Spray deposition and distribution in a bay laurel crop as affected by nozzle type, air assistance and spray direction when using vertical spray booms

Bay laurel, a commercially grown evergreen ornamental plant and economically important for Flanders (Belgium), is very susceptible to pests. Pest management usually consists of spraying pesticides using handheld application techniques which are labour-intensive, involve a high risk for operator exposure, and provide only suboptimal biological control. One alternative, a vertical spray boom, was evaluated in a bay laurel crop pruned into a conical shape. Different spray boom configurations were by attaching water sensitive papers to a model that emulated the size and shape of the trees. The optimal nozzle type was determined by deposition measurements in an actual laurel crop. Three application rates were tested, 2450, 4900 and 7200 L ha-1 of ground surface. The most efficient spray application technique was found to be an extended range flat-fan, an air included flat-fan or a hollow cone nozzle, all at 4900 L ha-1 resulting in the highest relative spray deposits and the most uniform spray distribution in the canopy.