Deposition and distribution of myclobutanil and tebuconazole in a semidwarf apple orchard by hand-held gun and air-assisted sprayer application

BACKGROUND Sprayers have been shown in numerous reports to influence pesticide deposition and distribution significantly, and public concern for their potential risk has been increasing in recent years. In this study, a hand-held gun sprayer and two air-assisted sprayers (a conventional axial fan air-blast sprayer and a tower sprayer) were used to apply myclobutanil and tebuconazole, and their influence on pesticide distribution and deposition in a semidwarf apple orchard was systematically investigated. RESULTS The coefficients of variation of different canopy zones associated with the tower sprayers were 38.9-41.9% for leaves and 35.5-36.4% for fruit, generally lower than the coefficients of variation related to the other two sprayers. Tests conducted using the air-assisted sprayers recorded an overall higher drift on the adjacent rows than experiments carried out with the hand-held gun sprayer. The results of drift in soil indicated that pesticide was mainly distributed within 5 m downwind of the treated area, and the distribution pattern was influenced by sprayer design. The total pesticide concentration deposited in soil within 5 m during application by the tower sprayer was 0.28 m mg kg(-1)for myclobutanil and 0.90 m mg kg(-1)for tebuconazole, much lower than that of the hand-held gun sprayer and the conventional axial fan air-blast sprayer. CONCLUSION The results indicate that the tower sprayer gives a more uniform distribution and guarantees better effectiveness for the phytosanitary treatment. The tower sprayer also protected the soil better and reduced environmental pollution due to its scientific structural design.