Winter survival of stripe rust
By Top Crop Manager
Researchers with Alberta Agriculture and Rural Development (AARD) and Agriculture and Agri-Food Canada (AAFC) are continuing to monitor plots and a few fields for stripe rust survival throughout the winter and early spring.
Evidence of overwintering stripe rust was reported by AARD cereal pathologists Dr. Kequan Xi and Dr. Krishan Kumar in 2013-2014 in central Alberta. This winter, Dr. Denis Gaudet, research scientist with AAFC in Lethbridge, Alta., has extended his stripe rust survey to include some winter evaluations in southern Alberta.
Gaudet reported that eight winter wheat fields in the southwestern region of the province (Lethbridge, Cardston, Raymond and Coaldale) were surveyed on December 12, 2014.
According to Michael Harding, research scientist - plant pathology in Brooks, Alta., stripe rust levels of five per cent were observed in two fields and trace levels in a third field.
"Stripe rust was widespread in volunteer winter and spring wheat throughout the region," notes Harding. "It was apparent that stripe rust had infected winter wheat that was seeded from early to late September (ie Zadoks stage 21), but later seeded winter wheat (Zadoks stage 1) remains clean. Stripe rust was also widespread in winter wheat research plots."
Xi had also noticed the effect of seeding date on stripe rust infections of winter wheat. His limited survey results from central Alberta showed that the degree of stripe rust severity or prevalence appeared to be more associated with seeding time of winter wheat than cultivar resistance ratings during fall surveys (at the seedling stage). More specifically, an early seeded field (i.e before early September) tended to have more stripe rust than late seeding (i.e. after early September), regardless of genetic resistance ratings of each cultivar.
The early seeding effect observed by both researchers is likely due to the fact that stripe rust spores were in the air in early September, but not later in the month. Therefore, leaves of the later seeded plants escaped disease because they had not yet emerged and could not be infected. The difference in severity between resistant and susceptible cultivars becomes apparent later, in early spring.
Gaudet says his group will be monitoring plots and a few fields for stripe rust survival throughout the winter and early spring. He also noted the presence of stripe rust in the three winter wheat fields in southern Alberta does not necessarily mean the stripe rust pathogen will be able to survive overwinter in those fields. If any overwintering survival of the stripe rust pathogen occurs, it cannot be detected until spring 2015.