Local redistribution of fungicides on leaves by water

SUMMARY Local redistribution of various fungicides applied as large or small droplets to detached broad‐bean leaflets was examined by laboratory bio‐assay with Botrytis fabae and by leaf‐printing techniques. The results showed that fungicidal particulate and soluble material will spread in water from the initial deposits and that the protected areas on leaves inoculated after washing were often much greater than on unwashed leaves. The extent of redistribution was related to the inherent toxicity, physical form, duration of weathering and tenacity of the fungicides. The effects of formulating copper oxychloride and zineb fungicides with surface‐active agents and adhesives seemed due to differences in the tenacity of the deposits. Results indicated that similar types of redistribution would occur in the field, but the possible importance of the electrokinetic theory of redistribution was not proven.