Scab

Researchers from Kansas State University, Ohio State University and the University of Arkansas talked with Forrest Laws of Farm Press Publications on February 3, 2014, about Fusarium head blight in their respective wheat-producing regions.

Watch for the Dangers of Scab

When driving down a country road on a bright afternoon and gazing out into a sea of rippling wheat, one might be deceived by the picturesque front, not realizing how the individual grains within that field may start suffocating from an aggressive fungal disease: Fusarium head blight (FHB), also known as scab.

FHB can be detrimental to wheat, causing grain to have low test weights, lost yield, low germination and mycotoxin contamination.

FHB can display disease symptoms, as we discuss below. But it can also be present in a field, harming the crop and yield before symptoms are even visible and the disease can be identified.

When scab is visible in the crop, the primary symptom is the bleaching of some florets before they reach maturity.
This causes sterile flowers which produce kernels that have a shrunken, chalky, white appearance. This appearance has earned them the industry moniker of “tombstones.”

Symptoms of Fusarium graminearum on cereal grains
 


Symptoms of Fusarium graminearum on cereal grains



Fusarium KernelsThe Fusarium pathogen that causes scab isn’t unique to wheat. In fact, it causes disease in other crops, too, such as corn, and it can overwinter between crops among field stubble. This means that crop rotation practices often used to manage worm and insect pests aren’t effective when it comes to FHB.

For example, explained Jason Manz, cereals marketing manager, Bayer CropScience, if a field of corn is infected with Gibberella stalk rot, that same pathogen can overwinter and appear as scab the next year in wheat planted to the same field. Plant that field back to corn the following year, and the cycle continues.

The Disease Triangle

An added hurdle is that FHB thrives in the very same conditions that your crop needs to thrive: moisture, light and temperature.

“It contributes to what is known as the disease triangle,” said Randy Myers, product development manager, Bayer CropScience. “Three components — favorable weather, a host plant and presence of the pathogen — combine to create perfect conditions for disease development. It is in this situation that you need to be particularly diligent in preventing and managing scab.”

According to the U.S. Wheat and Barley Scab Initiative:
  • Scab-infected wheat is present worldwide wherever cereal crops are produced.
  • In the U.S., 31 out of 40 states surveyed contained wheat-infected scab.
  • During U.S. scab epidemics, yield losses can exceed 50 percent and cost nearly $300 million of profit.
  • A particularly devastating scab epidemic in the 1990s caused some growers to burn their scab-rampant fields rather than harvest them in hopes of reducing the fungal disease down the road.

Too Much DON and You're Done

While scab can lead to yield loss and poor grain quality, the most devastating effect might be mycotoxin contamination, most notably deoxynivalenol (DON). Occasionally referred to as vomitoxin, DON is a particularly potent mycotoxin produced by the Fusarium head blight fungus.

Even the most seasoned wheat growers may be surprised by how little contamination it takes for wheat to be considered toxic — and potentially unsellable. In fact, one part per million (ppm), the maximum DON level allowed in grain produced specifically for human consumption, is equivalent to one penny out of $10,000 and one minute out of two years.

DON can pose a health risk if consumed in high amounts, so the Food and Drug Administration (FDA) has set guidelines for the maximum DON levels allowed in wheat products used for human consumption and livestock feed. Even trace amounts of DON can reduce flour quality for millers and may be unacceptable for malting and brewing. Harvested grain containing more than 5 percent of scab-infected kernels can contain enough toxin to be harmful to humans and animals.

DON-infected grain that is potentially toxic to humans and livestock is also difficult to market.  In 2013 the Chicago Board of Trade lowered the limits on the amount of DON in wheat that could be shipped to 3 parts per million, and the level can't exceed 2 ppm to avoid price discounts. 

Few visuals illustrate the effects of scab on grain quality as well as a side-by-side comparison. The two loaves of bread in this picture were baked using the exact same recipe, the same temperature and even the same ingredients — except for one. Flour made from scab-infected wheat was used in the top loaf, while the bottom loaf was baked with uncontaminated flour.

Loaves of Bread 

Maximizing Wheat Quality and Yield

The key to a strong start is building a clean foundation. A 2008 article published by North Dakota State University reinforced how seven responsible management practices are essential for preventing and defeating scab.

