Issue # 3, June 14, 2000

• Crops In Standing Water
• Fungicide Applications For HRSW
• Water Trivia
• Canola Spray Decisions For Sclerotinia Management

Crops In Standing Water

    Heavy rains on June 13 - 14 produced a lot of standing water. How long can a crop survive in flooded conditions is environmentally dependant. Under cool cloudy conditions, soybeans: about 3 days, drybeans: about 1 day, and corn: 2 to 3 days. Under sunny and warm conditions, soybeans: 1.5 days, drybeans: ½ day, and corn 1 to 1.5 days. As temperature and sunny conditions increase, the amount of time decreases.
    Soybeans become nitrogen deficient and also susceptible to iron chlorosis under flooded conditions. Phytophthora root rot in susceptible varieties is frequently associated with flooding damage. Flooding causes anarobic conditions (lack of oxygen) which will cause root damage. As flood waters subside, plants may start to appear normal but will be stunted and yield losses may occur.

Fungicide Applications For HRSW

    Griggs County has had its share of disease problems over the last several years and the current wet conditions have increased the possibility of diseases for 2000.  To determine if a fungicide application will be of benefit, look at the following factors.  First of all is the current price of wheat.  At this time, prices are not the most attractive.  Second, look at the crop stage and any disease pressure present.  Third, is this crop on recropped ground or next to last years wheat crop.  Fourth, what variety is being grown.
    Determining what disease you will be treating for is important due to the timing of the application.  For most foliar diseases, the optimum time to spray is when the flag leaf is elongated about 3/4 of its final size.  For scab, the optimum time is at early flowering.  Research has shown leaf disease suppression with the late application (early flowering) is past years.  But, if there is a high presence of leaf diseases prior to flag leaf emergence, an early application might be more beneficial.  Yield increases for foliar applications for leaf diseases have been shown to have around a 10% yield increase.  If there is not a 40 bushel or more yield potential, fungicides have not been known to pay for themselves.  Under heavy scab situations, a fungicide application might be beneficial due to increased grain quality.
    There are several good products on the market.  Quadris, Tilt and mancozeb products, all have good leaf disease control.  For scab control, Quadris and tilt have been the sprays of choice.  For more information on sprayer setup and scab suppression, contact the following site: 
http//www.ext.nodak.edu/extpubs/ageng/machine/ae1148w.htm

Water Trivia

    The recent rains have caused major flooding in some areas in eastern North Dakota. I was curious how many gallons of water did we receive? Doing the math, a one inch rain will yield the following:
27,150 gallons water per acre
4,344,000 gallons per quarter
17,376,000 gallons per section
625,536,000 gallons per township

Now lets look at a five inch rain:
135,750 gallons per acre
21,720,000 gallons per quarter
86,8800,000 gallons per section
3,127,680,000 gallons per township

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. 

Art Lamey
Extension Plant Pathologist

Please Contact Our Office For Additional Information
E-mail: griggs@ndsuext.nodak.edu
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