Pest and Disease Survey Results

Summer surveys reveal pest and disease pressure on pulses for 2017

by Trudy Kelly Forsythe

Saskatchewan Pulse Growers and the Saskatchewan Ministry of Agriculture (SMA) conducted pest and disease surveys this summer to see exactlywhat pulses were encountering in the field.

Peas and Lentils

Pea and lentil root rot levels were specifically monitored through a root rot disease survey conducted with samples collected from 100 pea crops and 93 lentil crops in Saskatchewan in June and July. The samples were sent to Dr. Syama Chatterton,
Research Scientist at Agriculture and Agri-Food Canada’s lab in Lethbridge, for analysis, which revealed that 100 per cent of the pea and lentil crops had at least trace levels of root rot.

Keeping in mind that a severity rating of less than three is considered healthy, incidence of root rot, where the number of plants assessed within the field with root rot severity of greater than three was highest in peas at 43 per cent and lowest in lentils at 9.5 per cent.

In addition to the root rot survey, Barb Ziesman, the Provincial Specialist, Plant Disease with SMA, lead the Ministry’s specific lentil disease survey to evaluate other diseases, from late July to early August, in 52 lentil crops. In this second survey root rots were again identified, and 54 per cent of the lentil crops evaluated had the root rot complex, with highest prevalence in the southwest.

The lentil survey evaluated foliar diseases as well and found Anthracnose to be the second most prevalent followed by Stemphylium blight. Anthracnose was found in 38 per cent of lentil crops across Saskatchewan. Stemphylium blight was found to be present in 33 per cent of all fields. White mould was present in only two per cent of surveyed crops while grey mould was absent.

“Generally speaking, disease levels were lower in 2017 compared to 2016,” Ziesman says. “A major reason for this is the dry conditions experienced across most of the province this year.”

This makes sense since disease development is largely driven by the environmental conditions, and most fungal diseases favour wet conditions.

Year-to-year variations are largely due to differences in environmental conditions during the growing season. As a result, disease management decisions need to be made during the growing season by scouting crops and assessing disease risk.

Changes in disease incidence year-to-year are common because disease is the result of the interaction between the pathogen, the environment, and the host. “Most diseases are favoured under wet conditions,” explains Ziesman. “The level of disease in field the last time a susceptible crop was grown may also influence the amount of pathogen present to cause disease.”

Chocolate Spot

Foliar lesions were present in 100 per cent of the 21 faba bean fields surveyed this year, although the severity of infection was low in all fields. Processing of the samples at Dr. Chatterton’s lab has identified Botrytis spp. in 20 per cent of all samples collected from Alberta and Saskatchewan, while the identification process is still underway.

Pest Findings

Dr. Sean Prager, an Assistant Professor and entomologist with the Department of Plant Sciences at the University of Saskatchewan, and Dr. Meghan Vankosky, a Research Scientist in field crop entomology at Agriculture and Agri-Food Canada, were both involved in insect pest research in 2017. 

“The most common insects in faba beans, and many of the other surveys, were aphids,” Prager says, explaining they found mostly pea aphid, but clarifying they were not really doing detailed identification work.

Lygus bug numbers were rather low, with most found in samples from southeastern Saskatchewan, and very light sampling for wireworm found no larvae at all.

“Pea leaf weevil was lower than expected but range expansion was occurring at the same time,” Vankosky says. “Additionally, they were worse in faba beans than in field peas. There were reports they moved into soybeans in the fall, but they were not likely associated with yield loss.” Prager and Vankosky add that it is their impression that weather was a much larger factor in losses than any of the common insects. 

Looking Ahead

There are a number of considerations growers should keep in mind heading into the next growing season. First, it is important for growers to know their disease risk. This means knowing the level of susceptibility of the variety being planted, the pathogen presence, and the history in the field.

“Within the growing season, make sure to scout regularly,” says Ziesman. “Fungicides are not required every year and fungicide application decisions should be based on disease risk which will be influenced by environmental conditions.”

As for pest control, Prager says the provincial maps will be available from the government and Prairie Pest Monitoring Network Blog in January. "They are the best available tools for planning,” he says. “We also recommend talking to the local  professional agronomists.” 

Scouting remains important and producers should consult the previous year’s results as a guide to which insects to scout for. Watch the Prairie Pest Monitoring Network’s blog for weekly updates during the growing season.