Etude d'antagonistes naturels a Phytophthora palmivora dans la region cotiere de Kribi au Cameroun
In the coastal region of Kribi, an ant is found which was introduced into the Cameroun and spread by man: Wasmannia auropuncta Roger. Since this ant attacks certain enemies of cocoa, its influence on the production of cacao has been studied. From statistics, it was possible to show, contrary to expectation, a lessening of the rate of black pod (Phytophthora palmivora) in over run plantations. New studies have shown that this lessening seemed only to appear when mealy bugs often associated with this ant were present, mainly Planococcoides njalensis Laing (sensu lato) and Stictococcus intermedius News. It was attempted to obtain reliable evidence of the antagonistic effect of mealy bugs on Phytophthora palmivora first, in natural conditions by artificially infecting pods inhabited by these insects, and then in the laboratory by the study of the bacterial population associated with these insects. In experimental infection in the field in the successful percentage of infections shown, the presence of Pseudococcids was the lowest. With Stictococcides, it was higher and identical with the controls (infected pods free of mealy bugs). In the laboratory, bacterial isolates, obtained by direct inoculation into the middle of the culture or by inoculation with crushed insects, have shown a competitive effect against Phytophthora palmivora. An inhibitory effect on the growth of Phytophthora palmivora has been found with two of these bacterial isolates, but the effect is weak, which might be due to the difficulty of cultivating both bacteria and fungi on the same medium. We propose in the future to give up mixed cultures and to incorporate filtrates of the bacterial cultures in a medium suitable to Phytophthora palmivora. It must be pointed out that we have not established the presence of Pseudomonas aeruginosa, recognised in Ghana as an antagonist of Phytophthora palmivora or isolated it from mealy bugs
| Main Authors: | , , , , , , , , , |
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| Format: | biblioteca |
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St. Augustine (Trinidad y Tobago)
1972
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| Subjects: | THEOBROMA CACAO, PHYTOPHTHORA, PODREDUMBRES, ENFERMEDADES FUNGOSAS, ANTAGONISMO, COMPETENCIA BIOLOGICA, WASMANNIA AUROPUNCTATA, STICTOCOCCUS INTERMEDIUS, PSEUDOMONAS AERUGINOSA, PLANOCOCCOIDES NJALENSIS, CAMERUN, |
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| Summary: | In the coastal region of Kribi, an ant is found which was introduced into the Cameroun and spread by man: Wasmannia auropuncta Roger. Since this ant attacks certain enemies of cocoa, its influence on the production of cacao has been studied. From statistics, it was possible to show, contrary to expectation, a lessening of the rate of black pod (Phytophthora palmivora) in over run plantations. New studies have shown that this lessening seemed only to appear when mealy bugs often associated with this ant were present, mainly Planococcoides njalensis Laing (sensu lato) and Stictococcus intermedius News. It was attempted to obtain reliable evidence of the antagonistic effect of mealy bugs on Phytophthora palmivora first, in natural conditions by artificially infecting pods inhabited by these insects, and then in the laboratory by the study of the bacterial population associated with these insects. In experimental infection in the field in the successful percentage of infections shown, the presence of Pseudococcids was the lowest. With Stictococcides, it was higher and identical with the controls (infected pods free of mealy bugs). In the laboratory, bacterial isolates, obtained by direct inoculation into the middle of the culture or by inoculation with crushed insects, have shown a competitive effect against Phytophthora palmivora. An inhibitory effect on the growth of Phytophthora palmivora has been found with two of these bacterial isolates, but the effect is weak, which might be due to the difficulty of cultivating both bacteria and fungi on the same medium. We propose in the future to give up mixed cultures and to incorporate filtrates of the bacterial cultures in a medium suitable to Phytophthora palmivora. It must be pointed out that we have not established the presence of Pseudomonas aeruginosa, recognised in Ghana as an antagonist of Phytophthora palmivora or isolated it from mealy bugs |
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