Many pesticides require the addition of an adjuvant, and some do not. When applying fungicides, insecticides or herbicides without a recommended adjuvant, 30 percent to 50 percent reduction in pest control can be expected. Adjuvants may cause damage to a plant if the wrong adjuvant is used or if it is used at too high a concentration. Using the correct adjuvant on a greenhouse crop is a critical decision. This bulletin is intended to describe how adjuvants differ and what adjuvants are best to use.