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Pennsylvania Turfgrass – Michael Fidanza, Ph.D., Professor of Plant and Soil Science Pennsylvania State University, Berks Campus, Reading, PA and John Kaminski, Ph.D., Professor of Turfgrass Science Pennsylvania State University, University Park, PA

The late Dr. Houston Couch (1924 — 2004), published a series of three articles in 1984 and 1985 on methods, techniques, and other factors to improve fungicide applications to turf. He was a turfgrass pathologist at Pennsylvania State University early in his career, and at Virginia Tech for the remainder of his career. In 2002, he received the prestigious GCSAA Col. John Morley Distinguished Service Award, and was recognized in 2003 with the USGA Green Section Award. Since those ‘Dr. Couch articles’, there have been many advances in spray application equipment and technology over the past several years in both the agricultural and green industry sectors, as well as research on making adjustments to spray nozzles to improve or ensure product delivery and performance. Let’s revisit water-carrier spray volume and spray tips or nozzles.

Water-Carrier Volume. In golf course turf management, a commonly accepted rule-of-thumb is to calibrate your sprayer to deliver 1 (one) gallon of water-carrier per 1000 square feet for fairways, tees. and roughs, and 2 (two) gallons water/1000 sq ft for greens. That 1 gallon amount also is common for sports turf, lawns, and sod farms. Incidentally, 1 gal/1000 sq ft equals 43.56 gal water per acre, and 2 gal/1000 sq ft equals 87.12 gal water per acre. Some turf managers use an even 50 gal water per acre (which is 1.15 gal/1000 sq ft) or 100 gal water per acre (which is 2.3 gal/1000 sq ft). Of course, more water-carrier volume translates to longer time required to operate the sprayer and repeatedly fill the spray tank to make product applications. In turf management, we don’t have the option of flying an air- plane over a site and making aerial spray applications at a low volume of 5 gal water/acre as is the case with field crops. Proper and effective spray applications take time, and of course employee safety is a top priority.

The proper water-carrier volume is important to ensure accurate delivery and distribution of the product to ensure optimum product performance and efficacy, and to legally follow product label instructions. It also means driving your sprayer as slow as 3 to 4 mph across the turf, or walking a ‘spray hawk’ across greens, so it does take time. Calibrate your sprayer or spray system for the proper ground speed and pump pressure to deliver the amount of water-carrier volume you desire and train your employees to check the calibration periodically throughout the “spray season”.

Nozzles. The nozzle or spray tip represents the last piece of equipment to come into contact with the spray solution before it reaches the turf. Don’t let the least expensive part of your sprayer be responsible for a very expensive mistake. The nozzle forms the spray solution into spray droplets and a spray pattern. After all the careful calculations of product rates and timings and formulations, and careful calibration and maintenance of your sprayer, it all comes down to water droplets. Regularly check all nozzles on the spray boom for wear or damage, and periodically measure water output from each nozzle to ensure the same amount is dispensed or at least within 5% variance among all the nozzles along the spray boom. And what about nozzle spacing? Whether you prefer a 10″ boom height or 20″ boom height (i.e., distance from the turf surface to the bottom of the nozzles on the spray boom), make sure the space between the nozzles is equal to the boom height in a “1-to-1” ratio. For example, for a 20″ boom height, the nozzles should be spaced 20″ apart.

There are many nozzle-types available, but they are all responsible for forming the spray droplets and spray pattern. For turf applications, the flat-fan spray pattern is preferred, not a hollow cone pattern. The flat-fan spray pattern delivers a uniform distribution of droplets evenly across the turf surface. The hollow cone spray pattern is good for certain pesticide applications in production agriculture and orchards but will not produce a uniform or evenly distributed amount of spray droplets on a flat turf surface.

Among the many flat-fan nozzles, the TeeJet brand XR (“extended range”) nozzle is commonly used in turf applications and produces the classic flat-fan spray pattern. Keep in mind there are many other nozzle types and brands available. The TurfJet nozzle is also considered a standard flat-fan nozzle, but the droplets produced are very large, resembling raindrops. These larger water droplets are good for reducing drift, but compromise on getting uniform and complete coverage. The air induction (AI) nozzle also produces a flat-fan pattern and is constructed to draw air inside to mix with the spray liquid resulting in a larger droplet filled with an air bubble but very few fine droplets prone to drift. The AI nozzle will not eliminate spray drift 100%, but it will dramatically and effectively reduce drift compared to the other nozzle types. There are many flat-fan nozzle choices, and other nozzle types and brands available. Whichever nozzle you choose, a good rule-of-thumb is to be sure the nozzle produces spray droplets of medium or coarse or very coarse size, which is best for fungicide applications to turf. Be sure to review the nozzle manufacturer’s information (i.e., tables and charts, or mobile ‘apps’) so you are sure to select the best nozzle for your intended use, the appropriate sprayer operating pressure and sprayer travel speed, and any other recommendations necessary to ensure success.

Spray nozzle turrets have become common on spray booms and provide the option of having two to three to five different nozzle types at the ready. If you want to try a different nozzle or a new and improved nozzle, apply water through it onto water sensitive paper and visually check for uniform and complete coverage (water sensitive spray cards available at gemplers.com). Operate the sprayer and groundspeed and operating pressure as recommended by the manufacturer or as you have it calibrated and see if the nozzle you chose provides the coverage you need. Also, frequently inspect the nozzles for clogging or other malfunctions, and don’t forget to verify that the product(s) in the spray tank solution have dissolved and is(are) in proper suspension. And of course, keep accurate records to ensure legal compliance as well as having the “recipe” (i.e., best water-carrier volume and nozzle-type) for maximizing your spray applications.

References

Couch, H.B., J.M. Garber, and D. Jones. 1984. Turfgrass fungicides, part I: Application method and effectiveness. Golf Course Management 52(7):40, 42-43, 46, 48, 50-52.

Couch, H.B. 1984. Turfgrass fungicides, part II: Dilution rates, nozzle size, nozzle pressure and disease control. Golf Course Management 52(8):73-76, 78, 80.