EFFECT OF CONVENTIONAL AND ALTERNATIVE PRODUCTS ON POSTHARVEST DISEASE CONTROL IN AVOCADOS

Ivan Herman Fischer,Juliana Cristina Sodário Cruz,Maria Cecília De Arruda Palharini,Matheus Froes De Moraes,Mirian De Souza Fileti,Ana Carolina Firmino

doi:10.1590/0100-29452018408

Abstract

ABSTRACT Postharvest diseases constitute a serious problem for avocado commercialization. Thus, the present study aimed to evaluate the effect of conventional and alternative products in controlling diseases affecting ‘Hass’ avocados in the field and in the postharvest by carrying out physicochemical characterization of fruits subjected to postharvest treatments. In the field, besides the management adopted by the farmer, seven products were sprayed three times during fruiting for evaluation. Postharvest products were diluted in water or in oxidized polyethylene wax and shellac. Water treatments with potassium phosphite, Soil-Set®, chlorine dioxide, thyme essential oil, sodium bicarbonate, lemon grass essential oil and thiabendazole reduced the incidence of diseased fruits, and anthracnose, the main disease, was controlled with sodium bicarbonate, lemon grass essential oil and thiabendazole. Greater soluble solids content was found for control (water), chlorine dioxide, acibenzolar-S-methyl and thiabendazole. For the products that reduced anthracnose, there was no correlation between the disease and the physicochemical parameters, evidencing that the disease control is not associated with delayed ripening. For wax treatments, diseases were not controlled, and the fruits presented lower titratable acidity with thyme essential oil, sodium bicarbonate, control (wax), acibenzolar-S-methyl and lemon grass essential oil. Control and thyme essential oil were highlighted for maintaining the green coloration of the fruit skin for the shortest period. Under field conditions, azoxystrobin, thiabendazole, difenoconazole+azoxystrobin and acibenzolar-S-methyl+azoxystrobin reduced the occurrence of diseased fruits, while anthracnose control was only obtained with azoxystrobin.

Highlights

Avocado varieties commercially grown in Brazil can be grouped into exportation or domestic consumption types
The products azoxystrobin, thiabendazole, difenoconazole+azoxystrobin and acibenzolar-S-methyl+azoxystrobin, when added to the treatment already adopted by the farmer, reduced by 13.3 to 26.4% the number of fruits showing rot symptoms, while anthracnose control was only obtained with azoxystrobin, which led to a reduction of 34.4% in the incidence, relative to control
The fungicides registered in Brazil for anthracnose control in avocado trees are the copper fungicides copper oxychloride and cuprous oxide, the mixture mancozeb+copper oxychloride and the systemic fungicides difenoconazole and thiabendazole; the latter can be applied in the field and in the postharvest (BRASIL, 2017)

Summary

Introduction

Avocado varieties commercially grown in Brazil can be grouped into exportation or domestic consumption types. Those preferred for domestic consumption generally have bigger fruits with low oil content. ‘Hass’ avocado production has increased in the last years, being especially destined for the European market. The fruit of this variety presents oval to pyriform shape and average mass between 180 and 300 grams; its thick and rough skin is green before and immediately after harvest but changes to dark brown when ripe (SCHAFFER et al, 2013). Wax application improves the appearance of fruits and extends their conservation by diminishing both the transpiration rate and the metabolic activity (DARVAS et al, 1990)

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Results