The deposit pattern of a spray cloud is affected by the micrometeorological conditions at the time of application technology, new insecticides requiring lower dosages or volumes of application and the need to prevent damage to the environment as a result of drift or double swathing, it is essential that all pesticide applicators make use of available knowledge pertaining to meteorological factors affecting spray drift and deposit. Basic equipment requirements for determining suitability of weather conditions for spraying are described.