Normal view MARC view ISBD view

La double orientation necessaire des études concernant la lutte contre la pourriture brune des cabosses du cacaoyer (Phytophthora palmivora): quelques aspects de ces études

by Muller, R.A; Cocoa Research Institute, Tafo (Ghana); 3. International Cocoa Research Conference Accra (Ghana) 23-29 Nov 1969.
Publisher: Tafo (Ghana) 1971Description: p. 405-409.Other Title: Proceedings.Subject(s): CONTROL CULTURAL | CONTROL QUIMICO | ENFERMEDADES FUNGOSAS | PHYTOPHTHORA PALMIVORA | PODREDUMBRES | PROFILAXIS QUIMICA | RESISTENCIA A LA ENFERMEDAD | THEOBROMA CACAO | CHEMICAL CONTROL | CHEMOPROPHYLAXIS | CULTURAL CONTROL | DISEASE RESISTANCE | FUNGAL DISEASES | PHYTOPHTHORA PALMIVORA | ROTS | THEOBROMA CACAO | CHIMIOPREVENTION | LUTTE CHIMIQUE | LUTTE CULTURALE | MALADIE FONGIQUE | PHYTOPHTHORA PALMIVORA | POURRITURE | RESISTANCE AUX MALADIES | THEOBROMA CACAOSummary: The fight against the black pod disease of cocoa can be by direct intervention (chemical treatments through prophylactic and agronomic measures) or by the use of cocoa varieties which are resistant or tolerant to the disease. The second formula is certainly the more enticing, and makes it possible to expect a definite solution to the problem, while the first implies a continual effort on the part of the producer. In a given region, it is the local importance of the disease which dictates the choice of methods, and consequently the orientation to be given to the studies. In countries where little infection occurs, as for example, in the Ivory Coast where it was quickly proved that the cost of treatments was greater than the cost of damage caused by the disease, it has been possible, naturally, to overlook studies of direct control methods and devote the time calmly to long-term research into resistant varieties. In countries of heavy infection, such as the Cameroon where damages are calculated at an average of 50 per cent of the total production, the commencement of chemical treatments, unlike the former case, has had to be the prime objective of research work for the protection of the production potential; on reaching this point, the main effort can henceforth be to deal with research into resistant varieties, but positive results in this direction can only be reckoned with in the long term. The perfection of methods of direct control should not be overlooked. Study of the sensitivity of cocoa and research into resistant varieties, and study of techniques of direct intervention must therefore be considered at the same time in areas where the disease is particularly serious. Besides, it is worth noting - and this wighs more in favour of the need for direct control - that the grouping of countries into "heavily" or "lightly" affected, may have a temporary value only. It could be imagined, indeed, that such and such a country is lightly affected simply because of genetic or agronomic improvement in production: there exists, in effect, a positive correlation between production and the rate of infection. The possibility of alterations in the pathogen whose virulence can be marked or whose character can be changed is liable, on the other hand, to give the selections a less definite or more incomplete character. Study of the sensitivity of cocoa and research into resistant varieties are desirable on the following points which sometimes raise fundamental questions all of which concern problems of methods: (a) Study, by inoculation tests, of the tolerance of the varieties or types of cocoa trees in existence in the area, in relation to attacks by Phytophthora palmivora. (b) Study of the mechanisms of hereditary transmissions of resistance and tolerance. (c) Study of anatomical, physiological and biochemical factors of tolerance and resistance. (d) Studies of variations in tolerance of the same types or varieties of cocoa trees in different ecological areas in relation to the strains of the pathogen in these areas. (c) Biological study of several strains of Phytophthora palmivora and study of their pathological variability (on the plan of their pathogenic power). The study of the techniques of direct intervention raises principally problems of experimental methodology, as concerns the heterogeneity of the surroundings. Some work has been done in the attempt to solve these problems so as to allow for quick and accurate tests on the efficiency of new fungicides. The orientation to be given to the studies should be related to the perfection of methods of application of fungicides, research into new fungicides with better control than the copper fungicides (systemic or simple impregnators of the cuticles). The toxicity of these fungicides should be studied from the point of view of their influence on the fermentation of the product, and toxicity to man. In conclusion, if the sensitivity studies of the cocoa trees and research into resistant varieties should be made the centre of attention and the object of profound studies, those studies aimed at improving the conditions of direct control in the countries where it should be adopted, must be actively pursued. These studies are complementary, the same way as the results which they may produce - less sensitive varieties, better protection by simplified or more effective treatments
    average rating: 0.0 (0 votes)
No physical items for this record

