Water sensitive papers simulation to assess deposits on targets

Aim of the study is to assess the possibility to use water sensitive papers to estimate, beside the superficial coverage, also the amount of deposit on the target at varying the spray features. To point out the main quantities influencing the deposit, the behaviour of the water sensitive papers was simulated by assuming some simplifying hypotheses: log-normal distribution of the diameter population of the drops and circular spots. Several images (630) of water sensitive papers, sprayed with drops of different mean diameter (from 100 up to 500 μm), constant coefficient of variation (0.50), and theoretical percentage of covered surface ranging from 10 up to 100%, were produced by means of simulation. These images were considered as effective water sensitive paper images and then analysed by means of an image processing software. The correlations between measured and effective values were studied and they allowed for an estimate of deposit and spray features from the image data. This implies that the analysis of the water sensitive paper images allows the determination of more complex parameters such as the unitary deposit and the impact density, all data strictly related to the efficacy of a phytosanitary treatment.