Control measures urged to keep diseases from spreading

LETHBRIDGE — Bumper crops made headlines across the Prairies last year, but plant diseases also reared their smutty heads.

“The single most important factor that affects the development of infectious diseases is the weather,” said Ron Howard of the Alberta Crop Development Centre in Brooks, Alta.

Mike Harding, a plant pathologist with Alberta Agriculture, warned that 2014 could be another bad year.

“We have had three years in a row where we have had a significant reservoir of diseases,” he told the Irrigated Crop Production Update in Lethbridge Jan. 21.

Harding said Alberta weather was variable last year.

Some parts experienced the wettest growing season in 50 years while most of southern Alberta was near normal or moderately high for precipitation.

“There were a lot of situational things going on, so not everyone had the same environment, even if they were living within 20 miles of each other,” he said.

Climate change could increase disease severity or cause more warm weather infections to occur. Infected plants, equipment, containers that hold plants, agricultural machinery, insects or wind could introduce new troubles.

“Soil moving on machinery is one of the main ways we are getting fields infested with clubroot in canola,” Howard told the conference.

Stripe rust, fusarium and Goss’s wilt of corn were diagnosed last year.

Stripe rust on wheat and barley was found in several regions.

The disease thrives in cool nights and can reduce yields by 70 percent if not controlled. Spore showers on the wind usually come from Washington, Oregon and California.

It is spreading north and east on the Prairies into Saskatchewan, Manitoba and Alberta’s Peace River district.

Fusarium likes warm, humid conditions. New strains are occurring that produce more toxins and may be even more infectious.

“It was first found in Manitoba, but in the past two decades it has moved westward and is now established in southern Alberta,” Howard said.

Last year was ideal for fusarium head blight and ergot, according 
to Canadian Grain Commission surveys.

Southern Alberta crop districts had different strains of fusarium. It usually occurs in two to 10 percent of samples, but it was as high as 20 to 25 percent last year.

The disease was also detected in central Alberta along the Highway 16 corridor.

“It is not commonly found outside irrigated Alberta,” Harding said.

“There is reason to believe that could be changing.”

Northern Alberta saw a few confirmed cases last year, but it is rarely found in that region.

Ergot cases spiked in Canadian western red spring wheat in 2012 and increased slightly last year in some isolated regions.

It often starts in ditches, so farmers should mow down grass before it heads.

“We don’t have any technology that we can buy and spray on them to reduce ergot,” Harding said.

Goss’s wilt in corn was seen for the first time in Alberta last year. It was discovered in Manitoba in 2009 and has spread throughout the province.

Last year it was found in five of 45 fields that were surveyed in Alberta.

Canola producers continue to fight against clubroot and blackleg.

New blackleg strains are challenging disease resistant varieties. A large provincial survey is underway to track it and discover what strains are present.

Clubroot affects canola, mustard and other members of the cabbage family and has been found at varying levels in 24 Alberta counties. Some infested fields have been found in Saskatchewan and Manitoba. It was first seen in 12 fields in 2003 and was up to 1,500 positive fields in 2013.

“There are probably significant fields that have not been detected,” Howard said.

Verticillium wilt cannot be controlled with fungicides. It does well in the southern Alberta environment and could easily establish without variety resistance or chemicals to control it.

Alberta pulses are seeing more blight, although it usually needs higher temperatures and more humidity to establish itself.

Peas are susceptible to root rot. A 2013 survey looked at 150 fields in Alberta and found most had root rot of various types

Aphanomyces root rot was seen in sugar beets, but no one is sure if it has crossed over to peas.

“Some fields were literally hammered with root rot, and in other fields it wasn’t common,” Harding said.

Late blight occurs worldwide in potatoes, and outbreaks started in 2010-11 in Alberta. It started in garden tomatoes and has the potential to spread to commercial potato production through seed.

“We are really aiming at the home gardeners and market gardeners to control their seeds,” Howard said.

Cereal diseases were prevalent last year, said Harding, including barley scald, net blotch and tan spot and septoria and stripe rust on wheat.

A disease survey in central Alberta found a 65 percent incidence of scald, ranging from mild to serious. The situation was probably similar in the south, said Harding.

“They found net blotch in every barley field they visited.”

There was a 25 percent incidence of barley spot splotch and about the same amount of stripe rust in winter wheat fields, he said.

However, the incidence was low enough in many cases that it did not need to be sprayed with fungicide.

As well, loose smut was found on barley and a variety of wheat leaf diseases such as septoria, tan spot and stagonospora.

“These are the dominant pathogens we see on wheat. There were lots of examples in wheat fields where there was disease pressure,” Harding said.

Sclerotinia is seen every year and is common on irrigated areas. Plant scientists thought it would be a lot worse, but it was not as serious as expected in canola and dry beans.