Control of phytophthora brown rot of citrus fruits¹

Abstract

Control of brown rot of citrus fruits, using the new anti‐oomycete systemic fungicides, has been studied in the field and in packing houses under the climate conditions of Spain. In the field, in rainy weather and at the stage of colour‐break of the fruits, both with artificial inoculation and with natural infection by Phytophthora citrophthora, a single treatment with fosetyl‐A1 at 0.4% a.i. as a foliar spray provided good control of the disease. The highest fungitoxic effects were reached 14–21 days after treatment. Copper oxychloride + mancozeb at 0.3% a.i. showed moderate efficiency. In semi‐commercial experiments in the packing house and in the laboratory, fosetyl‐A1 at 0.3% a.i. strongly controlled infection with zoospores located in different layers of the fruit peel (flavedo or albedo). Fosetyl‐A1 also developed good efficacy in healthy fruits, protecting them from infection by contact. Metalaxyl at.0.2% a.i. also reduced infection by zoospores and contact. Oxadixyl, propamocarb and folpet (reference product) had poor activity against the brown rot fungus. All these data strongly support the value of fosetyl‐A1 for control of brown rot disease of citrus fruit in the field and in the packing house as a post‐harvest treatment. Metalaxyl may also be utilized for this purpose.

Branch cankers on citrus trees in Spain caused by Phytophthora citrophthora

“…During recent decades, brown rot of citrus fruit has been the disease of greatest economical importance in Spain. The main species associated with brown rot was P. citrophthora ; but other Phytophthora species such as P. nicotianae and P. hibernalis were also reported (Tuset, 1977; Tuset et al ., 1990).…”

“…In contrast to P. nicotianae , P. palmivora is able to produce abundant sporangia on affected fruits and they are recognized as an important inoculum source in brown rot epidemics (Timmer et al ., 2000). Brown rot in Spain is mainly associated with P. citrophthora and there are some reports of its sporulation on affected fruits on the tree (Tuset, 1977, 1983; Tuset et al ., 1990), but more work is needed to establish a relationship between fruit sporulation and branch infections. Some Phytophthora ‐induced diseases are known to be spread by pests, ants, rodents and snails from soil to aerial host sites (Taylor & Griffin, 1981; El‐Hamalawi & Menge, 1996; Konam & Guest, 2004).…”

Estudios de etiología, epidemiología y control de un nuevo síndrome de lesiones en tronco y ramas principales de cítricos asociado a Phytophthora.

“…En España, las especies P. parasitica y P. citrophthora están ampliamente distribuidas en todas las plantaciones citrícolas del país como los agentes causales de la "gomosis", "podredumbre del cuello" y "aguado de los frutos" (Tuset, 1977(Tuset, y 1983Tuset et al, 1990).…”

“…Durante las últimas décadas, el "aguado de los frutos" ha sido la enfermedad ocasionada por Phytophthora de mayor importancia económica en el país. La principal especie asociada con el "aguado del fruto" ha sido P. citrophthora; sin embargo, otras especies tales como P. parasitica y P. hibernalis Carne han sido también citadas (Tuset, 1977;Tuset et al, 1990). …”

“…A diferencia de P. parasitica, P. palmivora es capaz de producir abundante cantidad de esporangios sobre frutos afectados lo que involucra una importante fuente de inóculo en epidemias de "aguado de fruto" (Timmer et al, 2000). El "aguado de frutos" en España se asocia principalmente con P. citrophthora y existen varias citas de su esporulación sobre frutos afectados en el árbol (Tuset, 1977(Tuset, y 1983Tuset et al, 1990). No obstante, se necesita más investigación para establecer la relación entre la esporulación del fruto y las infecciones de ramas.…”