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Wheat Disease Update – April 20, 2017

Wheat is beginning to flower throughout Virginia, so it is time to make decisions about fungicide applications for both Fusarium head blight (FHB, also known as scab) and to protect the flag leaf as the grains begin to form. Currently, the risk for FHB is low in most parts of Virginia, even for susceptible varieties. The FHB Risk Assessment Tool can be found at http://www.wheatscab.psu.edu. Keep in mind that this is a prediction tool and it will not predict FHB outbreaks 100% of the time. A current screen shot of the website is shown below. Rains are expected over the weekend, but dry weather over the past several weeks has not favored spore production by the FHB fungus, so risk of FHB infection is expected to remain low for wheat that is flowering over the next week. However, now may still be the time to apply fungicides for foliar diseases including stripe rust, powdery mildew, and leaf blotch. The flag leaf must be protected during grain development to maximize yields. Again, due to the dry weather some areas have very little disease, and scouting is still recommended prior to making a fungicide application. However, there have been numerous reports throughout the region of outbreaks of stripe rust (especially on Shirley) and powdery mildew. Do NOT apply a strobilurin or fungicide pre-mix containing a strobilurin after flag leaf emergence (Feekes 9) since this can increase DON contamination in the grain. Prosaro, Caramba, and Proline are the most effective products for reducing scab and DON contamination, and these fungicides will also control foliar diseases such as leaf blotch, stripe and leaf rust, and powdery mildew. A fungicide efficacy table for wheat can be found in a previous post.

Screen shots from the Fusarium Head Blight Risk Assessment Tool (http://www.wheatscab.psu.edu) on April 20, 2017. Currently, risk of FHB infection in wheat that is flowering is low in most parts of Virginia. The exception is along the Eastern Shore where conditions are typically more humid and favorable for spore production by the FHB fungus. For susceptible varieties such as Shirley, FHB risk is moderate to high in some areas. However, for moderately resistant varieties such as Hilliard, the risk is currently low. This illustrates the importance of variety selection in management of FHB and DON contamination in wheat.  

Wheat Disease Identification Guide

Copies of a Wheat Disease Identification Guide from Kansas State are now available and can be requested from Dr. Hillary Mehl at the Tidewater AREC (hlmehl@vt.edu). A PDF version of the guide can be downloaded here. Though not specific to Virginia, many of the diseases included in the guide occur in our region and detailed descriptions of symptoms and management recommendations are included. As always, if confirmation of a disease is needed for wheat or other agronomic crops, plant samples can be submitted to the Virginia Tech Tidewater AREC (6321 Holland Rd. Suffolk, VA 23437). When submitting samples, be sure to fill out the Plant Disease Diagnostic Form with as much information as possible as this will assist us with an accurate diagnosis. The form can be downloaded here: Plant Disease Diagnostic Form

Wheat Disease Update – April 11, 2017

Though it is still a little early to be making scab fungicide applications, it is time to start thinking about if and when to apply a fungicide to the wheat crop. Wheat in parts of Virginia is starting to head, but much of the crop is still at or close to flag leaf emergence. Stripe rust was observed this week in Warsaw, VA and has been confirmed on the Eastern Shore of Virginia and in southeastern Delaware. Stripe rust is likely widespread in the state, and susceptible varieties such as Shirley should be scouted for this disease. Stripe rust can spread very rapidly and a preventative fungicide may be needed to protect the wheat crop. More information on stripe rust and other wheat diseases can be found in a previous post. Wheat that is beginning to head this week will start flowering in a week or two. Currently, Fusarium Head Blight (FHB) risk is low in most parts of the state with a few moderate to high risk areas along the Eastern Shore. As the wheat crop starts to flower, it is important to monitor the FHB risk and apply fungicides as needed. Updates on FHB risk and management recommendations will be provided here and from the FHB Alert system throughout the period of flowering for the Virginia wheat crop. You can sign up for FHB text message and/or email alerts here. Also be sure to check the FHB Risk Tool (http://www.wheatscab.psu.edu/) as the wheat crop starts to flower. If FHB risk is moderate to high, an application of a fungicide (e.g. Prosaro, Caramba) may be needed to protect the crop from scab and DON contamination. An update fungicide efficacy table for wheat can be downloaded here:

NCERA 184 Wheat fungicide table 2017_Final

Section 18 authorized for Transform WG for control of sugarcane aphid on sorghum in Virginia

In accordance with Section 18 of the Federal Insecticide, Fungicide, and Rodenticide Act, the EPA has authorized the Emergency Exemption use of Transform WG (active ingredient = sulfoxaflor) to be used on sorghum to control sugarcane aphid (Melanaphis sacchari) in specified Virginia counties. The authorization will expire November 30, 2017. Foliar applications may be made at 0.75-1.5 oz/acre, with a maximum of 2 applications per acre per year. Please refer to the product’s Section 18 registration for further information, including application directions (at the time of this writing, the 2016 version of the Section 18 is the one available on cdms.net [the 2016 version expires on April 8]). Micah Raub and others with the Virginia Department of Agriculture and Consumer Services are acknowledged for their assistance.

