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• TurboDrop TwinFan for Coverage Critical Applications (Tabulation Chart)

Despite the proliferation of information becoming available on Asian Soybean Rust, there are still many questions concerning proper application techniques. While there is some debate as to the most effective way to apply Rust fungicides to the target, some existing techniques for spraying fungicides into crop canopies may prove useful for combating Soybean Rust.

Following droplet size and carrier rate recommendations on the chemical label is most important. Approved fungicides show an average application rate between 15 and 20 GPA. Additional information is available from chemical representatives, county extension agents, and university researchers.

Coverage, Penetration, and Drift Control
Both the protective and curative fungicides require excellent coverage to be effective. While some have the ability to translocate, they are not systemic. Coverage and timing are critical. Since the disease starts in the lowest parts of the soybean plant and works its way upward, it is important that the spray penetrate through the canopy to get down to the area where it is most needed. The spray must not only penetrate the canopy, but also offer good coverage, and, because it is toxic to humans and birds, should be resistant to spray drift. Until recently, the combination of drift reduction, canopy penetration, and good coverage was difficult to attain.

Conventional spray nozzles operating at moderate pressures (30-40 psi) can produce medium to fine droplet sizes that provide excellent coverage, but, because of their small size and lack of velocity, the droplets do not penetrate a crop canopy very well. Increasing the pressure of these nozzles makes the droplets even smaller and they begin to drift and evaporate.

TurboDrop for High Pressure Canopy Penetration
Over the last 10 years, we have found that the TurboDrop® nozzle at higher pressure will penetrate a canopy better than conventional hollow cones, flat fans, or twin fans. At pressures from 70-150 psi, TurboDrop® nozzles produce larger, high velocity droplets that are filled with air bubbles. These fast moving droplets have enough energy to penetrate the crop canopy, and when they strike the target, they spread out or explode, providing excellent coverage. In fact, the TurboDrop® was designed specifically for high pressure canopy penetration with contact chemicals requiring excellent coverage.

The TurboDrop nozzle has been used to penetrate dense cotton canopies since 1995. Insecticides and defoliants require thorough coverage throughout the cotton canopy. It is not unusual for cotton to reach heights of 5 to 6 feet. Using the TurboDrop® nozzle at 70-120 psi in these coverage critical applications has produced excellent results.

TurboDrop TwinFan for High Pressure
More recently, we have found that the TurboDrop ® Venturi with a dual flat spray outlet can provide even better chemical efficacy in crops where canopy penetration is important, such as potatoes, lettuce, pineapples and peanuts. The TurboDrop® TwinFan is available in a full polyacetal and semi-ceramic configuration. The full polyacetal version (TDTF) features a polyacetal pre-orifice and dual polyacetal outlet nozzles, one oriented 30 degrees forward and the other 30 degrees backward. The semi-ceramic version (TDCTF) features a ceramic pre-orifice and dual polyacetal outlet nozzles arranged the same way. The forward outlet nozzle will produce smaller droplets in a 110° spray angle while the rearward outlet nozzle will produce larger droplets in an 80° spray angle. At higher pressures (70-150 psi) the droplet size of these nozzles will be in the 200-300 micron range (ASAE Fine-Medium), which has proven to provide excellent efficacy when using TurboDrop® nozzles with contact pesticides. For most TurboDrop® TwinFan configurations, the forward spray is Fine and the backward spray is Medium. The Fine droplets will be captured primarily in the upper part of the canopy, while the Medium droplets are intended to penetrate into the middle and lower part of the canopy.

Many farmers have used this combination of the TurboDrop® Venturi with a TwinFan for a variety of applications, including insecticides in lettuce and pineapples, Liberty® herbicide in corn, fungicides in potatoes and wheat, and more. For best canopy penetration, operate the TurboDrop® TwinFan nozzles at higher pressures, higher carrier rates and slower travel speeds.

While the TurboDrop® TwinFan nozzle consists of three primary components (the Venturi air injector, the TwinFan adaptor and two polyacetal tips) the ISO color coded Venturi determines the flow rate. Optimizing droplet size and velocity, as well as, carrier rate with the TurboDrop® TwinFan will ensure effective penetration and coverage with Soybean Rust fungicides.

Dual AirMix for Medium Pressure
When the sprayer is limited to lower pressures of 50-70 psi, another option is the AirMix® TwinFan configuration. The AirMix® TwinFan provides the opposing angles of entry into the canopy like the TurboDrop TwinFan, and is able to produce the Fine-Medium spray spectrum at this lower pressure range. A variety of AMTF combinations can be utilized to deliver an even wider variety of flow rates (see chart). For example, an AM11002 with an AM110015 would give the flow rate of an 035 nozzle. This AMTF035 would deliver 16gpa at 60psi at 8mph (on 20” spacing).

Double Coverage with One Pass
As many researchers and product labels suggest, the small to medium (200-300 micron) droplet size, produced at slightly higher than normal pressures, will provide effective penetration and coverage for Rust fungicides, especially when a dual fan configuration is used. (See “Strategy Required to Win War Against Soybean Rust,” www.stopsoybeanrust.com/viewStory.asp?StoryID=95.) Both the TurboDrop TwinFan and the AirMix TwinFan can produce the appropriate droplet size with enough pressure to push the droplets into the canopy.

The TDTF at 70-120+ psi and the AMTF at 50-80 psi will deliver the 200-300 micron droplet size, while limiting the Very Fine, drift prone droplets (less than 100 micron) which readily move off target and evaporate.

While the standard TurboDrop® (TDXL) and AirMix® (AM) nozzles have proven to provide excellent canopy penetration into a wide variety of dense crops at higher pressures, the added benefit of twin or dual fan orientation for shorter dense crops like soybeans has been shown to accentuate penetration and coverage in these types of canopies. Research with potatoes and peanuts, two crops with similar canopies to soybeans, indicates that forcing the spray droplets into the foliage with a double fan configuration can increase coverage in the bottom half of the canopy. To maximize the effectiveness of Soybean Rust fungicides, a dual air injected spray nozzle offers a unique means of delivering the right size droplets to the intended target.