Minimizing environmental impact of pesticide applications in orchards and residues on fruits

In the EU-FP6 ISAFRUIT project a Crop Adapted Spray Application (CASA) system for precision orchard protection was developed. The system consists of three components: Crop Identification System – CIS, Environmentally Dependent Application System – EDAS, and a Crop Health Sensor – CHS. The CIS and EDAS components were assembled onto a orchard sprayer that minimizes spray drift by nozzle size (droplet size) selection and air support settings, and by the use of ultrasonic sensors that recognize the shape of the trees, thereby adapting spray volume to tree canopy volume. The CHS is the ultimate sensor that can recognize a disease. Altogether, the sprayer should minimize chemical residue in fruits and the environmental impact of agrochemical applications in orchard sprayings.

To develop the CHS spectral analysis has been used, based on the developments in crop sensing techniques for grassland and arable crop production. Crop health status, with as an example the infection of apple scab (Venturia inequalis) on apple leaves, has been evaluated. The early detection of apple scab using spectral reflectance on the leaf opens new ways to develop a Crop Health Sensor (CHS) to be used for apple scab detection in the orchard and adapt the crop protection strategy as well.
Application technique (i.e. sprayer type, sprayer settings and nozzle type), crop architecture and growth stage have all been shown to affect variability in deposit and residues on fruits.
Different components of the CASA-system have been evaluated for deposition and residues on fruits; e.g. the effect of droplet size (nozzle type) on pesticides residues on apples and was evaluated in a commercial orchard. In general, the mean residue levels for the coarse and fine droplet applications did not differ significantly. However, large variations in residue levels were observed between the individual apples, either sprayed with coarse or fine droplets.