Small plot evaluation of pesticides provides critical information for pesticide developers as well as for end users in cotton and other crops. Accurate pesticide placement by spray equipment is becoming increasingly important as is the environmentally proper handling of rinsate or leftover materials following the spray operation. This paper describes a computer controlled spray system which provides optimum precision during pesticide application and provides for environmentally clean handling of rinsate and small amounts of pesticide mixtures remaining in the system following pesticide application. The controller prepares the spray system for loading of the pesticide to be sprayed, and, following initiation by the operator, automatically governs spray, rinse, and system purge operations prior to loading another compound. Manual override is available at any time, and a panic button is available to close all operations in case of an operational emergency. Rinsate is collected in a holding tank for proper disposal following the application of all treatments in a trial.