The discovery of potentially devastating Asian soybean rust in a dozen southern states since last fall requires no-tillers to be ready to protect their fields with fungicides. And if Asian rust does race across the country on the spring winds, the demand for custom applicators could make their timely services hard to come by.
Predictably, sales of new and used spray equipment jumped as farmers began getting ready to handle their own timely applications.
But having the equipment is only part of being prepared. Knowing how to use that equipment is also crucial.
Bob Klein, an agronomist at the University of Nebraska in North Platte, Neb., who has been studying spray applications since the 1970s, says he’s now most often asked how to effectively control Asian soybean rust.
So he offered attendees at the 13th annual National No-Tillage Conference advice about nozzles, spray pressure, boom height and more.
Klein points to a study at Virginia Polytechnic Institute and State University that showed the importance of matching the fungicide spray pressure, measured in pounds per square inch (psi), to the type pf nozzle being used. (See Chart 1.)
The results indicated a pattern of better disease control as spray pressure was increased until a 55 psi application was less effective than 40 psi.
With the increased pressure, Klein explains, “The particles get so small that they evaporate. One of the characteristics of the nozzle tested (TK-30) is that it has a large area on which to form particles…