Assessment of the influence of working pressure and application rate on pesticide spray application with a hand-held spray gun on greenhouse pepper crops

Choosing the appropriate machinery for applying pesticides is crucial. Despite the availability of technologically more advanced equipment, the hand-held spray gun is still widely used today for spraying greenhouse crops because of its ease of operation and its low economic cost. Growers believe that a high spray application rate and a high pressure are needed to achieve good pest and disease control. In this study, the effects of pressure and volume application rate for application of treatments using a hand-held spray gun to greenhouse pepper crops were evaluated. In the first case, three different pressures were assessed: a reference at 2000 kPa (P20) and two others at 1500 kPa (P15) and 1000 kPa (P10). To test the effects of application volume, three application volumes were used: one considered to be reference (V100), applied by an experienced grower, and two reductions thereof, i.e. 25% (V75) and 50% (V50). Each test was made at two different stages of crop development. The results showed that the use of high pressures did not improve either the deposition or the penetration into the crop canopy and the losses to the ground were not significantly different. On the other hand, a reduction by some 25% of the application rate routinely used by local farmers caused major reductions in deposition on the plant canopy, which might possibly compromise pest and disease control. The losses to the ground diminished with the application rate, although differences were not significant between V100 and V75.