ISSUE 3   May 24, 2007

WHEAT RUSTS DEVELOPING IN STATES TO OUR SOUTH

Jeff Stein, SDSU Plant Pathologist, reported on May 21 that he observed leaf rust in hard red winter wheat plots in Brookings. Incidence was high on the cultivar ‘Expedition’, but severity was low. Jeff did not see any stripe rust yet.

With the occurrence of leaf rust in SD and in more southern Plains states, the potential for the disease showing up in wheat in ND anytime soon is fairly high. NDSU IPM field scouts will begin looking for its occurrence this week and next. Winter wheat is progressing rapidly in the state, with Area Extension specialists reporting maybe only a week away from flag leaf stage. Winter wheat should be scouted closely as the crop approaches the flag leaf stage, for presence of leaf rust, as many cultivars are fairly susceptible.

The cooler, wet weather expected this week and over the Memorial weekend, also may favor some development of stripe rust. North Dakota’s experience with stripe rust is minimal, but this rust has resulted in rapid infection and yield loss in winter wheat in states to our south in recent years.

Leaf rust is characterized by oval or round, red pustules of spores breaking through the leaf epidermis, while stripe rust is characterized by pale orange to almost yellow longitudinal stripes of spores breaking through the epidermis. The following figure, provided by Pete Neal, shows both types of rust infections on the leaf surface, for comparison.

leaf rust and stripe rust
Leaf rust & stripe rust

 

TAN SPOT FAVORED BY RECENT RAINS

Recent rains will favor continued development of the fungus that causes tan spot infection in wheat. The causal fungus, Pyreonphora tritici-repentis, survives in wheat residue, and when conditions are wet and rainy, the fungus’s fruiting bodies on the straw swell and release spores that can infect the leaves. The early infections appear as small tan to brown spots with yellow halos (see figure of symptoms). NDSU Area Extension specialists are reporting observation of this disease across the state in some winter wheat and spring wheat fields where wheat residue is present.

tan spot symptoms
Early season tan spot symptoms

When tan spot is present and wheat crops are in the appropriate stage for early herbicide application, generally the 4-5 leaf stage, a fungicide often is applied or tank mixed with the herbicide application.

Some combinations of products may cause slight injury, so herbicide and fungicide labels should be checked before tank mixing. A spreader/sticker addition is NOT needed for the fungicide, if applied in combination with a herbicide. Early season fungicide use rates generally cost approximately $3.00 to $5.00/acre.

A number of fungicides are available for control of early season leaf spot diseases in wheat. These products generally are also registered for barley, if early net blotch or spot blotch should occur. The following table indicates products available and early season use rate.

Product

Active ingredient

Early season use rate

Tilt, Bumper, Propimax

Propiconazole

2 fl oz

Stratego

Propiconazole + Trifloxystrobin

4-5 fl oz

Quadris

Azoxystrobin

6.2 fl oz

Headline

Pyraclostrobin

3 fl oz

Quilt

Propiconazole + Azoxystrobin

7 fl oz

Penncozeb, Manzate, Dithane Manex II

Mancozeb

1-1/12 lb

All of the products have good activity against leaf spot diseases at the 4-5 leaf stage. The mancozebs are protectants and generally are less rain fast than the other products.

NDSU research trials with winter wheat and with tan spot susceptible spring wheats have shown yield responses generally in the range of 4-5 bushels in wet years, and some responses up to 8 bushels. Average yield response is around 3 bushels. The majority of these trials have been with wheat planted into various levels of wheat stubble. The greatest economic response from early season fungicide use is generally seen under the following conditions:

Producers who had wheat in a field two years ago may have enough remaining wheat stubble to see some tan spot infection.

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

 

SOYBEAN RUST FOUND IN LOUISIANA

Soybean rust was found May 8th in Iberia Parish, Louisiana. The disease was found on kudzu, a weed-host of the pathogen, and has not yet been identified on soybeans. This identification of the disease in Louisiana is 53 days earlier than the initial find last year. The associated press has written about this occurrence in a recent press release.

