Pesticides applied in irrigation water (chemigation) may require modified formulations for effective and safe application. Currently available insecticide formulations produce variable insect control when applied through chemigation systems. Pest control is greatly influenced by the chemical properties, e.g. solubility in water and organic solvent. When emulsified formulations or technical pesticide are added to a nonemulsified oil, significantly better control of foliar-feeding insects is obtained compared to emulsified formulations applied with conventional-ground applications. Chemigation of technical-oil formulations of insecticides may allow for reduced active ingredient for effective insect control.
Currently available herbicide formulations produce varied weed control when applied through chemigation, depending on application to soil or foliage, the volume of irrigation water, and the chemical properties of the compound. Water-soluble herbicides applied postemergence produce the most varied results, while water-insoluble and emulsified concentrates produce the most consistent weed control. Herbicides applied preemergence through chemigation are equal to, or more effective than, conventional applications. Addition of a petroleum or vegetable oil carrier to a formulated or technical herbicide generally improves its performance when applied through chemigation. An increase in the volume of irrigation water used to apply the chemical also decreases the weed control.
Nematicides, applied through chemigation, give excellent nematode control whenever soil moisture and water rates are controlled to prevent leaching below the bioactive zone. The addition of a nematicide to a nonemulsified oil generally improves nematode control and helps modify the effect of excess moisture.
Fungicides, as currently formulated, give good disease control when applied through chemigation with minimal volume of water. The addition of a nonemulsified oil improves the performance to both flowable and oil-soluble fungicides.