Author : Phikun Nuchnuanrat

Summary : Colletotrichum musae, Fusarium sp. and Lasiodiplodia theobromae were isolated and identified as crown rot pathogens associated with banana 'Kluai Hom Thong' in Chantaburi, Chonburi and Rayong provinces, Thailand. Preliminary screening methods for efficacy test of ethanol crude extract from 22 plants were tested in vitro. Eugenia caryophyllus, Cinnamomum zeylanicum and Impatients balsamina at 10,000 ppm showed complete inhibition in mycelial growth and spore germination of all three fungi. In vitro evaluation showed that percent inhibition was directly correlated with the concentration of plant extract. Effective concentrations to inhibit mycelial growth and spore germination of three fungi were E. caryophyllus extract at 1,000-10,000 ppm, C.zeylanicum and Impatients balsamina extract at 10,000 ppm. However, L. theobromae was tolerant to I. balsamina with mycelial inhibition of 45.99% while it inhibited mycelial growth of C. musae and Fusarium spp. at 5,000-10,000 ppm. Application of the plant extract 5h after inoculation was more effective in controlling the disease than applied 24 h before inoculation as protectant. ANy plant extract treatment alone at 50,000 ppm gave less than 50% crown rot disease reduction on banana. Eugenia caryophyllus extract at 12,500 ppm C. zeylanicum extract at 25,000 ppm or I. balsamina extract at 25,000 ppm combined with hot water at 40 deg C for 10 min were effective in reducing crown rot and did not influence the quality of banana fruit. All plant extracts were shown to have inhibition active compounds against the crown rot fungi based on thin layer chromatography bioautographic result. The Eugenia caryophyllus extract showed a very clear inhibition against C. musae and Fusarium sp. Cinnamomun zeylanicum and I. balsamina extracts did not produce clear inhibition to fungi after TLC bioautography which means that the extract may possibly contain only small amounts of active constituents.