Category Archives: Crop Update

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 ( 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

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:

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 (

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 (

Small Grains in 2016 (variety disease susceptibility ratings)

PMG2017: Small Grains Disease



View the Program: Virginia Eastern Shore Ag Conference and Trade Show

We look forward to seeing you January 25th and 26th at the 27th Annual Eastern Shore Ag conference & Trade Show! You can find the program online at: Virginia pesticide re-certification and Certified Crop Adviser credits will be available. See the program for more information.

The event will be held at the Eastern Shore Community College Workforce Development Center, 29300 Lankford Highway, Melfa, VA 23410. When you enter the driveway to the Community College, we will be meeting in the building to the left.

The Annual Oyster Roast will be held on Wednesday night, January 25th beginning with a social at 6:00 pm and oysters served at 6:30 pm. Along with oysters, there will be all-you-can-eat barbecue, sides and beverages. Tickets will be $35.00 in advance and $40.00 if purchased the day of the oyster roast.

If you have any questions or concerns please contact either Theresa Pittman ( or Ursula Deitch ( for accommodation. Thank you!

Registration is open for the Mid-Atlantic Crop Management School.


November 15-17, 2016
Princess Royale Hotel in Ocean City, MD

Registration is open for the 22nd annual Mid-Atlantic Crop Management School. This year’s school will feature 2 ½ days of timely presentations in the areas of crop management, nutrient management, pest management, soil and water management, and climate. This year, the school will also feature the popular Crop School on Wheels field tour (limited to 50 participants). Nutrient management (VA, MD, DE, PA), pesticide, and certified crop adviser (CCA) credits will be available. Register early for the best selection of sessions.

The session schedule is online at:

Registration information is posted at:

Contact Amy Shober ( or Jarrod Miller ( with questions about the school. We look forward to seeing you there.

The Mid-Atlantic Crop Management School is organized by Extension Specialists from Virginia, West Virginia, Delaware, and Maryland featuring speakers from across the nation.


Late blight was found in Accomack County, VA yesterday on potato. Growers on the Eastern Shore and other areas of the Commonwealth should scout their fields and take preventative measures. Please let us know if you have any questions. For more information on this potentially devastating disease of potato and tomato visit:


Wheat Disease Update – April 12, 2016

Stripe rust has been found on wheat in southeastern Virginia (Suffolk) and the Eastern Shore (Northampton County). Stripe rust is not observed every year, but it can be more aggressive than leaf rust and spread very quickly if temperatures are moderately warm and humidity/rainfall is high. Many wheat varieties are susceptible, and we do not have good stripe rust ratings for the region because the disease is fairly rare. Pictures showing typical symptoms of leaf rust and stripe rust are below. Fields should be scouted, and keep in mind it is more important to catch stripe rust early than leaf rust. If a field has good yield potential and stripe rust is present, a fungicide application is recommended. In addition to rust, powdery mildew has been reported from throughout Virginia and leaf blotch has been observed in southeastern Virginia, so as the wheat crop approaches the flag leaf emergence growth stage, it is time to start thinking about disease management. For specific fungicide recommendations, see my earlier post (April 7, 2016).

Stripe Rust

Leaf Rust

Leaf Rust

Wheat Disease Update April 7, 2016

As the wheat crop approaches the flag leaf emergence growth stage, it is time to start thinking about disease management. When conditions are conducive to disease development (e.g. high humidity, warm temperatures) foliar fungicide applications may be necessary to protect wheat yield and quality. The mild winter in 2014/2015 resulted in early onset of foliar diseases in some areas, and powdery mildew and rust were reported from a few fields as early as December. Recently, powdery mildew has been reported from throughout Virginia, leaf blotch has been observed in southeastern Virginia, and leaf and stripe rust have been reported just south of Virginia in North Carolina.

Wheat Powdery Mildew

Wheat Powdery Mildew

Once the flag leaf emerges, this leaf surface, which feeds the developing grain, should be protected from disease if symptoms are observed on the lower leaves and conditions are conducive to disease development. Fungicides containing a strobilurin should not be applied after heading but are a good option for control of foliar diseases as the flag leaf emerges. Late applications of strobilurins can increase DON (vomitoxin) if scab infections occur during flowering. Triazoles including Caramba, Proline, and Prosaro are good options for scab control and will also control late-season foliar disease. Currently, scab risk in the region is low but growers should consult the FHB prediction tool ( as the crop gets closer to flowering. Ideally, fungicide applications should be made based on scouting and/or risk of infection and disease development due to weather conditions. A fungicide efficacy table for many of the products registered for wheat can be found below.

2016 Wheat Fungicide Efficacy Table

As always, for more information on disease management in field crops feel free to contact Dr. Hillary Mehl, Extension Plant Pathologist by email ( or phone (757-657-6450 ext. 423).

