Browsing by Author "Ducamp, M."

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    Impact of environmental factors, chemical fungicide and biological control on cacao pod production dynamics and black pod disease (Phytophthora megakarya) in Cameroon
    (2008) Tondje, P.R.; Deberdt, P.; Mfegue, C.V.; Bon, M.C.; Ducamp, M.; Ndoumbe-Nkeng, M.; Hurard, C.; Begoude, B.A.D.; Hebbar, P.K.; Cilas, C.
    The impact of environmental factors and microbial and chemical control methods on cacao pod production dynamics and spread of black pod disease caused by Phytophthora megakarya was assessed over three consecutive years in a smallholder’s plantation. Significant positive correlations were found between rainfall records and pod rot incidence when assessed after a 1-week lag. Disease distribution across various pod developmental stages showed that immature pods were the most susceptible to P. megakarya attack. Weekly observations of the pod distribution and disease progression at various developmental stages on cacao trees sprayed with fungicide Ridomil, Trichoderma asperellum biocontrol agent (strain PR11), or untreated control trees indicated that the total pod production and the incidence of black pod rot was significantly different between the treatments. The disease rates were 1.73%, 47.1% and 71.23% in the plots treated with fungicide, PR11 and untreated, respectively, in 2004, and 0.67%, 11.35% and 34.04% in the same plots in 2005. A significant carry over effect of the biological agent was noticed up to 1 year after the sprays with strain PR11 were halted. The disease incidence averaged 16.67% in the plots previously sprayed with PR11 and 35.88% in the control plot, although both the plots were sprayed with the same contact fungicide, Kocide. Monitoring through enumeration and molecular typing revealed that Trichoderma propagules remained consistently more abundant in flower cushions of cacao trees than in soil or bark. This study showed that microbial control of black pod disease with PR11 was promising but not as effective as the chemical methods under the current high disease pressure, and therefore needs to be integrated with other control methods to establish a sustainable management system for black pod disease in Cameroon.
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    New sources of resistance to Phytophthora megakarya identified in wild cocoa tree populations of French Guiana
    (2008) Paulin, D.; Ducamp, M.; Lachenaud, P.
    Cocoa black pod rot. a disease caused by oomycetes of the genus Phytophthora, causes substantial yield losses throughout the world. particularly in Africa with the very aggressive species Phytophthora megakarya. In order to reduce the impact of that pathogen, priority ie given to genetic control through more resistant cultivars, and breeders are seeking sources of resistance in wild cocoa trees. Wild cocoa trees were surveyed in French Guiana between 1985 and 1995, leading to the collection of abundant plant material from more than 200 mother trees originating from five river basins. We present here the results of tests to assess resistance to the species P. megakarya (a species only existing in Africa), conducted at CIRAD in Montpellier. France, on circa 40 genotypes collected in the Camopi river basin, along with approximately 20 genotypes from other populations (Kerindioutou, Borne 7, Euleupousing, Pina and Oyapok). The strain used for artificial inoculation was NS269. isolated in Cameroon. Seven cacao clones were classified as "highly resistant" and 29 as "resistant", some of which displayed greater resistance to P. megakarya than the reference resistant clone IMC 47, This study suggests that the wild material from Preach Guiana could play a significant role in controlling P. megakarya in Africa and also Phytophthora palmivora in all cocoa-producing zones.
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