Principles of spray application

Spray application is a critical activity for grape and wine businesses – spanning the issues of food safety, environmental stewardship, community welfare and profitability. 

Efficient spray application requires equipment that is matched to the grapevine target, an appropriate dose of agrochemical and minimal loss of spray to the ground or to drift. 

Photo: Wine Australia

The efficacy of spray application depends on various elements including sprayer type, nozzle type and sprayer set-up, tank mix and adjuvants, sprayer technologies, buffer vegetation and weather conditions.

A wide range of spraying units are available in Australia. Some of the main types include air blast sprayers (axial fan type), directed air duct sprayers, multi-head axial fan sprayers, cross-flow fan sprayers, air-shear sprayers, tunnel and recycle sprayers

There are several key considerations for sprayer unit selection and optimised coverage. These include nozzle types and positions/angles, air speed and volume output, and air direction. Several sprayer technologies are now available that can facilitate improved spray deposition including sensor systems,   electrostatic sprayers and tunnel and recycle sprayers.

The combined ingredients of agrochemicals in the spray mixture affect droplet formation, physical properties (droplet bounce, spread or sticking), evaporation rates and the efficacy of active ingredient of each product.  Adjuvants are used to influence properties of the spray solution and improve the performance of active ingredient on the grapevine. 

The weather has a significant impact on spraying efficacy. High air-temperature and low relative humidity result in high evaporation rates which reduce droplet survival times in the air and on the target. Surface temperature inversion can have a significant impact on the efficacy of spraying and spray drift. Spraying should usually be done where wind speeds are between 3 and 15 km/h. Densely planted trees or shrubs within the vineyard or on property boundaries can form useful barriers to prevent spray drift.    

Videos

The principles of spray application (2013)

Vineyard spray application - new technologies (2014)

Vineyard spray application - regulation & legislation update (2014)