Sources and Concentrations of Cupric Fungicides for the Control of Citrus Black Spot1

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.

An overview of the most threating diseases that affect worldwide citriculture: Main features, diagnose, and current control strategies

“…CBS has been first seen in Australia nearly 120 years ago (Kotzé, 1981), and it is now distributed in Africa, Asia, Australia, the Americas (Serra et al, 2022) (Table 1). The CBS disease was responsible for ~40% of production losses in South Africa, Brazil, Australia, and the USA (Savi et al, 2019;Tranet al, 2019;Franco et al, 2020). Figure 2 indicates some important information about CBS, such as causal agent, main symptoms, control strategies, and dissemination forms.…”

Enhancing the efficiency and sustainability of foliar fertilization in agriculture

“…This explains why calcium carbonates (CaCO3), oxides (CaO), and silicates (Ca2O4Si), when applied via foliar sprays, are recommended for protecting plants from sunburn and acidic rainfalls (Silva et al, 2022) rather than as effective sources of calcium (Ca 2+ ). The same is true for copper oxides (CuO), hydroxides (Cu(OH)₂), and oxychlorides (Cu₂(OH)₃Cl), which function as contact fungicides and bactericides rather than as copper sources for plants (Franco, Goes, & Pereira, 2020).…”

Caracterização do >i<mating type>/i<, otimização na produção de ascósporos e influência da temperatura e molhamento na germinação de esporos de >i<Phyllosticta citricarpa>/i<

“…Outros meios e condições de incubação têm sido utilizados, como discos de folhas de citros autoclavadas e depositadas sobre meio ágar-água 3% a 25ºC sob luz contínua ou ½ BDA a 24ºC sob fotoperíodo de 12 horas (WANG; DEWDNEY, 2019). As avaliações de germinação de conídios em laboratório geralmente são realizadas com concentrações de 10 4 conídios/mL, enquanto a inoculação do patógeno via conídios em plantas são realizadas com 10 5 conídios/mL (FRANCO et al, 2020;SAVI et al, 2018;. No entanto, a produção de ascósporos possui lacunas que precisam ser preenchidas em aspectos como a quantidade de ascósporos produzidos por cada metodologia, quando se inicia e termina a produção e como se comporta ao longo do tempo tal produção sob diferentes condições de cultivo e cruzamentos.…”