Inoculum Concentration of Armillaria mellea in the Rhizosphere of Intercropped Teak Plantation: the case of the Opro Forest Reserve, Ghana

Abstract

Teak (Tectona grandis Linn. F.) is the most planted timber tree species in Ghana, with over 73,916 hectares of plantation established at the end of 2008. Many of the teak plantations established in the semi-deciduous forest zones were done using the taungya system with various intercrops. Symptoms of Armillaria (Vahl: Fr.) root-rot of teak have been reported in the taungya plantations, especially in the semi-deciduous forest zones. The study aimed to determine inoculum concentrations of Armillaria mellea in the rhizosphere soil of intercropped teak and compare with sole teak plantation. Mycoflora were isolated from rhizosphere soil of teak intercropped with pepper, okra, maize, yam or cassava at year one to year three sapling stage. Dilution plate technique was used for mycoflora isolation and dilution factor of 10-3 was inoculated on potato dextrose agar amended with chloramphenicol (25mg/l) and incubated at 280C for 14 days after which A. mellea colonies were identified and counted. More A. mellea (Vahl: Fr.) colonies were isolated from rhizosphere soils of intercropped teak plantations than non-intercropped. Differences in A. mellea colonies were more significant amongst intercrops than amongst age of teak plantation at (P ≤ 0.05). There were significantly (P ≤ 0.05) higher numbers of A. mellea colonies in rhizosphere soils of teak intercropped with cassava compared with other intercrops. Number of A. mellea colonies in rhizosphere soils of intercropped teak did not have linear relation with age of teak plantation. Intercropping could promote Armillaria root rot of teak especially with cassava as intercrop.