These management practices are:

  1. Crop rotation
  2. Resistance 
  3. Seed Treatment
  4. Tillage
  5. Planting
  6. Fungicides
  7. Harvest

The base starts at the planning stage: to rotate or to not rotate. Because the Fusarium pathogen overwinters in the residue from corn or wheat crops, the recommended pathogen-reducing crop rotation is corn-soybeans-wheat, because winds can carry scab from one neighboring field to another. Even if you make preparations to thwart scab, it would still be wise to prepare for a potential infection.

When considering tillage practices, procedures that bury residue from small grains and corn reduce the potential of scab since fungus survives and thrives at or above soil surface. Planting must be given especially careful consideration. Since the most favorable conditions for scab proliferation occur during prolonged periods (48 to 72 hours) of high humidity and warm temperatures (75 to 85 F), staggered planting is recommended to reduce risk of an entire crop flowering during a favorable infection period.

When evaluating fungicides as part of your practice to manage or prevent FHB, it is important to note that not all fungicides are created equal.

Strobilurins:  Use Caution

Among wheat growers, it is not uncommon to assume that strobilurin chemistries, which are very effective at controlling foliar disease, will be just as effective against scab. That is not the case, and poorly timed strobilurin application can, in fact, do more harm to your crop than good.   

“Growers who use strobilurin chemistries face an even greater risk because the formula does not contain any active ingredients for countering scab,” Myers explained. “In fact, strobilurins applied after the flag leaf growth stage may actually initiate increased DON levels.”

Yet an answer is available. To prevent scab and dangerous levels of DON from cropping up and draining your grain, university Extension agents highly recommend using Prosaro fungicide along with responsible management practices, due to its impressive track record:

The Power of Prosaro

  • As the leading fungicide for fighting scab in the U.S., Prosaro has been rigorously tested on the performance of its two active ingredients
  • North Dakota State University rates the triazole chemistry in Prosaro as “very good” — the highest among fungicides in efficacy against scab*. 
  • Along with being the top product in the U.S. for combatting scab, Prosaro is also the standard scab fungicide used in government-approved European countries

"To take on DON, steer clear of strobilurin chemistry at flag leaf emergence and later, and apply Prosaro at early flowering,” Myers said. “If you want to grow high quality wheat, plan to treat your crop around Feekes 10.51 to get the best control of leaf and head diseases, and preserve both yield and quality."

Prosaro Frequently Asked Questions 
Results of replicated field trials illustrate how Prosaro can improve wheat quality and help achieve more of the crop’s yield potential.

Grower satisfaction overwhelmingly supports the data. In a recent survey, Prosaro users were asked to provide candid feedback about their experiences with Prosaro. All of the unfiltered reviews and ratings can be viewed online here.

According to wheat grower Rob Richardson of Vicksburg, Mich., “A few years ago, we actually had a field that didn’t get put into the Prosaro program, and that field yielded less than half of what our normal overall farm yield was for that year.”

Greg Messer, a grower in Richardton, N.D., says he’s been using Prosaro for four seasons because its broad-spectrum disease control has helped him maximize yields and profit potential. “When you apply Prosaro in one row and not the other, you can see immediately see the difference when you run a yield monitor against it,” he said. “You can actually see the difference from a mile away, just in the color of the straw.”

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Source: Roger Abbott – AllAboutFeed.net

A shocking 99% of all grain samples collected by Alltech during their summer harvest survey contained mycotoxins. 83% of all samples contained multiple mycotoxins. Action of feed manufacturers is absolutely necessary.

Producers and feed manufacturers have been urged to take steps to manage the storage of their feed ingredients more carefully this year to limit mold growth and combat the annual international mycotoxin levels challenge.

 » more
Source: U.S. Wheat & Barley Scab Initiative

Upper Midwest wheat breeders continue to be sharply focused on Fusarium Head Blight (FHB) or scab, a disease that has caused billions of dollars in damages to U.S. wheat and barley crops since the early 1990s. Serious scab infections result in lower yields and test weights and also often trigger formation of a primary mycotoxin known as DON (short for deoxynivalenol).

Fortunately, wheat breeders in Minnesota, North Dakota and South Dakota have made substantial strides in developing varieties with moderate resistance to scab.

 » more
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