ette. Other products may also have information on the label as to the target pH of the spray solution.
ANTI-FOAMING AGENTS AND SPRAY COLORANTS
Anti-foaming agents are used to reduce air entrapment in the spray mixture that may occur during agitation or spraying. Foaming of the spray solution can create problems in mixing or application. Colorants are used to cause the treated area to be colored to ensure complete coverage of the spray solution over the desired target area. In citrus, colorants are frequently added to the spray mixture when treating stumps of trees that have been removed due to various reasons. The colorant will remain on the cut surface to indicate that the stump has been properly treated with herbicides to inhibit regrowth.
DRIFT CONTROL AGENTS
Drift control agents will increase the average droplet size when the solution is sprayed. Larger droplets are less likely to drift (move away from the target site) as compared with smaller droplet sizes. The use of drift control agents can be very important if applying products that may impact sensitive crops or plants which may be located near the application site. There are no drift control agents available to completely eliminate drift.
When mixing any two or more products together to create a tank mix, it is always wise to make sure this new pesticide solution will not damage the crop or create a combination that will not mix evenly in the tank. The pesticide mixture should not create clumps or separations in the spray tank, causing an uneven application of the spray mixture.
Common causes of incompatibility could include impurities in the spray tank or water, order in which the pesticides were mixed into the tank, types of formulations being used, water pH and/or amount of time the mixture has been in the tank.
When mixing pesticides together into the spray tank, follow the W-A-L-E mixing order:
- add enough water to fill the tank about one-half full or one-half of the desired spray volume. Any water-conditioning agents should be added to the tank at this time;
- add the wettable (W) powders;
- agitate (A) the spray solution;
- add the liquids (L); and,
- add the emulsifiable concentrates (E) to the spray solution last.
Adding the emulsifiers to the tank first makes it very difficult for the wettable powders to evenly mix into the spray solution. During this entire process, the agitation systems should be operating to keep the solution mixed during the filling process. After adding each material to the tank, the pH of the spray solution should be checked to make sure it is not too high or too low. Any necessary pH adjustments should be done as needed prior to the addition of pesticides. Once all materials are added and mixed, the tank should be filled to the desired level based upon the desired mixture concentration. If possible, the agitation system should be running until the entire tank mixture is applied. If the entire spray mixed volume is not able to be applied, the tank agitation system should be run for a sufficient time to ensure all materials that may have settled to the bottom of the tank are evenly mixed back into the spray solution.
Source of information: Applying Pesticides Correctly, Fred Fishel, SM1, University of Florida.
Stephen H. Futch is an Extension agent at the Citrus Research & Education Center, Lake Alfred, FL.