ABSTRACT


Erna M. Soto A.1, Adriana Pinto de Torres2 y Lautaro Cancino E.3
 
In order to evaluate the effect of new fungicides and to identity the causal organisms of post-harvest diseases of table grapes, Almería and Emperor varieties, this trial was carried out under field conditions in the Chiñigue area, near Santiago. The laboratory test were done at "La Platina" Experiment Station of the Instituto de Investigaciones Agropecuarias. The material used in the control of grape disease were: Cercobin M. 70% WP (Thiophanate) 60 g/100 liters, Benlate 50% WP (Benomyl) 60 g/100 l., Tecto 60% WP (TBZ) 300 g/100 l., and some nonsystemic fungicides like Sclex 30% WP (dichlozoline) 200 g/100 l. and a mixture of Orthocide 50% WP (Captan) 7 Kg/ha and sulfur 28 Kg/ha, complemented with SO2 fumigation. The latter mixture was applied as a dust; the other fungicides were applied as sprays.In general, the fungicides were sprayed 18 and 3 days before harvest, except themixture of Orthocide plus sulfur that was applied only 8 days before harvesting.All the samples were spray-inoculated with a suspension of Botrytis cinerea (conidiaand mycelium) after harvest and then storfd under reftigerated conditions. Twosamples taken from untreated fruit, one inoculated and other noninoculated, wereused as checks.The degree of control provided by the fungicides was estimated by determiningthe porcentage of rotten fruits. This was done after 26 and 61 days of cold storage.All the samples were maintained 6 days under simulated market conditions before theevaluation.According to the results, the best control was provided by Orthocide 50 with sulfurand SO2 fumigation. No statistical differences were obtained among Benlate, CercobinM. and Tecto 60. The effect of Benlate was statistically superior to Sclex.Different kinds of decays in the fruit were observed aL the end of the experiment.The various types of decay according to their characteristics were classified in thefollowing groups: a) Botrytis rot; b) Penicillium rot; c) black rot, and d) mixed rot.The following microorganisms were isolated from diseased tissues and. rankedaccording to their frecuency of occurrence in the fruit examined:1) Botrytis cinerea Pers. ex Fr.; 2) Alternaría alternata (Fr.) Keissler; 3) Penicilliurnexpansum (Lk.) Thom; 4) Cladosporium herbarum (Pers.) Lk. ex Fr.; 5) Ulocladiurnatrum Preuss; 6) Stemphyliurn botryosum Wallr.; 7) Penicillium wortmanniKlocker; 8) Epicoccurn purpurascens Erhb. ex Schlecht.; 9) Aspergillus niger vanTiegh.; 10) Gliocladium roseum. (Lk.) Bainier; 11) Cladosporiurn cladosporioides (Fr.) De Vries; 12) Mucor racemosus Fresenius; 13) Botrytis sp.; 14) Fusariurn roseum(Lk.) Snyder and Hansen; 15) Fusarium axysporum, and 16) Trichotheciurn roseum Lk. ex Fries.In order to study the pathogenicity of each fungus, artificially wounded fruit and normal fruit were inoculated and held under refrigeration (0 - 1°C) and at roomtemperature (18 - 20°C).Under 0-1°C, the fungi: 1), 2), 3), 4) and 13) caused rofs in both normal andwounded fruit. The fungus U. atrum was pathogenic in Almería normal fruit and alsoproduced mycelium in Emperor grapes 35 days after inoculation. Cladosporium cladosporioides caused darnage only in Emperor fruit. The species F. pxysporumand S. botryosum produced scarce mycelia in normal fruit. Aspergillus niger and T. roseumdid not cause infection under these conditions.All the organisms isolated attacked wounded fruif at market temperature (18 - 20°C),but only the fungi numbered 1) to 7), 9), 10), 11), 12), 13), 15) and 16) causedinfection of normal fruit of both varieties. Under the same conditions in the Emperorvariety, the species E.purpurascensbehaved as a real pathogen and the fungiG. roseum and F. roseum produced scarce mycelia 35 days after inoculation.The fungi isolated in this research have not been mentioned before as pathogens ofgrapes in Chile, with the exception of Botrytis cinerea and Cladosporium herbarum,reported by Mujica and Vergara in 1945.
Key words:
1Ing. Agr., Servicio Agrícola y Gandero, Curicó.
2Ing. Agr., Investigador INIA, Casilla 5427, Santiago, Chile. Profesor Cátedra de Patología Frutal, Facultad de Agronomía, Universidad de Chile.
3Ing. Agr., Investigador Estación Agronómia Antumapu, Profesor Coordinador Cátedra Patología Frutal, Facultad de Agronomía, Universidad de Chile.