Spray drift continues to be an important issue for commercial pipfruit growers Offtarget agrichemical movement was determined from the Hawkes Bay Focus Orchard on two occasions Canopy development had a major influence on spray drift with 25 times less drift from a fully foliated canopy compared with a dormant canopy The proximity of the sprayer relative to the edge of the sprayed block was an additional major factor influencing spray drift Results are compared with those found in previous New Zealand and overseas studies and management strategies for spray drift minimisation are discussed
Research from 1989 to 1996 into drift from air blast orchard spraying, principally in kiwifruit blocks with live shelter, is reviewed. A mass balance study showed 96% of applied vinclozolin could be accounted for with 75% on the target crop, 19% on the ground or shelter and about 2% leaving the block as drift. Summarising results from 21 trials gave trends for both deposited and aerial drift outside the shelter to decrease exponentially with distance (distance for 50% decline, d 0.5 , ca. 26 m). Chlorpyrifos, pirimiphos-methyl and particularly diazinon gave elevated drift levels that persisted after spraying ceased. This was attributed to volatilisation from the crop. Typical drift levels for a range of pesticides were 0.5-5mg/m 3 in air samples and 20-200 mg/m 2 in deposits 50 m downwind of shelter. Air measurements in urban areas 0.5-1 km from orchards detected low levels of chlorpyrifos and diazinon (5-40 ng/m 3 ). Drift levels were not strongly influenced by formulation, water rate (500-2150 litres/ha) or wind speed (0.5-5 m/sec). Risks to human health from drift outside sprayed blocks were assessed as minimal.
In 1981-82, and 1982-83 trials were carried out on kiwifruit to examine the effectiveness of the controlled droplet application (CDA) spraying technique. Spraying was done at 60 and 50 litres/ha (total volume) over 2 full seasons using a rotating disc CDA sprayer developed at the NZAEI. A 1 year spraying programme involving the application of 200 litres/ha (total volume) of spray with a spinning cage CDA sprayer was also performed. Treatment included applications at half and three-quarters of the recommended chemical rate. The performance of these sprayers was compared with conventional high volume airblast and hydraulic units (2 250 litres/ha). Export spray program~es based on azinphos-methyl pre and post flowenng, followed by monthly applications of phosmet and/or diazinon, were used. Results were assessed on the basis of chemical residue analyses and pest infestation on leaves, and fruit damage: All treatments at full chemical rate gave excellent control, and it is possible that chemical rates can be reduced.
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