Plant-specific and canopy density spraying to control fungal diseases in bed-grown crops

摘要

Matching spray volume to crop canopy sizes and shapes can reduce the use of plant protection products, thus reducing operational costs and environmental pollution. Developments on crop adapted spraying for fungal control are highlighted in arable cropspraying. A plant-specific variable volume precision sprayer, guided by foliage shape and volume (canopy density sprayer; CDS) was developed for bed-grown crops to apply fungicides. Sensor selection to quantify crop canopy and spray techniques to applyvariable dose rates are evaluated based on laboratory measurements. Sensor-nozzle combination delay time was determined for the different nozzle settings and combinations. Optimal sensor-nozzle distances could be determined to specify sprayer design. Based on the laboratory experience a prototype CDS sprayer was built using either a Weed-IT or a GreenSeeker sensor to detect plant place (fluorescence) or size (reflectance). Variable rate application was either done with a pulse width modulation nozzle ora Lechler VarioSelect switchable four-nozzle body. Spray volume could be changed from 50-5501/ha in 16 steps. Spray deposition, biological efficacy and agrochemical use reduction were evaluated in a flower bulb and a potato crop during field measurements using a prototype CDS sprayer. Spray volume savings of a prototype plant-specific sprayer are shown to be more than 75% in early late blight (Phytophthora infestans) control spraying in potatoes. In flower bulbs (lily) it was shown that in fire blight(Botrytis spp.) control on average spray volume could be reduced by 45%. In a potato crop biological efficacy was maintained at the same good level as of a conventional spraying. In a flower bulb crop biological efficacy of the CDS was lower than of conventional spraying, which means that spray strategy and dose algorithms need further research.