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A golden harvest near Oakesdale.
Photo by Teresa Hodges

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FARMER'S TOOLBOX

Overcoming production challenges

Workshop focuses on using variety selection, proper chemicals for pests

April 2019
By Trista Crossley


Production challenges and options to overcoming them was the topic of the final session of the Agricultural Marketing and Management Organization’s 2019 winter schedule in February. Ryan Higginbotham from HighLine Grain Growers talked about disease pressure and how choosing the right variety can help address those issues, while James Zahand of James Zahand Consulting talked about herbicides and weed resistance.

Pick wisely
Higginbotham began his presentation by reviewing how certified seed is produced, typically a five-year process that begins when a variety is identified for release. The steps include:

• Identifying “seed-worthy” ground that has minimal weed issues and is one crop removed from wheat (to eliminate volunteers);

• Ensuring purity at planting by cleaning the seed truck, planting equipment, drills, etc.;

• Season-long monitoring to stay on top of weeds and spraying;

• Inspection by the Washington State Crop Improvement Association preharvest to check for contamination of weeds, including a zero-tolerance policy for jointed goat grass;

• Ensure purity at harvest by cleaning all equipment, both the harvesting equipment and the receiving facility;

• Grade a sample at harvest;

• Cleaning the seed to remove off material, such as weed seed, other grains, rocks, chaff, etc.; and
• Submitting a sample to the Washington State Department of Agriculture to verify the purity and germination of the seed.

Higginbotham then addressed the different diseases that plague Pacific Northwest wheat crops and demonstrated how to use the variety selection tool at

smallgrains.wsu.edu to see how different varieties in different rainfall zones fare against these diseases.

Stripe rust. There are two types of varietal resistance: high temperature adult plant resistance and seedling or all-stage resistance. Seedling resistance is in effect all the time but is specific to a particular stripe rust race. Adult plant resistance is not stripe rust race specific, but it is temperature and growth stage dependent. In order to activate the adult plant resistance, temperatures need to be at least 70 degrees and plants have to be at a certain growth stage. When looking at which herbicide to use, growers should consider those with multiple active ingredients, because the more active ingredients, the longer the stripe rust protection will last. However, some herbicides have harvest restrictions or plant stage restrictions. This information is noted on herbicide labels.

Cephalosporin stripe. Higginbotham said this disease is more problematic in higher rainfall areas, and it favors soils with a low pH. Spores enter through root injuries often caused by freeze-thaw cycles and can overwinter on stubble. Seed treatment and foliage fungicides are generally not very effective. Delayed seeding dates can help because plants have a smaller root system, so there’s less damage caused by that freeze-thaw cycle. Tillage may help combat the disease, but won’t cure it. Resistant varieties are the best option.

Fusarium crown rot or dryland foot rot. This soil-borne disease infects wheat plants via the crown or roots and infects both winter and spring wheat. Any sort of drought stress predisposes plants to infection. Overfertilization can also promote infection. Higginbotham said crop rotation will help manage the disease, adding, “like anything else, if you go wheat on wheat on wheat, you are just asking for trouble.” Seed treatments will help as will appropriate seeding and fertility rates, but genetics are the best option.

Eyespot/strawbreaker foot rot. This disease causes distinct, eye-shaped lesions. The best way to manage for it is to plant a resistant variety. Growers should also avoid extremely early seeding and should apply a spring fungicide application to susceptible varieties prior to jointing. Seed treatment is not generally very effective.

Hessian fly. This mostly affects spring wheat, but it can be found in winter wheat. The best option for growers is to plant a resistant variety. Higginbotham said Hessian fly can be hard to treat in the Pacific Northwest because the region can have multiple hatchings. Other management ideas include crop rotation, some tillage and seed treatments. He added that the bugs can overwinter in residue and for growers not to count on an insecticide to help.

Higginbotham also touched on low falling numbers, canola and the pros and cons of seed treatments, as well as the benefits of fall-planted peas as a rotation crop for wheat.

“Growers should recognize that there are a litany of things that cause problems in wheat, and most of them we have solutions for, whether it’s a resistant variety, some sort of cultural practice or a chemical practice, there’s a way we can deal with those,” Higginbotham said afterwards. “But if you don’t know what it is or don’t identify it, you can’t tackle it.”

From disease to weeds
If nationally certified crop adviser James Zahand had a motto for his presentation, it would have to be “things are always changing,” specifically how weeds are adapting to the chemistries and practices that growers are using to try to control them.

“Once you identify the weed, then you have to think about the tools you have,” he told the group. “We’ve been using chemistry for decades, and because of the way we’ve used herbicides, weeds have developed resistance.”

Zahand told growers that knowledge is the key to slowing weed resistance. Growers should learn to identify what weeds they have, understand the tools they have to control those weeds and utilize a variety of cultural, physical and chemical tools to control those weeds.

Herbicides work by interfering with one or more vital plant functions such as:

• Photosynthesis (making food);

• Pigments (energy/light capture);

• Respiration (energy);

• Amino acids (protein/growth);

• Lipids (cell membranes); and/or

• Hormones (growth/reproduction).

There are approximately 30 different groups of herbicides based on mode and site of action, and Zahand warned growers that no new modes of action have been discovered since the early 1990s. He then walked growers through how the different modes of actions work and what symptoms plants will exhibit. He summarized his presentation by saying:

• Knowing the weed you want to manage will help you develop a plan of action;

• Understanding how herbicides are classified will help you understand how they work;

• Understanding how herbicides work will help you make better choices when choosing a herbicide;

• Choosing the right herbicide will give you better weed control and higher yields, hopefully at a lower cost; and

• Choosing the right herbicide will help manage herbicide resistance.

“Herbicide resistance is a serious issue,” he said. “We have a limited number of tools now, and there isn’t a lot more coming down the pike. Understanding the problems, the tools that growers have available to them, including tillage, will be important in slowing herbicide resistant now and in the future.”