Effects of Two Fungicides, Caocobre and Ridomil on the Rhizosphere Microflora of Cocoa (Theobroma Cacao L) Seedlings

The effect of two fungicides, Caocobre and Ridomil on rhizosphere phenomenon of Cocoa (Theobroma cacao L) seedlings has been studied at different stages of the development of the plant growing in pots. Fungal population in the rhizophere soil was generally higher than in the non-rhizosphere soil. The total number of fungal population in both the rhizosphere and non-rhizosphere was highest on the 28 day and thereafter declined. The effect of the fungicides on the mycoflora differed from species to species with no clear cut generalized response. Members of the genera Aspergillus and Penicillium predominated over the other genera encountered namely Cladosporium, Trichoderma, Fusarium, Paecilomyces and Neurospora. In the control seedlings, five Aspergillus species were isolated, namely Aspergillus niger, A. flavus, A. ochraceus, A. sulphureus, and A. fumigatus; four Penicillium species were also isolated, Penicillium digitatum, P. expansum, Penicillium sp. (white) and P. verrucosum var cyclopium. Other species isolated were Trichoderma viride, Paecilomyces varioti, Cladosporium herbarum and Rhizopus oryzae. When Cacaobre was applied repeatedly the following fungal species were encountered in the rhizosphere region of the soil: A. niger, A. flavus, A. ochraceus (after 28 days only) P. digitatum, P. verrucosum var cyclopium, Fusarium sp., T. Viride, Paecilomyces varioti, Cladosporium herbarum and Rhizopus sp. Ridomil application showed similar trend.