Affordable precision application for drift reduction while maintaining biological efficacy often seems to be an unreachable goal in day-to-day operations. Optimize one aspect and the others suffer. As more attention is focused on drift reduction, the trade-off can come in the form of reduced efficacy.

An innovative approach to achieving off-target deposition reduction and optimization of biological activity without sacrificing either is being taken by Waldrum Specialties, Inc. The company, located in southeastern Pennsylvania, is combining its expertise in spray nozzle design and development with a carrier to provide an integrated approach for maintaining biological efficacy while managing spray drift.

Since its founding by John "Tex" Waldrum and Dody Pfizenmaier in 1981, the intent has been to continue, and expand, Waldrum's ideas for improvement of agricultural spray application devices, and spray nozzles in particular. Named as inventor on nineteen United States patents, the most recent in 1996, Mr. Waldrum obviously does not lack for new approaches to old problems.

The simple, consistent theme of products from Waldrum Specialties will be very familiar to everyone concerned with reduction of off-target spray movement: Narrow the spray droplet spectrum. Reduce the large number or very small droplets responsible for most off-target movement, and reduce the small number, but high volume fraction, of large droplets which decrease target coverage and efficacy. The goal, economically unobtainable in real world applications, being production of a spray having a single size for all droplets. However, the closer you approach the ideal, the more efficient the application.

As its first products the company offered, and continues to supply, nozzles which product a large average droplet size, with high droplet size uniformity. Production of large average droplet size, as application engineers are well aware, is one of the first methods employed to reduce off-target movement. As application engineers and biologists are well aware, the larpe droplet drift reduction solution does not always allow for expression of maximum biological activity. Large droplets have a, relatively, high volume; the higher the droplet volume the more difficulty in producing enough droplets to achieve complete coverage of the target.

Beginning about seven years ago, Waldrum Specialties struck out to find another solution. Again, the goal can be simply stated: While maintaining a narrow droplet size spectnum, decrease the average droplet size. Decrease average droplet size and target coverage goes up; increased target coverage equals increased biological efficacy and, other factors remaining constant, more favorable costs. The result of Waldrum's work is the company's patented Thinvert® system.

The concept behind the Thinvert® system will be immediately obvious to anyone who has participated in the Spray Drift Task Force or attended most any agricultural formulation and application symposium. Match the nozzle and the fluid being delivered to the target.

John Waldrum has designed a nozzle, actually a series of nozzles, to produce a uniform, small average droplet size spray. Waldrum and Roy Johnson, the company's biological expert and field project coordinator, have developed a fluid carrier with those physical properties which compliment the nozzle design.

The carrier portion of the integrated system is a thin, low viscosity, oil-in-water emulsion. Readers will understand that for proprietary reasons it is not possible to identify which fluids are utilized, nor the exact properties of a particular fluid which affect performance. We can say, however, that these fluids allow formulation of low viscosity invert emulsions with surface tension appropriate for generation of the desired droplet spectrum, and that the volatility of these fluids is low enough to assist in maintaining acceptable droplet size while in-flight water evaporation is decreasing droplet size.

The carrier is intended to be generic. That is, Waldrum Specialties does not sell active ingredients, but rather a system for application of appropriate active ingredients. Thinvert® carrier is compatible with emulsifiable concentrates, water-based concentrates, and certain solid concentrates. You might think of the carrier as, approximately, being just a substitute for spray tank water. Incompatibilities are in those circumstances where the end-use product being diluted with, or dispersed into, the carrier causes a large increase in viscosity. High pound-per-acre wettable powders are one example. On the other hand, water dispersible granules with a low per-acre use rate are quite acceptable.

Of course functional fluids are more expensive than water, usually. Applications for the Thinvert® system are intended for situations where the total application rate, carrier plus end-use product, is in the low volume category, i.e., a few gallons/acre or liters/hectare.

One instance where water is not inexpensive and off-target movement reduction is very important occurs in weed control along railway tracks in the western United States. You might keep this in mind as an example for out-of-the-box thinking. Railroad companies need to suppress, for a variety of reasons, weed growth around railroad tracks.

In the western part of the U.S., the distances between the start and finish of a treatment section go to the hundreds of miles. Water has always been a scarce commodity in this area. So, the lower the application volume, assuming acceptable weed control, the more cost efficient the treatment. At the same time, rail rights-of-way pass through crop farm lands. Off-target movement (drift) is quite unacceptable. Thinvert® is well suited to this application, and has been accepted.

While non-agricultural uses of Waldrum Specialties spray nozzles and Thinvert® system have been predominant to date, the company is actively pursuing the agricultural crop market. Field tests and demonstrations are ongoing for both ground and aerial application.

Summaries of issued U.S. patents covering Thinvert® (U.S. 5518183, 5248086), and prior work, can be found by searching the U.S. Patent and Trademark Office WWW site (http://www.patents.uspto.gov) using John Waldrum as the named inventor.