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58 p r a c t i c a l w i n e r y & v i n e ya r d a p r i l 2 0 1 4 g r a p e g r o w i n g R ecommendations for pesticide application have been made on a "per acre" basis, and growers have applied them on a per-acre basis. During my 34-year career as a pest control adviser I have recommended pesticide applications on a per-acre basis. At the annual Farm Safety Day, in Lodi, Calif., I teach a class about how to cali- brate spray rigs on a per-acre basis. Astute growers have observed that this practice does not really make sense, and I have readily agreed with them. In fact, entire countries, having realized this, have abandoned the practice. I think the time has come for us to take a closer look at the use of per-acre spray calibration. Acramite 50WS. The label calls for a dose of 0.75 to 1 pound per acre. If you apply 0.75 pounds per acre in a vineyard with 12 feet between vine rows, then you are applying 0.75 pounds per 3,630 linear feet of vine row. Another way to say this is that you are applying 3.3 ounces of Acramite per 1,000 feet of vine row. Now let's imagine that you are apply- ing 1 pound of Acramite per acre in a vineyard with 9 feet between vine rows. That means that you are applying 1 pound per 4,840 linear feet of vine row. Another way to say this is that you are applying 3.3 ounces of Acramite per 1,000 feet of vine row. In one vineyard, you applied Acramite at the low end of the label rate, and in the Larry Whitted BY Why 'per acre' spray dose calibration no longer applies This article was originally written for the Lodi Winegrape Commission's Coffee Shop blog, a viticulture research and practice information resource available at lodigrowers.com. More information about the Coffee Shop: Welcome to the Coffee Shop: One of the Lodi Winegrape Commission's (LWC) chief objectives is to provide Lodi (Crush District 11) winegrow- ers with opportunities to learn about sustainable winegrowing. In an effort to continue our tradition of innovate extension, the LWC has launched a new grower-oriented website (lodi- growers.com), which strives to be a one-stop shop for practical winegrow- ing information. Among the website's many features is the Coffee Shop, a viticulture research and practice blog. Rural cof- fee shops have long since been favor- ite gathering places where farmers come together to catch up on local happenings and share farming knowl- edge about the weather, new techno- logical innovations and market trends. The Coffee Shop was designed to be a virtual gathering place where Lodi winegrowers and other viticulture pro- fessionals can learn from one another. The contributing authors include viti- culture consultants, PCAs, University of California Extension farm advisors, industry leaders, university scientists and growers themselves. The Coffee Shop aims to bring a grounded perspective to cutting edge research and innovative prac- tices and technologies. For questions about the Coffee Shop or to submit an article, contact Matthew Hoffman at matthew@lodiwine.com. Photo suPPlied BY on tArget sPrAY sYstems yard where the trial was conducted, then you do not know how much pesticide was actually applied per 1,000 feet of vine row. If we are going to continue to talk in terms of per-acre dose, then we need to know the tractor row width in the vine- yard where the research was conducted. Either that, or the research needs to be reported in terms of linear feet of vine row rather than on a per-acre basis. The same logic applies to sales or technical presentations in which the pesticide dose is given on a per-acre basis. When we talk about per-acre pesticide dose, we are speaking in terms of area-based calibration, and the unit of measure is the acre. When we talk about pesticide dose per 1,000 feet of vineyard row, then we are There are 43,560 square feet in an acre. If we were spraying alfalfa then we would spray all 43,560 square feet, but we are not. We are spraying vine rows, and the amount of vine row in one acre depends on the space between the vine rows. If a vineyard is planted with 12-foot-wide tractor rows, then 1 acre consists of 3,630 linear feet of vine row per acre. If a vine- yard is planted with 9-foot-wide tractor rows, 1 acre consists of 4,840 linear feet of vine row per acre. A highly effective and fairly expensive miticide applied by some Lodi growers is other vineyard you applied it at the high end of the label rate. However, in each case you applied 3.3 ounces per 1,000 linear feet of vine row. In other words, although the per-acre dose rate was completely differ- ent, the actual dose arriving on the grape- vine canopy was exactly the same. This is the new math: 0.75 pounds equals 1 pound! Or at least it can, depend- ing on the tractor row width. This is important because research trial results are reported based on a certain pesticide dose per acre. However, if you do not know the tractor row width of the vine- (Continued on page 68)