ISSUE 17 September 28, 2001
SMALL GRAIN DISEASE SURVEY, 2001
Approximately 1500 spring wheat, durum and barley fields were surveyed by the NDSU IPM field scouts in 2001. The majority (958 or 64%) of the fields surveyed were hard red spring wheat.
Leaf rust was detected in 22% of the 958 spring wheat fields surveyed. The most frequent detections were in the south central and central areas of North Dakota. The average severity in infected fields was 8.5%; the average severity across all fields was 1.9%. Leaf rust was not detected until July 5, in LaMoure and Dickey counties. Leaf rust did not have significant impact on yields in 2001, except perhaps for a few late planted fields of susceptible varieties.
Tan spot was found frequently in spring wheat and durum wheat and was the most common disease observed prior to heading stages. For crops surveyed past heading, tan spot was found in 54.7% of the spring wheats and 63.1% of the durum fields. Tan spot severity on flag leaves of headed crops averaged 6.9% in spring wheat and 7.5% in durum wheat.
Septoria leaf blotch was observed most frequently after head emergence. Of fields surveyed past flowering stage, 78% of the spring wheat fields had Septoria symptoms, and 85.3% of the durum wheat fields had Septoria symptoms. Average severity on the flag leaf in infected spring wheat fields was 10.9%, while in durum wheats, Septoria severity averaged 18.9% on flag leaves of plants past flowering stage.
Scab (Fusarium head blight) was observed in 70% of both spring wheat and durum wheat fields past the flowering stage. Average severity of scab in spring wheats was 4.0% (range 0.1 - 34.2%), while average severity of scab in durum wheats was 7.2% (range 0.1 - 80%). The most severe scab was found in the north central and northwest districts.
Scab levels observed in barley were low, with 37.1% of the headed fields showing symptoms, but the average severity was less than 1%.
Diseases such as flag smut and dwarf bunt were not observed in the survey. The virus diseases, wheat streak mosaic and barley yellow dwarf, were very infrequent, as were black chaff and ergot. Loose smut was observed in 43% of the headed barley fields, and severity ranged from 2 - 14%. Loose smut was found in 29.9% of spring wheat fields, and severity ranged from 2 - 34%, with 2-4% most common.
2001 CANOLA DISEASE SURVEY
Almost all data on the 2001 canola disease survey has been received and summarized. Area specialists and county agents/educators surveyed 45 fields in Minnesota and 248 in North Dakota for a total of 293 fields. Thus, each field surveyed represented approximately 5,000 acres of canola.
Aster Yellows was present, but at low to undetectable levels in most fields in Minnesota and North Dakota. Average incidence was 2.2% in Minnesota and 1.9% in North Dakota, compared to the 2000 incidences of 3.9% in Minnesota and 4.5% in North Dakota.
Blackleg incidences in 2001 were comparatively low, 1.6% in Minnesota and 1.8% in North Dakota. This compares with 0.5% in Minnesota and 2.8% in North Dakota in 2000. Incidences in individual fields were as high as 37.5% in one field in Cavalier County, ND and 47.5% in one field in Towner County, ND. However, severely infected fields were widely scattered, and many fields had no detectable levels of blackleg.
Sclerotinia stem rot was the most common and serious disease in 2001, as it has been each year from 1993 to 2000. Average incidences were 14.1% in Minnesota and 14.3% in North Dakota in 2001, much lower than the 2000 incidences of 17.8% in Minnesota and 17.0% in North Dakota. However, there were dramatic differences in Sclerotinia in the various crop reporting districts of North Dakota in 2001, with 32.0% reported by Greg Endres for the Central District (Eddy, Foster, Sheridan, Stutsman and Wells counties) and 18.1% for the Northeast District (Cavalier, Nelson, Ramsey and Towner counties), compared to the state average of 14.3% (Figure 1).
There were 15.6% of surveyed fields in Minnesota and 13.% of surveyed fields in North Dakota with an economic loss in 2001. An economic loss is defined as over 30% Sclerotinia, which represents a yield loss of approximately 21%. Although this high a percentage of fields with an economic loss represents serious economic losses, it is much less than the 22% in Minnesota and 21% in North Dakota in 2000. The percent of fields with an economic loss varied greatly, from 46.2% of surveyed fields in the Central District of North Dakota and 22.6% in the Northeast District to none of the fields in the Northwest, West Central and Southwest Districts (Figure 2).
The above data indicates that economic losses were very common in the Central District and common in the North East District.
Alternaria Black Spot severity was 0.37% in Minnesota and 0.66% in North Dakota in 2001. These figures are similar to those for 2000, indicating that there were no losses to this disease in most fields.
NDSU Plant Pathologist Emeritus