charge based upon the pH of the spray solution. The most commonly recommended surfactant is a non-ionic type; however the type selected should vary depending on the pesticide or pesticides chosen.
An emulsion is a mixture of two liquids that are incompletely mixed. Emulsifying agents promote the suspension of one liquid into the other. The two common types of emulsifying agents are oil-in-water or water-in-oil mixtures. The oil-in-water emulsion agents are used to get an oil-soluble pesticide dispersed in a water mixture, thereby allowing it to be sprayed in a water-based solution. When water and oils are mixed, they will form an invert emulsion that creates a thick solution that will resist drift, improve rainfastness or delivery of the product. In some cases, an invert emulsion may be too viscous (thick) to be applied with conventional sprayers. Mayonnaise and butter are two examples of invert (water-in-oil) emulsions in which water is dispersed in vegetable oil or animal fat, respectively.
Wetting agents will decrease the surface tension of the mixture, which allows a larger portion of each spray droplet to contact the surface of the vegetation. Wetting agents increase the coverage of the spray solution, thereby increasing the effectiveness of the pesticide due to increased coverage of the target surface.
CROP OIL CONCENTRATE
Crop oil concentrates are phytobland petroleum or vegetable oils that are formulated to increase the absorption of the pesticide solutions through the cuticle or waxy layer of the leaves. Crop oils contain an emulsifier that aids them in mixing with water. Crop oil concentrates are usually 80 percent to 85 percent petroleum or vegetable oil and 15 percent to 20 percent emulsifier. Product labels will specify if a petroleum or vegetable oil formulation should be used.
Silicone-based surfactants reduce the water surface tension, which allows the water to spread outward onto the leaf surface as compared to beading up on the leaf surface like water on a recently waxed surface. Silicone surfactants can be used at very low rates ranging from as low as 0.10 percent to 0.25 percent volume/volume basis.
Stickers make the pesticide solution adhere to the plant foliage to a greater degree as compared with solutions that do not contain a sticker. By increasing the adherence to the foliage, runoff of the spray mixture, wash-off during rain or irrigation and/ or the evaporation of the pesticide from the target surface are reduced. By minimizing pesticide losses, the effectiveness of the pesticide application will increase.
Compatibility agents are utilized when two or more products are incompatible with each other and are added to the same spray mixture. This could be a physical or chemical incompatibility which causes uneven distribution in the spray tank. The compatibility agents will aid in suspension of the pesticide into the spray solution.
ACIDIFIERS AND BUFFERS
The pH of the spray solution will vary greatly depending on the water source as well as products being mixed into the spray tank. Well water pH from underground sources will usually range between 7.0 (neutral) to 9.0 (alkaline). The pH can vary significantly with season and source.
Most pesticide applications are recommended to be applied at a pH of 5.5 to 7.0. As the pH increases above 7.0, some pesticides are subject to degradation. In most cases, the buffers should be added to the solution to reduce the pH to the desired range before adding the pesticide. As each pesticide is added to the tank, the pH should be rechecked to ensure the modified solution is still within the recommended pH range.
Acidifiers are added to the pesticide spray solution when the mixture is alkaline (pH > 7.0) and the need exists to neutralize the solution to a lower pH. Buffers will change the pH of the water solution, which will be maintained even if the pH of the solution changes.
In the case of Aliette, the label states that buffering to pH 6 or higher is recommended to avoid phytotoxicity when copper has been used prior to, with or following the application of Ali