Cacao canker in Java
Cacao canker is a red rot of the outer bark, which reaches the cambium only on the most susceptible trees. Its most rapid spread is tangential in the outer, and longitudinal in the inner, bark. Phytophthora faberi, which causes the disease, is difficult to isolate directly except from rapidly spreading lesions. It can be more easily obtained by using marginal canker tissue as crude inoculum in controlled wound inoculations on immature cacao pods; from the successfully inoculated pods the fungus is easily isolated. By removing the bark from cambium-killing lesions, sporulation can be induced on the underlying wood. In most countries the Phytophthora infections are reported more numerous in the pods than in the bark; in Java, on the other hand, cankers are often more numerous than rotten pods. Phytophthoras obtained from cacao differ decidedly from each other both morphologically and physiologically. The promiscuous cutting out of lesions appears to do more harm than good in Java, and the superficial shaving of lesions recommended by a number of writers is of very dubious value. The great variation in resitance of cacao to canker appears to be the key to the decrease of the damage from this disease.
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| Format: | biblioteca |
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1925
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| Subjects: | THEOBROMA CACAO, PHYTOPHTHORA FABERI, ENFERMEDADES FUNGOSAS, INOCULACION, ESPORULACION, AISLAMIENTOS, JAVA, |
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| Summary: | Cacao canker is a red rot of the outer bark, which reaches the cambium only on the most susceptible trees. Its most rapid spread is tangential in the outer, and longitudinal in the inner, bark. Phytophthora faberi, which causes the disease, is difficult to isolate directly except from rapidly spreading lesions. It can be more easily obtained by using marginal canker tissue as crude inoculum in controlled wound inoculations on immature cacao pods; from the successfully inoculated pods the fungus is easily isolated. By removing the bark from cambium-killing lesions, sporulation can be induced on the underlying wood. In most countries the Phytophthora infections are reported more numerous in the pods than in the bark; in Java, on the other hand, cankers are often more numerous than rotten pods. Phytophthoras obtained from cacao differ decidedly from each other both morphologically and physiologically. The promiscuous cutting out of lesions appears to do more harm than good in Java, and the superficial shaving of lesions recommended by a number of writers is of very dubious value. The great variation in resitance of cacao to canker appears to be the key to the decrease of the damage from this disease. |
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