Abstract
ABSTRACT Citrus black spot (CBS) is a severe disease for citriculture in the São Paulo State, Brazil. Part of its management is focused on chemical control using cupric fungicides and strobilurins. The objective of the present work was to evaluate the efficacy of three sources and three concentrations of cupric fungicides (copper hydroxide, copper oxychloride and cuprous oxide). Orange fruits of the Pera cultivar were bagged in the plants and the treatment with cupric fungicide was applied. The fruits were inoculated (by spray) with Phyllosticta citricarpa (1×104 conidia mL-1) after 0, 7, 14, 21, and 28 days, and bagged again. The evaluation of incidence and severity was did at the harvest time of fruits. A second experiment was conducted under natural infection with the same treatments, consisting of application of fungicides at the stages F1 (petal fall) and F2 (fruits with diameter of 1 cm), using mechanized sprayer with mean flow of 7.35 L solution plant-1. Subsequently, all treatments received four applications of azoxystrobin (30 g ha-1), plus mineral oil at 0.25%. Four monthly evaluations were done to determine the CBS incidence and severity. The initial applications with cupric fungicides are essential for the control of CBS; the fungicide copper hydroxide showed the best control of CBS with the lowest rate of metallic copper (43.7 g of Cu++ 100 L-1) in both experiments, regardless of the conduction conditions.
Highlights
Citrus black spot (CBS) is caused by the fungus Phyllosticta citricarpa McAlp. (BALDASSARI; WICKERT; GOES, 2008), and is associated with citrus plants in several countries in Africa, Asia, Oceania (KOTZÉ, 2000; EPPO, 2017), South America and North America, and in Caribe (TIMMER et al, 2000; SCHUBERT et al, 2010; HIDALGO and PÉREZ, 2010)
The initial applications with cupric fungicides are essential for the control of CBS; the fungicide copper hydroxide showed the best control of CBS with the lowest rate of metallic copper (43.7 g of Cu++ 100 L-1) in both experiments, regardless of the conduction conditions
All treatments with the highest rates of cupric fungicides presented on average lower incidence and severity of citrus black spot (CBS) (Table 2)
Summary
Citrus black spot (CBS) is caused by the fungus Phyllosticta citricarpa McAlp. (teleomorph: Guignardia citricarpa Kiely) (BALDASSARI; WICKERT; GOES, 2008), and is associated with citrus plants in several countries in Africa, Asia, Oceania (KOTZÉ, 2000; EPPO, 2017), South America and North America, and in Caribe (TIMMER et al, 2000; SCHUBERT et al, 2010; HIDALGO and PÉREZ, 2010). The control of CBS is done usually by using fungicides; in Brazil, it is controlled mainly with use of cupric and strobilurin fungicides (MOTTA, 2009; VINHAS, 2011; SILVA JÚNIOR et al, 2016). The rates used at the stages F1 and F2, and in subsequent applications in combination with strobilurins for the control of CBS under field conditions vary, and are usually based on the fungicide metallic copper contents. These recommendations are from studies with copper oxychloride; no studies comparing sources and concentrations of cupric fungicides are found
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