Journal of Applied Biosciences (J. Appl. Biosci.) [ISSN 1997 - 5902]
Volume 20: 1183 - 1193. Published August 7, 2009.
Effects of climatic parameters on the expression of the black pod disease on Theobroma cacao in Côte d’Ivoire
Mpika Joseph*,*****^, Auguste Emmanuel Issali**, Ismaël Boubacar Kébé*, Brou Kouamé***, Jean Louis Konan**, Kouassi Allou**, Nicodême A. Zakra****, Severin Aké *****
* Laboratoire de Phytopathologie, Centre National de Recherche Agronomique (CNRA). BP 808 Divo, Côte d’Ivoire ;**Laboratoires de Génétique et de phytopathologie, Station de Recherche sur le Cocotier Port Bouët Marc Delorme, CNRA, 07 BP 13 Abidjan 07, Côte d’Ivoire ; *** Direction des Programmes de Recherche et de l’Appui au Développement (DPRAD), CNRA, 01 BP 1740 Abidjan 01, Côte d’Ivoire ; **** Laboratoire Central Sols, Plantes et Eaux, CNRA, BP 602 Gagnoa, Côte d’Ivoire ; ***** Laboratoire de Physiologie végétale, UFR de Biosciences, Université de Cocody, 22 BP 582 Abidjan- Côte d’Ivoire.
^Corresponding author email; Jmpika@yahoo.fr ; Tel: (+225) 05.43.80.41
ABSTRACT
Objectives: To determine variation in black pod disease that is explainable by the climate and evaluate the changes in sensitivity of Phytophthora palmivora to Trichoderma species as influenced by variations in climatic parameters.
Methodology and results: The effects of 6 climatic parameters were evaluated. Four different zoospores’ suspensions as bio fungicides constituting the treatments T1 as Trichoderma spirale, T2 as Trichoderma harzianum, T3 as Trichoderma virens and T4 as Trichoderma asperellum were assessed. Untreated (T5) was included as control. These 4 treatments were applied each on 100 cocoa trees according to Despreaux’s random targets method. The rainfall, maximal and minimum temperature, relative humidity, mean temperature and temperature gaps as climatic parameters were recorded daily from June to February in the course of the years 2006-2007 and 2007-2008. The separation of means and Principal Component Analysis were used to determine the best climatic parameters disease occurrence. Non-linear polynomial multiple regression was used to quantify the link between intensity of the black pod disease and the climatic parameters through R2-value. Due to their weak annual variations, maximal temperature, temperature gaps and relative humidity were eliminated. From the first to the second year, rainfall, minimal and mean temperatures explained 55.90 and 61.70%, respectively, of the black pod disease fluctuations in the untreated control. However, in the presence of 4 Trichoderm species, the fluctuations of black pod disease caused by P. palmivora varied from 12.10 to 39.60%, respectively, in the first and second year.
Conclusion and application of findings: Climate significantly influences black pod disease development. T. asperellum which proved to be the best will be used in large fields trials.
Key words: disease variation, sensitivity to climatic variations, biofungicides, random targets method.
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