Wheat Diseases, Starter Fertilizer, and Rattlesnakes in One Afternoon
Watch Out For Rattlers
There’s a slight difference between your typical field day and the one held each year in late June at the Dakota Lakes Research Farm near Pierre, South Dakota.
“Look out for rattlesnakes,” good-naturedly warned Dwayne Beck, farm manager, to the farmers and agribusiness officials going through tests plots led by scientists like Emmanuel Byamukama, South Dakota State University Extension plant pathologist. “They’re as scared of you as you are of them.
“The only difference is they have fangs, you
Look Out For Wheat Diseases
Fortunately, rattlesnakes leave wheat alone. Disease doesn’t.
Byamukama says knowing where a disease infects plants can influence treatment options.
Know Where Disease Infests Wheat
For example, if diseases infest roots, should you apply a fungicide? No, because it infects the roots. However, a foliar fungicide can curb a disease like fusarium head blight (scab) that is carried by wind-borne pathogens that infect the head, says Byamukama.
Scab Spraying Guidelines
Weather greatly influences whether a scab outbreak occurs. Seventy-five to eighty-five degree temperatures combined with periods of rainfall and high humidity can favor infections. A wheat field that’s 15% flowered is when a treatment should be considered with a triazole fungicide like Prosaro or Caramba. Don’t treat with a strobilurin fungicide, as that can boost vomitoxin levels, says Byamukama.
Apply Fungicides Judiciously
Apply fungicides only when necessary, says Byamukama. “Scout for diseases,” he says. “If conditions are not threatening, don’t spray and save money. If there is no disease, you can also select for (fungal) resistance.”
Unnecessary applications in the absence of diseases can also select for resistant fungi that spurn fungicides. Other disease-management options for diseases like scab include resistant varieties, he says.
Starter fertilizer is tailor-made for cold and rainy springs like this one, notes Ron Gelderman, SDSU Extension soils specialist. “Two-thirds of the time, we see a starter response, but just 30% of the time there is a yield response,” he says. “And if conditions are good in South Dakota, there is not much response to starter fertilizer.”
Sulfur Deficiencies Sap Corn
Sulfur deficiencies are becoming more common in some South Dakota corn fields, says Gelderman. The good news is corn can snap out of it on high organic matter soils, he says. Sandy low-organic matter soils can benefit from sulfur applications, he notes.
War in the Wheat Field
A ripening wheat field is one of the most peaceful sights on the South Dakota prairie this time of year.
If you take a sweep net, though, like Pierre, South Dakota, farmer Mark Weinheimer, is doing, you’ll discover a war going on. Predator insects are constantly devouring wheat pests like aphids.
Let Predators Win
Over time, these good guy insects can pay big dividends, says Ada Szczepaniec, SDSU Extension entomologist (center, blue shirt). That’s why it’s a good idea to let predators do their work and spray insecticides only when predator insects fail to control pests, she says. In the case of the English grain aphid, insecticide treatment is recommended when numbers tally 10 per wheat head, she says.
Spare the Beneficials
“Even though there are lots of insecticides on the market, there are just a few classes like organophosphates and pyrethroids,” she says. “So if we keep using them over and over again when they are not needed, insects can become resistant to them. Also, we kill beneficial insects with them.”
Starter Fertilizer, sulfur deficiencies, predator insects