ISSUE 5   June 7, 2007

POTENTIAL PROFIT/ACRE WITH EFFECTIVE FUNGICIDE USE ON WHEAT

In the May 18, 2007 Nebraska Crop Watch report, Dr. Stephen Wegulo, Extension Plant Pathologist at the University of Nebraska, provided a formula to estimate the potential profit from fungicide application to control wheat diseases. Included in that formula were estimated yield potential, average preventable yield loss expected from fungicide use, cost of fungicide application, and price received per bushel of wheat.

The estimated preventable yield loss varies with favorability of weather for disease development and the susceptibility of the cultivar. Generally, the more favorable environment and more susceptible cultivar will get a higher preventable yield loss percentage, but if the cultivar is super susceptible and environment is overwhelmingly favorable for disease, this higher percentage may not be realized.

I have used Dr. Wegulo’s information in two examples below. The first is based on a 15% yield return from fungicide use; the other based on a 20% return or preventable yield loss. Both are based on a \$16.00/acre cost of fungicide + application.

Both examples do not include any price premium or discount associated with quality factors, such as damage, test weight or DON (vomitoxin levels). For example, if the correct timing of application is not made or inappropriate products or rates are used, the yield response may not achieve 15-20%, or the DON levels could be high enough to trigger a discount.

Potential Profit/Acre with Effective Fungicide Use on Wheat

If Preventable Yield Loss = 15% and Cost of Fungicide + Application = \$16.00/acre

 Yield Potential Price/Bushel Received \$4.00 \$4.50 \$5.00 ..............Potential Profit/Acre.................. 30 \$2.00 \$4.25 \$6.50 35 \$5.00 \$7.63 \$10.25 40 \$8.00 \$11.00 \$14.00 45 \$11.00 \$14.38 \$17.75 50 \$14.00 \$17.75 \$21.50 60 \$20.00 \$24.50 \$29.00 70 \$26.00 \$31.25 \$36.50

If Preventable Yield Loss = 20% and Cost of Fungicide + Application = \$16.00/acre

 Yield Potential Price/Bushel Received \$4.00 \$4.50 \$5.00 ..............Potential Profit/Acre.................. 30 \$8.00 \$11.00 \$14.00 35 \$12.00 \$15.50 \$19.00 40 \$16.00 \$20.00 \$24.00 45 \$20.00 \$24.50 \$29.00 50 \$24.00 \$29.00 \$34.00 60 \$32.00 \$38.00 \$44.00 70 \$40.00 \$47.00 \$54.00

A 20%+ preventable yield loss was observed in NDSU research studies in 2005 on moderately susceptible cultivars in areas where leaf and head diseases were common.

SMALL GRAIN DISEASE FORECASTING WEB SITES INDICATE DISEASE RISK

The NDSU Small Grain Disease Forecasting web site has been activated for 2007. This site provides information on the risk of tan spot, Septoria blotch, wheat leaf rust and Fusarium head blight (FHB = scab). A user of the site picks the NDAWN weather station closest to their field and picks the growth stage of the crop to get information on disease risk. The flowering growth stage must be picked for information on risk of FHB. The NDSU web address is:

Another web site also is available that predicts the risk of Fusarium head blight in ND and other states. This web site model is based on weather data from the NDAWN stations and other weather data. This site, sponsored by the US Wheat and Barley Scab Initiative, can be found at:

The NDSU web site currently is indicating favorable weather for tan spot infection in many NDAWN

locations. Both sites are currently indicating a high risk of Fusarium head blight for winter wheat that currently may be flowering, especially in the south central and south east counties. In 2005, evaluations of winter wheat cultivars at Lisbon, ND indicated that CDC Falcon, Jagalene, McClintock, Wendy and Wesley had the highest FHB severities.

IPM SURVEY FINDINGS, May 25-June 5

NDSU IPM field scouts surveyed 98 wheat and 27 barley fields from May 25-June 1. For wheat, the predominate disease observed was tan spot, found in about 64% of the fields, and found in all crop reporting districts. Average severity of tan spot in symptomatic fields was 7.5%, but the range of severity was up to 37% in 4 winter wheat fields surveyed. No new leaf rust observations were made during the last week of May, but Jaycie Klabunde, field scout for the southeast and east central regions, found a very low level of leaf rust in southern Barnes county on June 5th.

Grain aphids were found only in very low numbers and only in east central counties surveyed. Of the barley fields surveyed, only 22% showed some fungal leaf spotting, and severities were low.

