At an wheat and seed production meeting Jan. 6, Oregon State University plant pathologist Chris Mundt warned growers that stripe rust could strike wheat early this year.
Those concerns now have materialized.
Mundt and three extension researchers issued an alert Jan. 19 informing growers that they have found stripe rust in early-planted experimental plots and commercial fields, beginning with sightings Jan. 7-12, three weeks earlier than ever previously recorded. The alert described “early-planted fields” as those planted in September through the first 10 days of October.
The researchers found rust on individual leaves of the wheat varieties Goetze, WB 1529, Foote and Kaseberg. Also, Mundt, Extension Cereals Specialist Mike Flowers, and Willamette Valley Extension agents Nicole Anderson and Clare Sullivan reported that rust had not developed in easy-to-spot hot spots, so it may be difficult for growers to identify infected fields.
Doing so, however, may be vital for growers to maximize yields.
With mild winter temperatures creating an ideal environment for early rust development, Willamette Valley wheat could be highly susceptible to significant yield losses this year, Mundt said.
“The largest field losses occur when stripe rust starts early,” he said. “You don’t want the rust to get ahead of you.”
The researchers are recommending that fields planted prior to Oct. 15 to susceptible or moderately susceptible varieties, such as Goetze, Tubbs 06, Mary, Kaseberg, SY Ovation and LCS Art Deco should be scouted and may require an early fungicide treatment.
“Early sprays will likely not be required on resistant varieties such as Bobtail and Rosalyn,” according to the alert, “but these varieties should still be scouted to guard against the potential for new rust races to appear.”
The alert noted that December temperatures were 5 degrees above normal, and that December temperatures are “a crucial driver of stripe rust.” Mild December temperatures facilitate pathogen survival and shorten its generation time, according to the alert.
“The early start to the rust season may allow for an extra generation of disease increase, a critical factor for rapidly spreading rusts,” the alert states.
The researchers noted that rust has not been seen in later-planted, direct-tilled fields nor in the northern Willamette Valley, but that it is expected to occur in both.
“Weather in the remainder of the year can still influence rust, but the early start of the rust season suggests that vigilance be called for in 2015,” the alert states.