Stripe Rust Confirmed in Wheat on the Eastern Shore of Virginia

On Friday, stripe rust was confirmed on a wheat sample from a field in Northampton County, Virginia. Steve Rideout, Extension Plant Pathologist at the Eastern Shore AREC, reported that infection is fairly severe and rainy conditions will favor the pathogen’s development.  This is an early sighting for this disease and constitutes a serious threat to our wheat crop. The disease was found on Shirley, which based on observations in previous years in known to be highly susceptible to stripe rut. A previous post with management recommendations including variety susceptibility ratings and a fungicide efficacy table for stripe rust and other wheat diseases can be found here:

http://blogs.ext.vt.edu/ag-pest-advisory/stripe-rust-found-in-north-carolina-wheat/

You should be scouting your wheat crop at this time, and if stripe rust is found on a susceptible variety, a fungicide application is recommended. If you have any questions or need assistance identifying diseases on your wheat crop, contact Dr. Hillary Mehl at the Tidewater AREC (hlmehl@vt.edu).

New Mid-Atlantic Soybean Disease Scouting Guide Available

A Mid-Atlantic Soybean Disease Scouting Guide was recently developed by Extension Plant Pathologists from Virginia Tech and the University of Delaware in cooperation with the state Soybean Boards and the Soybean Checkoff. An online version of the guide can be found here:

Mid-Atlantic Soybean Disease Scouting Guide

Hard copies of the guide are available at the Virginia Tech Tidewater AREC, and requests for guides can be sent to Dr. Hillary Mehl (hlmehl@vt.edu). These will also be available at grower meetings and field days in 2017.

Stripe Rust Found in North Carolina Wheat

This week, stripe rust was found in Robeson County, NC. The disease was observed in wheat variety SS 8404 which is susceptible to stripe rust. Current weather conditions (cool, wet) are generally favorable for spread and development of stripe rust, and it will likely move north into Virginia before the end of the wheat growing season. However, stripe rust is typically a problem only in susceptible varieties. With this in mind, it is important for growers to determine which of their planted varieties are susceptible to stripe rust so they will be prepared to scout and apply a fungicide once the disease makes its way to Virginia. One popular variety, Shirley, is very susceptible to stripe rust, and outbreaks of this disease were observed in some fields planted to Shirley in 2016. Stripe rust and other disease ratings for wheat in Virginia can be found in the link below for the VCE Publication Small Grains in 2016. A link to the Diseases in Small Grains chapter from the 2017 Pest Management Guide for Field Crops is also attached. This includes management recommendations and a fungicide efficacy table for stripe rusts and other diseases of wheat.  Several different fungicides are available that are rated “Excellent” for stripe rust control, but fungicides are most effective when applied prior to disease development. Thus, if you know you have a variety is that is susceptible to stripe rust you should be scouting those fields and apply a fungicide if stripe rust is observed. There is no need to spray wheat for stripe rust at this time, but it is important to be aware and be prepared. If you suspect you have stripe rust, you can send a photo and/or sample to Dr. Hillary Mehl at the Tidewater AREC (hlmehl@vt.edu).

Small Grains in 2016 (variety disease susceptibility ratings)

PMG2017: Small Grains Disease

 

 

EPA review of pyrethroids

The EPA is in the process of reviewing some of our older, broad-spectrum classes of insecticides. The comment period is now open for the preliminary ecological risk assessment of pyrethroids. I strongly support the need for continued availability of these materials because they are relatively safe for mammals and biodegradable. Importantly, pyrethroids are the only option for pest control of certain insect pests in some cropping systems. Entomologists, including myself, at universities throughout the Southeast have expressed their support for pyrethroids in a letter to the EPA. However, the EPA is really looking to hear from people that use these products responsibly. The below link provides a tool to make comments on EPA dockets without looking up each product individually. It also includes the type of information that is most helpful and a template to follow if so desired. Comments from our Virginia growers will be much appreciated!

https://www.votervoice.net/PWG/campaigns/48706/respond

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Virginia Eastern Shore Ag Conference and Trade Show

Join us in Melfa, VA for the 27th Annual Eastern Shore Agricultural Conference and Trade Show on January 25-26, 2017. This event is free, open to the public, and will be held at the Eastern Shore Community College Workforce Development Center. We will offer Virginia Pesticide Recertification credits for categories 1A, 10, 60, and 90. We will also offer Certified Crop Adviser Credits for nutrient management (2), soil and water (1), integrated pest management (4.5), crop management (6), and professional development (0.5). Click on the following link for topic areas being presented: ag-conf-press-release-2017