ISSUE 2   May 20, 2010

EARLY SEASON TAN SPOT MANAGEMENT WITH FUNGICIDES

A number of fungicides are available for control of early season leaf spot diseases in wheat. The following table indicates products available and early season use rate.

Product

Active ingredient

Early season rate/A

Tilt, Bumper, Propimax, Propiconazole E-AG

Propiconazole

2 fl oz

Stratego

Propiconazole + Trifloxystrobin

4-5 fl oz

Quadris (after jointing)

Azoxystrobin

6.2 fl oz

Headline

Pyraclostrobin

3 fl oz

Quilt

Propiconazole + Azoxystrobin

7 fl oz

Penncozeb, Manzate, Dithane

Mancozeb

1-1.5 lb

All of the products have good activity against leaf spot diseases at the 3-5 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 greatest economic response from early season fungicide use occurs with:

* susceptible cultivar planted

* wheat planted into wheat ground

* rainy weather during early leaf stages

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

Application of fungicides with herbicides + other ingredients: Early season fungicides are successfully applied with most herbicides, as long as temperatures don’t get too hot or too cold right after application. However, addition of other ingredients has not been tested, and there is a risk of having too many ingredients interacting or inhibiting the other’s activity. We do not recommend adding any fertilizer ingredient with the early season fungicide/herbicide combinations (see Dave Franzen’ article on "Application of slow-release N products with herbicides/fungicides ins small grains" in the Soils section of this week’s Crop and Pest Report).

EASY SIGN-UP TO RECEIVE TEXT MESSAGE OR EMAIL ALERTS ON FUSARIUM HEAD BLIGHT (SCAB) RISK

Growers, ag consultants and others interested in the potential for Fusarium head blight (scab) risk during the growing season may now sign-up for alerts on the risk of this disease in their state or region. Individuals may sign up to have an alert delivered through a text message to their cell phone, or as an e-mail message.

The URL link for the subscription page is:

http://scabusa.org/fhb_alert.php

At this site, users can choose to subscribe to a text message or an e-mail alert, and can also choose to get message alerts from all states or just from the Northern Great Plains states. Most people will just want a regional alert. The Northern Great Plains alert messages will be from ND, MN and SD.

These alerts have been made possible through a collaborative effort of the US Wheat and Barley Scab Initiative and the national FHB (scab) Prediction Center which operates the FHB forecasting model.

I hope many of you will sign-up. It is a very easy system to use. I will be posting messages periodically to the site, and messages will be more frequent as we get closer to the flowering period of our northern crops.

 

SCABSMART WEBSITE

A website devoted to providing growers with management information for Fusarium head blight (scab) was initiated last fall. Information on variety response, fungicides, rotations, crop rotations and other management practices is provided for each grain class across the US. The website url is:

http://www.scabsmart.org/

For growers in our region, they can access information on hard red winter wheat, hard red spring wheat, durum wheat and spring barley. The site was developed with support of the US Wheat and Barley Scab Initiative and by collaboration of breeders, agronomists and plant pathologists across the US.

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

 

SUGARBEET – LOOKOUT FOR DISEASES

Rhizoctonia root and crown rot is caused by the fungus Rhizoctonia solani. The fungus causes infection when soil moisture range from somewhat dry to wet and soil temperatures at and above 65ºF. Characteristic symptoms of Rhizoctonia include sudden wilting of leaves, and petioles of outer leaves are blackened at the point of attachment to the crown. Initially, Rhizoctonia root and crown rot may kill plants in small areas in a field – sometimes a few acres. Over time, especially when rotating with susceptible hosts such as beans and corn, the pathogen population builds up and may damage entire fields. Fields with a history of severe Rhizoctonia root and crown rot should be planted with tolerant varieties. The fungicides Quadris and Proline provide effective control when applied before infection takes place. In growth chamber studies, infection take place at 65ºF and higher. Fungicides should be applied before the soil temperature at the 4 inch depth reaches 65ºF.

Sugarbeet plants that are in warm, wet soils may be affected by Aphanomyces root rot caused by Aphanomyces cochlioides. Optimum condition for infection occurs in wet soils at air temperatures of 72 to 82ºF. Aphanomyces can be devastating in the seedling stage, and can also cause serious root rot later in the season. Infected plants turn a sickly yellow green and tend to wilt in the afternoons of hot and sunny days. Fields should be assessed for the disease on hot sunny days since it would be easy to identify infected plants. Aphanomyces may infect a few plants to entire fields. Some plants may die; those that survive have their roots easily dislodged at harvesting. Plants that survive infection have reduced root yield, lower sucrose content, and higher impurities. Diseased roots have higher respiration rates compared to healthy roots. As a result, the quality of storage piles can be reduced significantly when diseased roots are stored with healthy roots. Aphanomyces can be managed by using tolerant varieties; using Tachigaren pelleted seeds; planting early when possible; keeping the soil dry by cultivation and enhanced drainage; controlling weeds; and avoid spreading of contaminated soil from infected fields to disease free fields.

Wet soils and a temperature of 77ºF also favor the protozoan Polymyxa betae that transmits Beet Necrotic Yellow Vein Virus (BNYVV) that results in the disease ‘Rhizomania’. Characteristic symptoms of Rhizomania include translucent yellow-green leaves that may have longer stalks and narrower blades, and stunted taproots with proliferation of secondary roots giving a bearded appearance and hence its name Rhizomania – ‘crazy root’ or ‘root madness’. The best way to manage Rhizomania is to plant resistant varieties early in the season. Typical fluorescent yellows symptoms are observed later in the season – late July and August.

Mohamed Khan
Extension Sugarbeet Specialist
701-231-8596
Mohamed.khan@ndsu.edu


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