Effect of sprayer speed and nozzle type on spray distribution and biological efficacy in potato late blight control.

摘要

In a series of experiments performed in the laboratory the effect of spray distribution of two nozzle types applying different spray qualities at two forward speeds were assessed in relation with spray deposition and biological efficacy against late blight in potatoes. A comparison was made between two sizes of a standard flat fan nozzle and a venturi type flat fan nozzle all sprayed at 3 bar pressure, applying a spray volume of 65, 130 or 270 L ha-1 with increasing coarseness of the spray quality. Potato plants were placed underneath a moving traverse system as in a field distribution. Spray deposition was quantified using a tracer added to the spray liquid. Spray deposition was determined on top, middle and bottom leaf levels of the potato plants. In a separate spray application six doses between 0-100% of the advised dose of Shirlan (fluazinam) were applied to determine biological efficacy of the applied spray distribution. Data on spray distribution and protection against potato late blight are presented for the different nozzle types and sprayer speeds. With advised dose rates no differences in biological efficacy occurred between the standard and venturi flat fan nozzle types. At low dose rates and a spray volume of 135 L ha-1 the standard flat fan nozzle better protected the potato foliage against late blight than the venturi flat fan nozzle. Higher forward speeds reduced the spray volume with the same nozzle type and gave an increased risk for late blight infection at the advised dose rates.