PREPARING SPRAY equipment for the anticipated battle with Asian soybean rust (ASR) in U.S. fields sounds a bit like strategizing for a military campaign. “Be sure you know about nozzles, pressure and volume and how to use fungicides. Then prepare your equipment and follow where the rust is located,” advises Palle Pedersen, Iowa State University agronomist. “It doesn't help to panic. We have the technology to manage this disease and we have prepared very well for it.” Pedersen recently returned from a trip to South America to investigate how that country's soybean producers deal with the disease they have been fighting since 2001. “Farmers in South America have learned to manage it and we can do the same thing,” Pedersen says.
Cover the canopy
John Deere researchers followed ASR back to Brazil for recent research trials measuring how nozzle type, pressure, speed, gallons per acre and other variables influence the effectiveness of fungicides. Mike Miller, John Deere product planner, says, “The biggest take-home message from our research in Brazil is that preparing for Asian soybean rust does not necessarily require a tremendous amount of changes to equipment. There are a lot of sprayers out there on the marketplace that, with a few modifications in setup, can be equipped to properly apply fungicide. You don't absolutely have to go out and buy a new sprayer.”
“Coverage of the canopy is the key,” Pedersen says. ASR tends to infect the soybean plant from the bottom up. Even with a lack of specific knowledge about how ASR will spread geographically in the U.S., the experts agree that the key to successfully battling the disease with fungicides starts with effectively penetrating the soybean canopy.
Depending on the geographic location and weather conditions, ASR can infect the plant at a variety of growth stages. However, from the research and the disease's performance in South America, it seems that rust is most likely to infect the crop from the R1 to R3 growth stage in many parts of the country. As Miller relates, there are several ways to penetrate the canopy of plants at this growth stage: “Change your nozzles, make sure your pump capacity is adequate, increase your pressure and increase your carrier rates per acre and you will do, on average, a pretty good job of penetrating the canopy and reaching the middle and lower leaves on the soybean plant with a fungicide.”
Pedersen urges producers and applicators to strictly follow fungicide label directions regarding proper application rates and pressures. Because the recommended application pressure depends upon the fungicide product, there is not necessarily a one-size-fits-all pressure recommendation. “It is particularly important since a Section 18 versus a Section 3 label may differ. Many times labels will indicate a minimum of 30 to 35 psi or above,” Pedersen says.
Spray at higher pressures
Troy Schroeder, AGCO Application Equipment, reminds producers that fungicides often have to be sprayed at a higher pressure than herbicides. “Typical herbicides are applied at 20 to 30 psi, whereas fungicides are more typically applied at up to 70 psi, with 30 psi at the low end,” he states. “Make sure your pump and all of the components in your spray system are able to apply at that pressure.”
Marty Heyen, Spraying Systems Company, TeeJet Spray Products, agrees. “It is hard to throw out a minimum pressure; you won't see many applications below 30 to 40 psi. So that range is probably the minimum,” he says. “There is some misinformation out there about the need to have a lot higher spray pressures to spray the fungicide for Asian soybean rust. It isn't necessarily the case. Producers need to be able to manage droplet size just as they manage other variables, such as speed and application volume. You can get the appropriate droplet size at 40 to 50 psi; you just need to make sure you select the right nozzle.”
The John Deere research shows that while low pressures will still work in many cases, it seems the optimum application pressures are in the slightly higher range. “Pressure is very critical,” Miller explains. “We saw a dramatic improvement in coverage by applying at pressures more than 50 psi on average. Greater than 50 psi across all applications showed more than a 50 times greater improvement in both coverage and penetration into the lower part of the canopy versus less than 50 psi. You need to maintain a medium-sized droplet at these high pressures.”
Apply a finer droplet size
“According to current research, medium- to fine-sized droplets of 200 to 250 microns seem to work best for fungicides,” relates AGCO's Schroeder. “We recommend a wide-angle, flat-fan nozzle, and many experts are recommending using this nozzle in a twin-nozzle configuration with one nozzle spraying in a forward direction and one spraying toward the rear.” Miller says the Spraymaster Ultra Lo-Drift tips and angled spray caps, called TwinCaps, performed well in the John Deere studies.
