Control of Lasiodiplodia theobromae (PAT) on Rhizophora racemosa using plants extracts

Abstract

Laboratory experiments were conducted to ascertain fungal isolates of Rhizophora racemosa .Studies on controlling L. theobromae using plant extracts was also carried out. Fungal pathogens were isolated by cutting the infected portions of the leaves and aseptically placing in glass Petridish for 7 days. Pathogenicity test was done in-situ with spore suspension inoculated on Rhizophora racemosa seedling leaves and observed for 15 days in the green house. Different concentrations ranging from (20%, 40%, 60%, 80% and 100%) of extract derived from the bark of Rhizophora racemosa, leaves of Aloe vera and Jatropha curcas were tested on the isolated fungi. The results showed that Lasidiplodia theobromae, Penicillium citrinum, Aspergillus niger and Paecilomyces lilacinus were isolated from the leaves of Rhizophora racemosa. Pathogenicity test revealed that Lasidiplodia theobromae was pathogenic on Rhizophora racemosa. Aloe vera and the bark of Rhizophora racemosa were inhibitory at 100% on Lasidiplodia theobromae (0.1645g and 0.2946g mycelial dry weight respectively). Jatropha curcas had les inhibitory effect at 80% concentration on the tested fungus (0.9118g mycelial dry weight). Biochemical test showed that Quinone, terpenoid and saponin from Aloe vera, bark of Rhizophora racemosa and Jatropha curcas respectively were suspected to account for the inhibition of the tested fungus (Lasidiplodia theobromae).