Efeito de fungicidas cúpricos, aplicados isoladamente ou em combinação com mancozeb, na expressão de sintomas de fitotoxicidade e controle da ferrugem causada por Puccinia psidii em goiabeira

Abstract

RESUMO -Dois experimentos foram conduzidos em pomares de goiabeira 'Paluma', nos municípios de Monte Alto e Vista Alegre do Alto-SP. No primeiro experimento, avaliou-se o efeito de formulações de fungicidas cúpricos, aplicados isoladamente e em mistura com mancozeb, quanto ao efeito fitotóxico em botões florais e em frutos de goiabeira, em três estádios de desenvolvimento. No segundo experimento, foram avaliados os mesmos fungicidas usados no primeiro experimento, sendo, porém, acrescido do tratamento constituído por tebuconazole, cujo alvo foi sua eficiência no controle da ferrugem. No primeiro experimento, verificou-se que nenhum dos fungicidas testados causou abortamento de flores ou outros tipos de sintomas de fitotoxicidade em frutos de tamanho inferior a 15 mm de diâmetro. Contrariamente, estes fungicidas, quando aplicados isoladamente, em frutos entre 25 a 35 mm de diâmetro, causaram sintomas severos de fitotoxicidade. Em frutos de tamanho superior a 40 mm de diâmetro, estes fungicidas causaram sintomas de fitotoxicidade de níveis leves a moderados. A combinação de fungicidas cúpricos com mancozeb causou sintomas de fitotoxicidade em níveis leves, enquanto com mancozeb isoladamente não foram verificados sintomas de fitotoxicidade. No segundo experimento, verificou-se que os fungicidas cúpricos, aplicados isoladamente, foram eficientes no controle da ferrugem da goiabeira, apresentando eficiência comparável ao tratamento-padrão representado por tebuconazole. Esta eficiência foi também observada mediante o emprego da combinação mancozeb e óxido cuproso ou hidróxido de cobre. Termos para indexação: Psidium guava, Erwinia psidii, fungicidas, manejo integrado EFFECT OF COPPER FUNGICIDES, SPRAYED ALONE OR IN COMBINATION WITH MANCOZEB, IN EXPRESSION OF PHYTOTOXICITY SYMPTOMS AND RUST CONTROL CAUSED BY Puccinia psidii IN GUAVAABSTRACT -Two experiments were carried out in guava orchards cv. 'Paluma' at Monte Alto and Vista Alegre do Alto/SP. In Experiment 1 it was used copper fungicides applied alone and in combination with mancozeb to evaluate the effect of phytotoxicity on floral buds and guava fruits in three developmental stages. In Experiment 2 it was used the same fungicides used in Experiment 1, plus a treatment with tebucunazole in order to evaluate the rust control. In Experiment 1 none of the fungicides tested caused phytotoxicity symptoms and abortion of fruits less than 15 mm in diameter. The fungicides caused higher phytotoxicity in fruits between 25 and 35 mm but not in fruits larger than 40 mm diameter. Copper fungicides combined with mancozeb lead to a slight toxicity, but when applied the mancozeb alone did not lead to phytotoxicity sympton. In The Experiment 2, it was observed that copper fungicides applied alone were efficient to control rust as well as the combination of mancozeb and cuprous oxide or hydroxide and the fungicide tebuconazole.

Guava fruit loss caused by rust

“…Each organic fungicide was sprayed five times alternatively with copper oxychloride (2400 mgL -1 ) at biweekly intervals after the disease was first detected. However, copper fungicide was sprayed only at the initial fruiting stage, when fruits were smaller than two cm in diameter, to avoid injuries to larger fruits (13,25). Treatments stopped at the end of the susceptible phase, when fruits reached approximately four cm in diameter (26).…”

“…On the other hand, rust is a serious hazard to guava commercial production in Brazil; it is caused by the fungus Puccinia psidii Winter and is the most common and disseminated aerial disease affecting Myrtaceae in American countries. When P. psidii epidemics affect 'Paluma' cultivar, the most important commercial guava variety in Brazil, frequent fungicide spraying is required (9,13). However, the effect of rust on guava yield has not been experimentally quantified yet.…”

Pruning Time in Two Production Systems in the Guava Tree Bacterial Blight Control

“…The diseases control of the guava tree aerial part was carried as conventional production protocol (FISHER et al, 2011;GOES et al, 2004;IDE;MARTELLETO, 2008), applying alternately different organic and cupric defensives. The herbicides use was incorporated to the conventional production system, where every 60 days there were systemic post-emerging (glyphosate, 2 L ha -1 ) and of contact (paraquat dichloride, 2 L ha -1 ) herbicide application over the spontaneous plants and weeds.…”

“…This way, the soil organic matter has a direct correlation with the soil cationic exchange capacity. Consequently the green fertilization use, dead coverage or vegetal, organic fertilization by composting and liquid fertilization or with bioactive compounds; may be one of the instruments to recover the soil and leaf surface biodiversity vitality (HALFELD-VIEIRA et al, 2008;2015;TOMITA 2010;PANE et al, 2012;REZENDE et al, 2008).…”

“…The studies about the interactions between the biological control agents with the microbiological community of the enviroment are very complex, just like the quality and quantity effects of managed compounds on the soil., (HOITINK;CHANGA, 2004) and on the leaf surface (HALFELD-VIEIRA et al, 2008;2015), these may also be the plants vitality elements of success on field conditions. Therefore, this work´s objective was to evaluate the bacterial disease control and yield on guava tree exposed to different pruning seasons in organic and conventional system.…”