Bt-Corn Refuge Requirements for Virginia Counties With and Without Cotton Acreage

Field corn hybrids—what are you buying? The dizzying array of Bt trait combinations available in field corn hybrids makes it important to understand what you are buying in a corn hybrid. Because of the different Bt toxins expressed in the plants, different hybrids protect, or not, against different insect pests.  So you should choose your hybrids at least in part based on the history of insect pest pressure in your fields. Good summaries of which hybrids protect against which insect pests are provided in the fact sheets, below (developed by Dr. Chris Difonzo at Michigan State University).

What are Bt-corn refuges and why do we need them? Bt-corn refuges are areas within or near Bt-hybrid planted fields where non-Bt hybrids are planted. They can be either structured (planted as a block or series of rows), or as refuge-in-a-bag (RIB) where the seed is pre-mixed to the correct ratio of Bt and non-Bt hybrids. In Virginia, the refuge requirement is primarily because of the corn earworm. Having the non-Bt corn refuge available in the near vicinity of the Bt hybrids allows at least some corn earworms to not be exposed to the toxins—which should prevent or slow the resistance development process.

Refuge requirements for counties with no cotton! Non-Bt corn refuges are required for corn fields planted to Bt hybrids. These requirements (% of field that must be planted to a non-Bt hybrid or RIB) are different for the different Bt-corn hybrids—and these details are presented in the fact sheet, below, ‘Handy Bt Trait Table’.

Refuge requirements for counties with cotton! Bt-corn refuge requirements are different for areas where cotton is grown because the risk of corn earworm (also called cotton bollworm) developing resistance to the Bt toxins in these areas is greater. Corn earworm attacks both corn and cotton and some of the Bt traits in corn hybrids are also in cotton varieties.  Feeding on the same Bt products in both crops exposes corn earworm to the same toxin in successive generations in the same growing season (corn first, then cotton).  This increases the risk of the insects developing resistance to the toxins. For Virginia, EPA has designated Dinwiddie, Franklin City, Greensville, Isle of Wight, Northampton, Southampton, Suffolk City, Surry, and Sussex as cotton growing regions.  Refuge requirements for the different Bt-corn hybrids are presented in the fact sheet, below, ‘Handy Bt Trait Table for the Southern Cotton-growing Region’.

Abiding by Bt-corn refuge requirements is good stewardship and important for helping sustain the efficacy of Bt-corn hybrids against insect pests. So, to determine your Bt-corn refuge requirement, you need to know if you are planting in a cotton-growing county, and what varieties you plan to plant. Read the attached fact sheets carefully for details to help you select the right corn hybrids for your farm, and what your refuge requirements are.

HandyBtTraitTable2016 CottonRegionBtCornTraitTable2015


Herbicide-resistant Italian Ryegrass

With harvest in full swing, it is hard not to forget about weed control in wheat.  Primarily of concern is herbicide-resistant Italian ryegrass.  In the past, ACCase- (Hoelon) and ALS-inhibiting (PowerFlex and Osprey) herbicides provided control of this weed.  However, Italian ryegrass biotypes resistant to these products have developed, but that is not to say these herbicides will no longer work in your area.  For example, Osprey is still effective throughout most of Eastern North Carolina, but once you move into the Piedmont, ryegrass control by Osprey is hit or miss.  In areas with known ALS-resistant Italian ryegrass, Zidua is suggested delayed-preemergence.  Delayed-preemergence means 80% of germinated wheat seeds have a shoot at least ½-inch long.  If applied prior to this stage, injury may occur.  Zidua is a seedling-shoot inhibitor and will not control emerged weeds, therefore, it is important for fields to be clean prior to application.  Axiom applied spike (applied preemergence, Axiom can cause severe injury) also controls Italian ryegrass if a timely activating rainfall is received following application.  Another option on no-till or minimum-till fields (where stubble from previous crop has not been incorporated) is Valor SX applied preplant.  Valor must be applied at least 7 days prior to wheat planting and should be applied in combination with either paraquat or glyphosate to control emerged weeds.  Tillage should not be performed after Valor SX is applied.  Italian ryegrass control by Finesse is variable and growers should expect only suppression.  If Finesse is applied, plant only STS-soybean following wheat harvest.  Postemergence options for Italian ryegrass include Axial XL and Osprey.   Although most Italian ryegrass is Hoelon-resistant, Axial XL (also an ACCase-inhibiting herbicide) still seems to work in most areas.  Osprey may also control Italian ryegrass in areas yet to develop resistance and will also control small bluegrass.

Ryegrass in the non-treated control.

Ryegrass in the non-treated control.  Received glyphosate 14 days preplant.

Ryegrass control by Valor SX plus glyphosate applied 7 days preplant

Ryegrass control by Valor SX plus glyphosate applied 7 days preplant