Investigation of phytotoxicity regarding copper fungicides applied to apples
Mario LEŠNIK, Stanislav VAJS, Vesna GABERŠEK and Vili KURNIK
pp. 55-59
ABSTRACT
The influence of adding kaolin clay (Cutisan), pine resin (Nu-Film), and milk proteins (ProNet-alfa) to copper fungicide spray at the same levels of phytotoxicity was tested regarding copper fungicides when applied to 'Golden Delicious' apples tested during a field-trial. Copper fungicides were applied 8 times per season using a standard orchard sprayer (250 l/ha of spray), starting at the BBCH 71 stage (fruitlets with more than 15 mm diameter); and continuing throughout the season until stage BBCH 79, at the rate of 250 g Cu++/ha at each application. The phytotoxicity levels of traditional copper fungicides (sulphate, oxy-chloride, oxide, hydroxide) were compared to fungicides based on copper complexes (gluconate, EDTA chelate, peptidate and aminoacid complexes). Fruit disorders were evaluated (malformations, surface-russet). The level of reduction in phytotoxicity when adding kaolin clay was 10 to 80% and reached from 10 to 40% when adding pine resin. The addition of milk proteins in some fungicides reduced phytotoxicity by 5 to 10%, whereas in others a 15 to 30% increase was observed. The content of copper was determined in the fruits at harvest-time. The use of additives generally increased the copper residues of the fruits. The highest increase was determined for pine resin (5-100%), moderate for milk proteins (5-70%), and the lowest for kaolin clay (0-30%). The results of our trial showed that the tested additives had different effects on the reductions of phytotoxicity regarding copper products, and the intake of copper ions to apple fruits. They were very specific in terms of compatibility with different formulations of copper fungicides. In regard to compatibility, kaolin clay had the most neutral effect. As the addition of pine resin and milk proteins can significantly increase the copper content of fruits, they were less suitable as additives for the reduction of phytotoxicity within certain formulations of copper fungicides.
Key words: apple, copper, phytotoxicity, additives, kaolin clay, pine resin, milk protein
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