legume crops