As stated on the product label of Bonide Mancozeb Flowable with Zinc Concentrate, "The addition of an agricultural surfactant will improve fungicide performance by providing a more uniform spray deposit, increased foliar redistribution, and improved fungicide retention during periods of wet weather." Please be sure to review the product label for complete application instructions before use. Also, to add the surfactant, you will need to follow the instructions on the label for the one that you select to use.