TENACITY AND PERSISTENCE OF COPPER FUNGICIDES IN CITRUS SEEDLINGS UNDER SIMULATED RAINFALL

ABSTRACT The amount of fungicide that adheres to the leaf during spraying and the amount that remain on the leaf after weathering are the main factors that defines the amount of active residue on the leaf surface to effectively control plant pathogens. Thus, the objective of this work was to evaluate the tenacity and persistence of copper in citrus seedling leaves under simulated rainfall in Jaboticabal, State of São Paulo, Brazil. The evaluated variables were copper content, solution retention, surface tension and drop spectrum. A significant and inversely proportional linear relationship to drops <100 µm was found. The percentage of copper retained in leaves of citrus seedlings with copper fungicides of suspension concentrate (SC) formulations after simulated rainfall was greater than 80%. Copper fungicides of SC formulations presented the lowest surface tension, allowing greater tenacity and persistence of copper on seedlings of citrus leaves after simulated rainfall and increased contact between the drops and leaf surface.

The effect of application of copper fungicides on photosynthesis parameters and level of elementary copper in hops

Photosynthesis and transpiration rates in the interval of 30 min before and 30 min after copper fungicide application show an increase from the level of 5.0 to 7.0 &micro;mol CO₂/m²/s and 0.75 to 1.00 mmol H₂0/m²/s. Long-term measurements show that the increase of photosynthesis rate after copper application is temporal and fades away after 10&minus;14 days. No stress response was induced after the application of copper fungicides. Contents of copper in hop cones are up to 500 mg/kg if total amount of applied copper does not exceed 15 kg/ha. Contents of copper on leaves are 2&ndash;5 times higher at the same application dose. Application of 5 kg copper per one hectare of vigorous growth of Agnus variety increases content of copper on hop leaves by 1000 mg/kg at least. The same amount of copper increases its content in hop cones by 300 mg/kg at the ripening period. Tight correlation between the amount of copper applied and its content in hops does not exist. Elementary copper from leaves is brought into harvested hops in the form of biological admixtures. Copper content in hop cones shows a decreasing trend, which is given by gradual increase of cones size at the ripening period. Similar trend on hop leaves shows that washing off and dissolving of copper compounds by atmospheric water can participate in this process as well. Common content of copper in untreated hop cones and leaves is up to 20&minus;25 mg/kg. &nbsp; &nbsp;

The effect of copper fungicides on the rate of photosynthesis and the transpiration of hop plants

The paper evaluates the effect of copper fungicide spraying on the rate of photosynthesis and transpiration of hops, the influence of spraying on the elemental copper content in the leaves and cones hop variety Agnus. Photosynthetic rate was measured by LC pro+ (infrared analyzer) in the Hop Research Institute Saaz in the field in some periods of 2008, 2009 and 2010. Dry cones and leaf samples (taken before and after application of copper fungicides) were analyzed in an accredited laboratory for elemental copper.