Stripe rust brought spores and surprises to Alberta growers and researchers this year.
The yield-limiting infection usually blows in from the Pacific Northwest, first affecting winter wheat fields in southern Alberta and then spreading into spring wheat.
This year, the leaf disease overwintered in central Alberta, where it later caused an estimated 25 percent loss in susceptible varieties of spring wheat, said Alberta Agriculture cereal pathologist Kequan Xi.
Winter wheat acreage is low in central Alberta, and the few crops that are grown there are often monitors for any stripe rust infection that could affect the much larger spring wheat acreage.
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This year, Xi said stripe rust was seen in the tillering stage of spring wheat, resulting in fungicide spraying in mid to late June, two weeks earlier than usual.
Infection has also been significant in the province’s Peace region.
The disease was also found in several fields across a wide swath of southern Alberta, which is the usual bellwether for the pathogen. However, its appearance was patchy and infection generally not severe.
Thirty percent of fields surveyed for the disease had moderate to severe levels of infection. Fungicide spraying took place in winter and spring wheat fields in some areas, but most crops are now too mature for fungal spraying.
“Any growers who had susceptible or moderate resistance (in wheat varieties) probably sprayed,” said plant pathologist Mike Harding of Alberta Agriculture.
Most effective fungicides require a specific pre-harvest interval, so Harding recommended checking product labels and the provincial crop protection guide, known as the blue book, before spraying at this stage.
Agriculture Canada researcher Denis Gaudet, who has been surveying southern Alberta fields for the pathogen, said overall damage will likely be limited.
“I think that we won’t get hit hard with stripe rust in terms of yield and quality damage this year,” he said.
Stripe rust is characterized by long, bright orange stripes on the upper leaves of wheat. The fungus reduces plants’ ability to photosynthesize and also releases spores that rupture the plants’ epidermis. That results in moisture loss and death from dehydration.
Gaudet said producers who are considering planting winter wheat should choose stripe rust resistant varieties.
Radiant used to be the go-to variety, but its resistance has broken down as disease pathogens have changed.
Gaudet recommended Moats for dry land regions of Western Canada Flourish or AAC Gateway for irrigated land and the parkland region. All three have resistance to stripe rust and similar levels of hardiness.
Given the unpredictability of stripe rust infection in any given year, it might also be wise to consider resistant spring wheat varieties next spring as well, added Xi.
Gaudet said the breakdown of resistance in varieties that are bred to fend off stripe rust is a concern among researchers and the focus of new crop breeding.
Development of new winter wheat varieties with strong resistance would also prevent later spread and infection to spring wheat.
