ISSUE 6 June 8, 2000
POTATO LATE BLIGHT HOT LINE
The potato late blight hot line is in operation again this year. It provides late blight severity values for 22 sites in North Dakota and contiguous Minnesota; 15 are non-irrigated sites and 7 are irrigated sites. In addition to the severity values, NDSU recommendations are also provided. The hot line is updated every Monday, Wednesday and Friday . The hot line can be reached by telephone at: 1-888-482-7282. It is also available on the Web at:
CANOLA SPRAY DECISIONS FOR SCLEROTINIA MANAGEMENT
The decision to use a fungicide for Sclerotinia management is never
easy due to the cost of registered fungicides. Conditions favoring Sclerotinia and an
economic return include plentiful rainfall leading up to flowering, a dense canopy, and a
forecast of continued wet or humid weather after the application. Yield potential should
be 1,500 lb/A or more. Most Canadian recommendations stress a yield potential of 1,500
lb/A. With sagging oilseed prices, we need to consider the cost
of fungicide more closely. If the cost is less than $20/A a yield potential of 1,500 lb/A may be considered if disease potential is high, but if the cost of fungicide is more than $20/A a yield potential of at least 2,000 lb/A is needed for the likelihood of an economic return.
For producers near the Canadian border, the Web site of the Canola Council of Canada provides useful information at http://www.canola-council.org. Click on "Weather and Crop Forecasts" then click on "Sclerotinia Risk Maps". These risk maps are updated twice a week, beginning in mid-June.
Another decision aid is the Sclerotinia Risk Assessment, which is reproduced, by permission of the Canola Council of Canada, in North Dakota Extension Report 54, by Arthur Lamey and Richard Meronuck. The risk assessment is also available on the Canola Council of Canada Web site.
Extension Plant Pathologist
SMALL GRAIN DISEASE SURVEY
Wheat leaf rust detections: Wheat leaf rust was detected in winter wheat plots at Casselton on May 31, by Dr. Jim Miller, USDA Cereal Rust Pathologist, Fargo. He found trace amounts in plots of Roughrider, Seward, Northstar, and Nekota winter wheat varieties. Greg Endres, Area Extension specialist at Carrington, and Tom Olson, Stutsman Co. Agent, found trace amounts of wheat leaf rust on June 1, in a commercial field of winter wheat in Stutsman Co.
So wheat leaf rust has found its way to ND now, but still in very low amounts. As the latest Cereal Rust Bulletin # 5 (June 6) states: "The timing of this rust development in North Dakota is the same as last year when leaf rust became more widespread in the upper Midwest than in the past 20 years".
Barley yellow dwarf virus (BYDV) was detected in Sargent Co. on May 31 by Matthew Gregoire and Marcia McMullen. Most of the winter wheat fields surveyed showed scattered infections, with the typical bright yellowing of the leaves, from the tip downward, and some with stunting, as well. We found a few English grain aphids and greenbugs, but really had to hunt for them, so populations of grain aphids are still very low. Amy Dukart, field scout in the southwest, also found BYDV this last week, in a winter wheat field and in a barley field in Adams County.
The detection of BYDV but low populations of aphids, plus the detection of leaf rust, indicate a "wait and see" approach for now, but also the need for careful and frequent monitoring for cereal aphids and rust development! The later planted small grain crops will have the biggest risk for these two diseases.
Other disease observations this past week: Tan spot was the most common disease observed on wheat across the state. Jerry Schneider found mostly tan spot in central counties, with tan spot confined to bottom leaves in spring wheats, and some infections on mid-leaves in a winter wheat field. He also saw a few aphids here and there. Greg Endres, Area Agronomist at Carrington, and Kent Aldrin, Sheridan Co. Agent, observed some severe tan spot on 3 leaf wheat in a field of wheat planted into wheat stubble.
In the south east area, Matthew Gregoire found tan spot to be common on winter wheats, even with a few infection spots on the flag leaf. Spring wheats in this region were relatively disease free.
In the north central area, Alison Marsland very low levels of tan spot on lower leaves of durum wheat, plus some low incidences of root rot on durum.
Amy Dukart also found tan spot to be the most common disease observation on spring wheat in southwestern counties. She also found net blotch in barley, and a field with WSMV symptoms in Hettinger Co.
Extension Plant Pathologist
WHEAT DISEASE FORECASTING SYSTEM
The NDSU wheat disease forecasting system will once again be
operational this season. Forecasts will be provided for scab, tan spot, Stagonospora
(Septoria) blotch, and - new for this year - wheat leaf rust. All diseases will be
forecasted for locales surrounding 17 NDAWN stations in the Red River Valley and the
northern tier of counties in North Dakota. In addition, leaf diseases only will be
forecasted at seven NDAWN sites - Cando, Carrington, Crary, Dazey, McHenry, Prosper, and
Wyndmere. The system may be accessed on the web at
or by telephone at 1-888-248-7357 (231-6601 in Fargo calling area).