It is sometimes desirable to add certain materials (adjuvants) to fungicide spray solutions to improve final results or to resolve problems with application. Adjuvants have been developed to improve spray dispersion, reduce volatility, spray drift, and foaming, improve plant penetration, buffer spray solution, plus other functions. The most commonly used adjuvants are non-ionic surfactants. Surfactants reduce surface tension of spray droplets which allows better plant coverage. Without surfactants, droplets roll off hard to wet plant surfaces. Additives or adjuvants can be placed in one of the following categories:
Diluents – any liquid or solid material used to dilute active ingredient and make it less concentrated.
Surfactants – materials added to a fungicide formulation to ensure that powders are easily wettable and well dispersed in the spray tank.
Spreader-stickers – materials used to increase the spreading of spray droplets on plant surfaces and render the residue more tenacious.
Modifers – compounds added to pesticide formulations to enhance biological activity or reduce plant damage.
Some fungicide formulations contain compounds that act as surfactants. In these cases manufacturers may not suggest a surfactant be added to the spray mixture. In other cases, and in particular with wettable powders, labels may emphasize the need for a surfactant to enhance effectiveness. If a chemical label does not specify the use of an adjuvant, one should realize that he assumes the risk of undesirable results if any should occur. The safest approach is not to use adjuvants unless the label so specifies.