The EU has adopted a framework directive on the sustainable use of pesticides1. Already many countries have defined 'no spray' buffer zones to protect special areas, such as open surface water, drinking wells and buildings.
The Crop Adapted Spray Application (CASA) system has been developed as part of the ISAFRUIT project2. It consists of three sub-systems that detect a number of important crop and environmental variables and adjusts the spray accordingly. The sub-systems are:
- A Crop Health Sensor that identifies the health of the fruit crop.
- A Crop Identification System that identifies the size and density of the tree canopy.
- An Environmentally-Dependent Application System (EDAS) that identifies environmental conditions, such as wind speed and direction as well as the presence of nearby sensitive areas.
The study investigated the effectiveness of the EDAS, which measured the wind speed and direction to understand the risk of the spray reaching unintended areas and adjusted the droplet size accordingly. If there is a large likelihood of drift, it makes the droplets bigger so there is less risk of the spray drifting to other areas.
The EDAS also identifies the geographical position of the sprayer and works out the distance to the edge of the orchard and if there are any sensitive areas nearby. The EDAS then adjusts the air flow to the left or right with a fan system.
A field test of the sprayer was conducted in an orchard and its performance compared with that of a conventional sprayer. There were several different situations that varied the position of the sprayer in the orchard and the speed of the side wind. The results demonstrated that the EDAS could recognise the environmental conditions and respond accordingly by altering the air flow and the droplet size. It reduced the drift by 44 to 83 per cent compared with a conventional spray system. When using large droplets, drift was reduced by over 80 per cent. Reducing the drift had little effect on how the spray was deposited compared with conventional systems.
The results indicate that the EDAS part of the CASA system effectively reacts to environmental conditions. This could be particularly useful for growers who have orchards next to areas that need protection from pesticides. The researchers point out that there may be concern amongst growers that a coarser and more targeted spray would produce poorer coverage. Although research indicates that this is not the case, this may need to be communicated to growers.