Estudios sobre la podredumbre de la fruta del cacao causada por Phytophthora en Costa Rica

Abstract

Pod rot of cacao induced by Phytophthora palmivora Butl. causes heavy losses in Costa Rica. Average losses of part of 1953 were 47 percent at La Lola experimental farm of the Inter-American Institute of Agricultural Sciences. Investigations on this disease are devoted to three problems, namely, disease development, disease resistance, and disease control. The mode of infection of flowers, flowering cushions, pods, stems and leaves of cacao by P. palmivora were studied previously and were published. Experiments are in progress to find a mrthod that would permit detection of disease resistance in cacao. Pods are being used. Resistance in relation to pod pigmentation is also studied. Two lines of investigation are in progress on fungicidal control of pod rot of cacao, one on screening of new fungicides, and the other on practical field application of the best fungicides found in the screening tests. Four experiments on fungicidal control are now in progress in Costa Rica. In the first are included Bordeaux mixture applied at 30 and 60 day intervals, SR-406, SR-50, applied every 30 days, and Dithane Z-78 applied every 30 days. Results of the first and second years showed that Bordeaux mixture was more effective than the other treatments in reducing infection, but no significant difference was found in yield due to the treatments. Results of 1952-53 showed that Bordeaux mixture and Dithane Z-78 applied every 30 days increased yield in comparison to the other treatments. The increase in yield brought about by Dithane Z-78 might have been due to the presence of zinc in the fungicide. Results of the second experiment indicate that Dithane Z-78 applied every 7 and 14 days is almost as effective as Bordeaux mixture at 30 day intervals. In the third experiment are included Bordeaux mixture, Perenox, Crag-531 and Phygon-XL, and in the fourth experiment a study is being made of spray schedules. Fungicides are available which are in themselves as effective as Bordeaux mixture but none of those tested, with the exception of perenox, has the residual capacity of this mixtures.