WATERLOO, NY — Spraying soybeans isn’t just about effective pest and disease control. Best management practices (BMPs) also include keeping spray where it belongs. Bob DeWaine, technology development representative for Monsanto, presented “Back to the BMPs of Spraying: Getting Ready for Dicamba Resistant Soybeans” at the recent Soybean Small Grains Congress 2017, hosted by Cornell Cooperative Extension Northwest New York Dairy, Livestock & Field Crops Team.
“You have to scout fields to know what you’re spraying for,” DeWaine said.
You’ll likely need more than one herbicide.
“The days where you think you need only one herbicide are over,” DeWaine said. “We need multiple modes of action.”
By carefully selecting products to target issues, you can better ensure that you’re spending wisely.
How you apply spray makes a big difference in efficacy.
“Look at many herbicide labels,” DeWaine said. “The size of the weed determines the amount you use. As the saying goes, ‘Dead weeds don’t produce seeds.’ You have got to kill them.”
Application can also affect neighbor relations. Physical drift refers to physical movement of spray particles during spray application.
“Whatever herbicide you use, follow the label and you won’t have drift issues,” DeWaine said.
He noted that many crops grown in New York are sensitive to herbicides, such as grapes.
For Monsanto’s Roundup Ready Xtend, for example, producers must leave a downwind buffer between the last treated row and the closest downwind edge of 110 feet when applying 22 fluid ounces per acre and 220 feet when applying 44 fluid ounces. The more heavily an area is sprayed, the greater size the buffer should be.
“If you are spraying early, a non-planted or emergent field can be a buffer,” DeWaine said. “Be a good neighbor and find out what they want to grow.”
A buffer zone may also include roads, farm lanes, barns or other structures.
To keep spray of any produce where it belongs, follow mixing directions (if mixing is required) and use the recommended application equipment and methods. For example, if rain is expected, some products recommend waiting so it doesn’t wash off plants. The wrong nozzle may distribute smaller droplets, which are more prone to blowing where they don’t belong.
DeWaine compared large droplets to basketballs and small ones to ping pong balls. In a breeze, the basketballs will likely fall directly where they belong, unlike ping pong balls.
Herbicide volatility refers to the movement of a herbicide as a gas or vapor after spray application. Pay attention to wind speed.
“Don’t spray if the wind speed is greater than 15 miles per hour,” DeWaine said.
Humidity can also affect spraying time, as low humidity or temperatures above 91 degrees can cause larger droplets to form.
DeWaine cautioned against mixing herbicides unless expressly permitted by the manufacturers’ labels.
Once spraying, producers must stay at 15 miles per hour or slower to ensure better coverage and increase the accuracy of spraying. Setting the boom height at the lowest effective height over the target pets or crop canopy, based on the manufacturer’s directions also helps ensure less drift.
Sprayer contamination presents another issue. Most operations use just one sprayer for multiple purposes. If you use the sprayer on different plants without cleaning it according to the product label, you may damage other crops. Ideally, clean the sprayer immediately after use. Many herbicides require a triple rinse procedure with a commercial detergent, sprayer cleaner or ammonia.
“After spraying, scout fields to detect weed escapes or shifts in weed species,” DeWaine said.
That way, you can shift your spray strategy to a more effective product as needed.