Marcia McMullen
Extension Plant Pathologist
marcia.mcmullen@ndsu.edu

SCLEROTINIA RISK MAP FOR CANOLA TO OPERATE IN 2007

The Sclerotinia risk map service for canola will begin June 14 and be active through mid July. Maps will be available twice weekly at the NDAWN and Northern Canola Growers Association websites at:

Sclerotinia is caused by the fungus Sclerotinia sclerotiorum. The fungus survives in the soil as hard black structures called sclerotia, which, when adequate moisture is present produce fruiting structures (apothecia) that release airborne spores. Although the fungus can produce spores throughout the season, canola is only at risk of infection during flowering.

The risk map bases its prediction on the likelihood that apothecia will be formed. In addition to the risk map, a map of expected canola growth stages and a map of estimated soil moisture content are issued. These other maps can be helpful for interpreting the risk of individual fields. If the forecasted risk is high and your field is at the flowering stage, then the risk of disease occurring in your fields would also be high; but if the forecasted risk is high and your field is not in the flowering stage yet, the warning does not apply to your field. The three warnings issued immediately prior to the beginning of flowering stage in your field are the most important for you. More than one high-risk warning during this period increases the probability of disease and therefore the need for fungicide applications.

Fungicides registered for sclerotinia stem rot in Canola include Quadris, Endura, Topsin M, T-Methyl, Thiophanate-methyl, Ronilan, and Proline. For information on fungicide rates and timing consult the 2007 North Dakota Field Crop Fungicide Guide (PP-622) available at:

For information on Proline, which was registered after publication of the 2007 fungicide guide, consult the manufacturers label at:

Comments and suggestions concerning the Sclerotinia risk map are welcome and should be addressed to Dr. Luis del Rio at the NDSU department of plant pathology.

Sam Markell
Extension Plant Pathologist
Samuel.markell@ndsu.edu

Luis del Rio-Mendoza
Canola Pathologist
(701) 231-7073
luis.delrio-mendoza@ndsu.edu

DOWNY MILDEW ON SUNFLOWER

Recent rains have created a favorable environment for many diseases, including downy mildew of sunflower. Symptoms of systemic downy mildew infection include stunting and distorted growth. Yellowing leaves and chlorosis (yellowing) along leaf veins occur on the upper side of the leaf, and a white cottony growth may be produced on the underside of the leaves. When wet weather frequently occurs, secondary infection or local lesions are likely to be seen. When the mildew spores blow in the air and land on leaves they produce small, localized lesions which are chlorotic on the upper leaf surface and have white spores on the underside of the leaf. These local lesions do NOT produce a systemic infection, and are unlikely to result in any yield loss.

Yield losses due to downy mildew are generally minimal, as affected seedlings usually die and the remaining healthy plants compensate for the plant loss by developing larger heads.  However, if strips of plants are affected, the "compensatory" ability of neighboring plants is minimized. Generally, a yield loss is not noticed if mildew incidence is < 5%.

No foliar fungicides are registered for curative control of systemic downy mildew, so prevention of the disease is the best approach to control. To minimize downy mildew on susceptible hybrids, nearly all sunflower seed sold in the Northern Great Plains is currently treated with a mixture of fungicides, including Apron and Dynasty. While the downy mildew fungus has largely become tolerant of Apron, Dynasty is effective against the mildew fungus but the current rate will not offer total control.  Higher rates, forecast to be on the label in the future, possibly with a companion fungicide, may offer more complete control.

Sunflower downy mildew exists as many "races," and according to surveys and greenhouse studies done by USDA-ARS pathologist Tom Gulya, there are currently five races in the Northern Great Plains (ND, SD, MN). Genetic resistance to all known mildew races, coming from USDA inbreds released in 1985, has produced commercial hybrids which are totally immune both in greenhouse tests and in growers’ fields.

Once downy mildew occurs, the downy mildew pathogen persists in the soil for many years as dormant spores. Given the right weather conditions (soaking rains the week after planting), a susceptible hybrid planted on known-diseased ground may develop downy mildew up to five years after an initial infection. If you notice downy mildew in your fields this year, it is important to plant a resistant hybrid with a seed treatment when you rotate back to sunflowers.

Sam Markell
Extension Plant Pathologist
Samuel.markell@ndsu.edu

Tom Gulya
Sunflower Pathologist USDA-ARS
Thomas.Gulya@ARS.USDA.GOV