Factors influencing the performance of spray delivery systems: A review of recent developments

The need for designers and users of pesticide application equipment to balance the risk of off-target contamination with high product efficacies when using the minimum dose of active ingredient has led to the requirement for more data defining the performance of such equipment. Measurements of the droplet size distribution in sprays from conventional nozzles has shown acceptable levels of consistency between data obtained with different measuring systems enabling such sprays to be classified providing that systems are calibrated with agreed reference nozzles. For sprays with air inclusions different measuring systems have been shown to give comparable and consistent results, and there is now a need to fully integrate such sprays into a revised classification scheme. Temperature of both spray liquid and the surrounding air have been shown to influence droplet size distribution measurements. It is therefore proposed that measurement protocols specify a maximum difference in temperature between the spray liquid and surrounding air of 5 degrees C. For boom sprayers it is not possible to predict accurately the risk of drift from droplet size measurements alone because of the complex detrainment mechanisms involved. It is proposed that standardized wind tunnel procedures be defined that enable the relative risk of drift from different nozzle designs to be quantified. In the future it is likely that more of the information relating to application system performance will be delivered pre-programmed in the units control system or as part of a decision support system.