A SURVEY OF FIELD PEA DISEASES IN ALBERTA IN 2019

A survey of 124 field pea crops in Alberta in 2019 revealed the prevalence, incidence and severity of root rots and mycosphaerella/aschochyta blight. Additionally, white mould and bacterial blight symptoms were evaluated in 90 and 87 fields respectively. Prevalence, incidence and severity of root rots were slightly higher when compared with the 2018 pea disease survey, but 2019 results are very close to the long-term average. Levels of mycosphaerella/aschochyta blight were higher than those observed in 2018, and higher than the long-term average. INTRODUCTION AND METHODS: Since 2006, surveyed pea crops (Pisum sativum L.) in Alberta have shown significant damage from root rot caused by Fusarium spp. (Chang et al. 2006). Additionally, the root rot pathogen, Aphanomyces euteiches Drechs., was confirmed in Alberta fields in 2013 (Chatterton et al. 2014). These root rot pathogens have caused significant losses to pea producers (Chatterton et al. 2019). Additionally, foliar blights and stem rots, such as those caused by Mycosphaerella pinodes (Berk. & A. Bloxam) Vestergr., Pseudomonas syringae pv. pisi Sackett, and Sclerotinia sclerotiorum Lib. de Bary are potentially damaging pathogens that can be easily observed, visually, in the field. A survey of diseases on field pea was performed in Alberta in 2019 with the goal of assessing or monitoring diseases of peas which could be visually rated in the field. A total of 124 crops were surveyed all across Alberta for these pathogens. Surveys were conducted at the early flowering stage (mid-June to July). At each field site, 100 pea plants were examined for symptoms. Ten plants were collected from 10 sites in a W-shaped pattern, with at least 30 m between sampling sites. All plants were rated for root rot and mycosphaerella blight using the 1 to 7 scales shown in Tables 1 and 2. Prevalence was calculated as percentage of fields positive for the pathogen, while incidence represents the percentage of plants positive for the pathogen. Severity was calculated as an average rating of the values obtained using the respective disease severity rating scales. RESULTS AND COMMENTS: The overall prevalence of root rots in the province was 92.7%, while the average root rot incidence was 64.7% with an average severity was 2.6 (Table 3). Mycosphaerella blight was present in 80.6% of fields with average incidence and severity of 65.8% and 2.2, respectively. Root rots levels were very similar to the 5-year average, while mycosphaerella blight was higher than the average (Table 3). Sclerotinia white mould was observed in 14.4% of fields with an incidence of 0.6% while bacterial blight was observed in 21.8% of fields at an incidence of 10.7% (Table 4). [GRAPHICS]