Heyen says TeeJet is also recommending several nozzles, some of which have been on the market for quite some time. The TeeJet TwinJet nozzle, for example, has been available for more than 10 years and has been proven to be very effective in applying fungicides in other types of crops. The nozzle produces two flat-fan sprays, each with a 110° spray angle. There is a 60° offset between the two nozzles, which means it is spraying 30° forward and 30° backward in the direction of travel.
“As you spray over that crop, you are actually hitting the plant surface twice, and because you are spraying at an angle, it helps to penetrate the canopy as well,” Heyen says. The TwinJet produces a fine- to medium-sized droplet at recommended operating pressures.
Use extra volume
Will Smart, Greenleaf Technologies, says while droplet size, pressure and nozzle orientation are important considerations when selecting a nozzle, carrier rate, sprayer speed and timing are also critical.
Some chemical manufacturers are recommending producers spray upwards of 15 to 20 gal./acre because the extra volume will help get better penetration and coverage in a dense crop canopy. According to John Deere's Miller, “We started seeing significant coverage improvement above 10 gal./acre in Brazil, and we really started seeing significant increases in mid- and lower-canopy coverage at 15 to 20 gal./acre, which looked the best.”
Mark Mohr, Hypro spray tips product manager, says not only are application rates higher for treating ASR, but agitation may also need to increase. “The applicator needs to be concerned not only about delivering enough spray to the boom to deliver the 20 gal./acre, but also has to think about agitation in the spray tank. Many of the fungicides are flowable formulations that require good, thorough agitation to keep them mixed up to spray effectively.”
Check sprayer pump
Andy Randle, vice president of sales and marketing, ACE Pumps, encourages producers to check their sprayer pumps ahead of time. “We have a flow calculator available on our Web site at www.AcePumps.com where people can check to see if their pump will do what they want it to when it comes to Asian soybean rust,” Randle says. “In many cases, the pump they have will probably do the job. Producers may want to consider using jet agitators, which require less flow to agitate the tank.”
Producers need to pay close attention to tendering capacity and logistics when applying at the higher rates, because sprayers will not cover as much ground between fills. Schroeder reminds producers to make sure there are enough nurse trucks to get water to the sprayer so they don't lose time waiting for trucks to show up.
Speed is yet another key to effective spraying. Miller says the John Deere data suggest less than a 10% difference across the average canopy penetration when applying fungicides in a range of 8 to 18 mph.
TeeJet's Heyen says operators may want to slow down for better placement of chemical on the crop and into the canopy. Lower speeds also help eliminate “boom bounce,” which occurs when the boom does not stay stable as the sprayer is traveling over the field.
“When spraying for Asian soybean rust, the boom height is going to need to be in the neighborhood of 12 in. above the crop,” Schroeder notes. “University recommendations are to have the boom positioned as close to the crop as possible and still maintain a 30% overlap.”
Pedersen tells producers that now is the time to gather the information about fungicides, get the equipment ready and formulate a plan of attack.
“The best thing producers can do is to be ready, scout the fields and follow how the pathogen is moving,” he says. “Go to a lot of meetings and get all the information you can get. The worst thing you can do is not to prepare and to just ignore this. If it doesn't show up, then at least we were prepared.”
FOR MORE INFORMATION
Hypro: “Delivering Solutions for Asian Soybean Rust” brochure available at www.HyproPumps.com.
TeeJet: “Proper Application Techniques Are the Key to Controlling Soybean Rust” brochure. Learn more at www.teejet.com.
RoGator: “Spraying Fungicides Is Different” guide. Obtain the spray guide online at www.rogator.agcocorp.com, or call 877/454-3346.
Greenleaf Technologies: Visit www.turbodrop.com/asr_nozzle.html to learn more about nozzles for soybean rust.
ACE Pumps: Visit www.AcePumps.com for resources to help calculate pump flow.