Controlled-release formulations field testing

Because of the complexity of real systems, inhibitor selection is by far not straightforward and requires testing by laboratory and field studies. Commercial formulations usually contain a combination of several active inhibitors, blended with a specific surfactant/solvent package, which controls the release of the inhibitors into the environment (i.e. the available inhibitor concentration). The protection of multimetal systems requires particular care, since efficient inhibitors for one metal may be ineffective or even corrosion-accelerating for another metal. In general, the performance of formulations depends on the system parameters and has to be evaluated by field tests to ensure protection. 

Satisfactory formulations of pheromones that afford a constant release rate over a long period of time are not likely to be achieved without the cooperation of the chemical industry. Controlled release of pheromones is discussed in the Proceedings of a recent symposium (623). Fortunately, several organizations in the U. S. have been interested in the possibilities of the use of pheromone formulations on a commercial basis. One company (605) has supplied formulations for several investigators, and in addition has carried out extensive field tests with their own personnel. It has developed the use of hollow fibers, which are simply microcapillary reservoirs that serve to contain a vaporizable material and mediate evaporation of the material into the atmosphere . The fiber wall is essentially impermeable. One end is sealed, and the release rate essentially depends on diffusion from the surface of the liquid-vapor interface to the open end of the hollow fiber. Fibers are supplied in two forms. A tape form consists of a parallel array of fibers on an adhesive tape this form is used to establish point-source evaporators. The chopped fiber form is used for dissemination with a ground rig or from the air. 

Another company (624, 625) supplies a controlled release dispenser, which is a three-layer plastic laminated sheet consisting of a bottom protective layer, a middle pheromone reservoir layer, and a top permeable layer through which the pheromone diffuses. The sheet can be cut into ribbons and applied over an area. Formulations have been field tested on a number of insect pests gypsy moth, pink bollworm, peachtree borer, lesser peach tree borer, soybean looper, cabbage looper, European elm bark beetle, tobacco budworm, fall armyworm, tussock moth, eastern spruce budworm, and Mediterranean fruit fly. 

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