Herbicides and fungicides can be mixed, but specific conditions must be met; otherwise, efficacy may be reduced, or crop damage may occur.
The feasibility of mixing depends primarily on the properties of the chemicals, the crop type, and the application environment. Before full-scale application, it is advisable to conduct a small-scale compatibility test: mix small amounts of the chemicals in a transparent container and observe for precipitation, flocculation, or layering. If any of these phenomena occur, the chemicals should not be mixed.
1. Principles of Mixing
Mixing pesticides requires adherence to several key principles: physical compatibility (no chemical reaction upon mixing), maintenance of efficacy, no increase in toxicity, and safety for the crop. For example, alkaline pesticides (such as Bordeaux mixture) often lose effectiveness when mixed with most acidic herbicides, while mixing most sulfonylurea herbicides with common fungicides carries a higher risk of adverse effects.
2. Common Combinations
In practice, some farmers mix glyphosate with certain systemic fungicides, or combine difenoconazole with fenoxaprop-P-ethyl in wheat fields. However, such practices require strict adherence to the mixing recommendations found in product labels or consultation with local agricultural technical services.
3. Precautions
Pay attention to the order of mixing: generally, add wettable powders first, followed by suspension concentrates, and finally emulsifiable concentrates or aqueous solutions, stirring thoroughly after adding each component. The mixture should be used promptly and not allowed to sit for extended periods. Additionally, mixing pesticides in high-temperature and high-humidity environments increases the risk of crop damage.
4. Alternatives
If compatibility cannot be confirmed, it is recommended to apply the chemicals separately, with an interval of at least seven days between applications. Furthermore, ensure that the first chemical has been fully absorbed or degraded before applying the second one.
