Replacement of spray nozzle tips based on operational considerations.

In the residual spraying of insecticides, application of the correct dosage is important both to obtain the optimum effectiveness and to avoid wasting insecticide. One of the main factors controlling dosage is the discharge rate of the sprayer, which depends to a great extent on the ability of the nozzle tip to discharge an even spray. However, nozzle tips are subject to erosion and their output increases with use, especially when water-dispersible-power formulations of insecticide are used. To reduce wastage of insecticide, nozzle tips are changed periodically but the tips are expensive and the replacement schedule should be based on the cost of the tip in relation to the cost of the insecticide wasted. A theoretical approach is discussed and a practical method for establishing a replacement schedule on economic considerations is suggested.