Although this is a significant development, it is too early to worry about soybean rust in North Dakota. Numerous factors would have to come together for soybean rust from Louisiana to threaten North Dakota. At this point, it is best to be aware of the disease, but wait to see what happens in the south.

Throughout the United States, sentinel plots and spore collectors are set up to track the movement of soybean rust. North Dakota is participating in the national soybean sentinel plot project with 20 soybean sentinel plots and ten legume sentinel plots. Additionally, two spore collectors will be stationed in Richland and Cass County. Monitoring of sentinel plots and spore collectors in North Dakota will begin in June.

For current information on the movement and identification of soybean rust the following links are available.

http://www.dtnsoybeanrustcenter.com/

http://www.usda.gov/soybeanrust/

If soybean rust develops in the south and begins to spread toward our region, we will keep people informed. Should soybean rust reach ND, numerous fungicides have received a Section 3 or Section 18 registration and can be used to control the disease. Information is available at:

http://www.ag.ndsu.nodak.edu/extplantpath/Soybean%20Rust/Soybean%20Rust.htm

http://www.ag.ndsu.edu/pubs/plantsci/pests/pp622/pp622.pdf

http://www.ag.ndsu.nodak.edu/aginfo/pesticid/pesticid.htm

http://www.agdepartment.com/Programs/Plant/Section18Exemptions.html

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

 

QUADRIS/WARRIOR WITH ZEON TECHNOLOGY TANK MIX APPROVED ON SUNFLOWER

A tank mix of Quadris fungicide and Warrior with Zeon Technology insecticide has received a Section 2(ee) registration on sunflower. Quadris flowable fungicide (Azoxystrobin; FRAC group 11) and Warrior (lambda-cyhalothrin) are both Syngenta products. Quadris can be applied at 6-15.5 fl oz/A for suppression of sunflower rust. Warrior can be applied various rates (1.28 – 3.84 fl oz/A) to suppress numerous sunflower insect pests including banded sunflower moth, sunflower moth, sunflower beetle, sunflower seed weevil, sunflower stem weevil, cutworms and grasshoppers.

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

Jan Knodel
Extension Entomologist
Janet.knodel@ndsu.edu

 

NDSU POTATO BLIGHTLINE TO OPERATE IN 2007

The Plant Pathology Department at North Dakota State University will again be providing the potato blightline service at no charge to the potato industry of North Dakota and western Minnesota in 2007. This will be the thirteenth year that this service has been provided and sponsored by Syngenta Crop Protection. The hotline uses local weather data collected from weather stations throughout our area to forecast the occurrence and spread of late blight in fourteen non-irrigated and nine irrigated production areas in ND and western MN. The data is processed by the North Dakota Agricultural Weather Network (NDAWN) and analyzed by a computer program (WISDOM) to forecast when conditions are favorable for late blight to occur.

The forecast information is used by plant pathologists Gary Secor and Neil Gudmestad to make late blight management and fungicide recommendations. The recommendations are made Monday, Wednesday and Friday of each week during the growing season. The first late blight hotline will be Friday June 1st, and the hotline will continue through mid September depending on disease pressure. The hotline will also be used to confirm late blight infection and serve as clearing house for national late blight information. In addition to late blight forecasting, the hotline also provides cumulative P-values for early blight disease forecasting and management recommendations. Finally, it serves to alert growers of other disease and insect news, as well as posting messages of general interest such as potato field day dates.

The hotline recommendations can be accessed by phone or website.

The toll free phone number is 888.482.7286

The NDAWN website for potato disease forecasting contains colored maps of ND to pictorially illustrate the late blight severity values (both two day and seasonal), favorable day values and P-day values for early blight throughout ND. That site is: www.ndawn.ndsu.nodak.edu  Go to applications and then click the drop down box for potatoes.

Growers and scouts are encouraged to send suspect late blight samples to us for positive identification. Late blight is a community disease and proper identification and prompt notification is important. Leaf samples should be placed in a slightly inflated zip-lock plastic bag without a wet towel and sent to:

Gary Secor
Plant Pathology
Walster Hall 306
North Dakota State University
Fargo, ND 58105.

Our phone number is 701.231.8362 and email address is gary.secor@ndsu.edu. We look forward to a successful potato year.


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