Source: University of Minnesota Extension
Things are relatively quiet and the overall the small grains are looking very good.
Scouts continue to find tan spot in both winter wheat and spring wheat in their third week of scouting. Although the scouts have not encountered any leaf or stripe rust, others have found it in research trials on the St. Paul campus. Likewise, I have positively identified Septoria spp. in both oats and spring wheat in a few fields. The reported incidence in all cases has been relatively low. Tan spot severity is by far the highest in wheat on wheat.
The risk assessment models for all three leaf diseases have been trending higher this past week across most of the State. The immediate forecast suggests that this trend will continue.
The earliest seeded oat has or soon will reach Feekes 9 when the flag leaf has fully extended. There are enough parallels with leaf rust to suggest the risk of crown rust is on the rise. The buckthorn in my yard is covered with aecia that produce the aeciospores that will start the crown rust (Photo 1).
A full labeled rate at Feekes 9 of a labeled fungicide provides the best protection against crown rust as many oat varieties are susceptible to very susceptible to crown rust.
The risk model for FHB continued to trend low for much of the State, largely because of the cooler temperatures rather than the absence of precipitation. Only the southeastern corner of the State has seen a persistent risk of moderate to high risk of FHB.
The immediate forecast indicates that the risk of FHB will be increasing across the state. The earliest seeded spring wheat will be heading the coming week in the southern half of the State. Keep an eye on the risk models and consider a fungicide treatment at Feekes 10.51 or beginning of anthesis if the risk models continue to trend towards moderate to high risk.
Photo 1 - Aecia of crown rust on common buckthorn (Rhamnus cathartica L.)
Aphids migrated a little further north and have reached the southern Red River Valley. The scouts have not found a field at or even near the treatment threshold of 80% of the stems having one or more aphids prior to heading.
Wheat stem sawfly adults continue to be found in the emergence traps on the NWROC, but numbers have been dwindling.