Sum. (En)

The fight against the black pod disease of cocoa can be by direct intervention (chemical treatments through prophylactic and agronomic measures) or by the use of cocoa varieties which are resistant or tolerant to the disease. The second formula is certainly the more enticing, and makes it possible to expect a definite solution to the problem, while the first implies a continual effort on the part of the producer. In a given region, it is the local importance of the disease which dictates the choice of methods, and consequently the orientation to be given to the studies. In countries where little infection occurs, as for example, in the Ivory Coast where it was quickly proved that the cost of treatments was greater than the cost of damage caused by the disease, it has been possible, naturally, to overlook studies of direct control methods and devote the time calmly to long-term research into resistant varieties. In countries of heavy infection, such as the Cameroon where damages are calculated at an average of 50 per cent of the total production, the commencement of chemical treatments, unlike the former case, has had to be the prime objective of research work for the protection of the production potential; on reaching this point, the main effort can henceforth be to deal with research into resistant varieties, but positive results in this direction can only be reckoned with in the long term. The perfection of methods of direct control should not be overlooked. Study of the sensitivity of cocoa and research into resistant varieties, and study of techniques of direct intervention must therefore be considered at the same time in areas where the disease is particularly serious. Besides, it is worth noting - and this wighs more in favour of the need for direct control - that the grouping of countries into "heavily" or "lightly" affected, may have a temporary value only. It could be imagined, indeed, that such and such a country is lightly affected simply because of genetic or agronomic improvement in production: there exists, in effect, a positive correlation between production and the rate of infection. The possibility of alterations in the pathogen whose virulence can be marked or whose character can be changed is liable, on the other hand, to give the selections a less definite or more incomplete character. Study of the sensitivity of cocoa and research into resistant varieties are desirable on the following points which sometimes raise fundamental questions all of which concern problems of methods: (a) Study, by inoculation tests, of the tolerance of the varieties or types of cocoa trees in existence in the area, in relation to attacks by Phytophthora palmivora. (b) Study of the mechanisms of hereditary transmissions of resistance and tolerance. (c) Study of anatomical, physiological and biochemical factors of tolerance and resistance. (d) Studies of variations in tolerance of the same types or varieties of cocoa trees in different ecological areas in relation to the strains of the pathogen in these areas. (c) Biological study of several strains of Phytophthora palmivora and study of their pathological variability (on the plan of their pathogenic power). The study of the techniques of direct intervention raises principally problems of experimental methodology, as concerns the heterogeneity of the surroundings. Some work has been done in the attempt to solve these problems so as to allow for quick and accurate tests on the efficiency of new fungicides. The orientation to be given to the studies should be related to the perfection of methods of application of fungicides, research into new fungicides with better control than the copper fungicides (systemic or simple impregnators of the cuticles). The toxicity of these fungicides should be studied from the point of view of their influence on the fermentation of the product, and toxicity to man. In conclusion, if the sensitivity studies of the cocoa trees and research into resistant varieties should be made the centre of attention and the object of profound studies, those studies aimed at improving the conditions of direct control in the countries where it should be adopted, must be actively pursued. These studies are complementary, the same way as the results which they may produce - less sensitive varieties, better protection by simplified or more effective treatments

Click on an image to view it in the image viewer