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New Zealand Plant Protection 66 (2013): 199-203

The effect of rainfall on copper spray residues on kiwifruit foliage, fruit and canes

R.E. Gaskin, D.B. Horgan, K.D. Steele and R.M. van Leeuwen

ABSTRACT

Copper sprays are known to have protectant activity against the bacterial disease Pseudomonas syringae pv. actinidiae (Psa), but their longevity on kiwifruit vines was unknown. Commercial copper sprays were applied using a moving head tracksprayer to the fruit, foliage and canes of Hayward kiwifruit after which simulated rain was applied in incremental amounts up to 100 mm. The copper sprays were moderately resistant to rain wash-off on leaves with at least 25 mm of rain required to remove 50% of the initial residues. Copper sprays applied to both kiwifruit canes and fruit were highly resistant to rain washoff with up to 100% of the initial spray deposits still present after 50 mm of rain. Up to four sequential copper sprays on fruit are unlikely to exceed maximum residue limits for fruit even in the absence of rain.

Keywords: copper sprays, residues, rain resistance, kiwifruit.

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