Evaluation of antifungal activity of some invasive alien species plant extracts against coffee berry disease (Colletotrichum kahawae Bridge and Waller) in Ethiopia

Abstract

Coffee is one of the most important trade commodities in the world next to petroleum. Arabica coffee (Coffea arabica L.) is the world most important commercial coffee species. Coffee berry disease (CBD) caused by Colletotrichum kahawae is the major threat to Arabica coffee production in Ethiopia and the world. The use of fungicides against the disease has shown to induce negative effect on environment and result in the appearance of fungicide resistant pathogen biotype. It is also expensive for farmers in countries like Ethiopia. Thus it is important to look for alternative management strategies of the disease. This study aimed at evaluating the antifungal activities of aquous, ethanol and acetone extracts of five different invasive alien species in vitro against C. kahawae mycelia growth. Then we tested two of the best performed invasive plant extracts on detached green berries and seedlings in vivo against disease development applying the extracts at 3 different times of application (at the time of inoculation, 48 hrs before inoculation and 48hrs after inoculation) of the pathogen, in completely randomized design with three replications. The extracts were from Parthenium hysterophorus, Lantana camara, Prosopis juliflora, Eichhornia crassipes and Mimosa diplotricha. All the crude extracts showed in vitro antifungal activity at 20 %( w/v). The study indicated that the inhibitory effect of the extracts depends on the type of plant species used, solvent type and time of application of the extracts. Generally, L.camara and P.juliflora ethanol and acetone extracts significantly reduced radial growth of the pathogen compared to the control. L.camara reduced radial growth of the pathogen with 76.23 and 84.3%, and P.juliflora with 62.63 and 66.96% in 70% ethanol and acetone respectively. Furthermore, L.camara ethanol and acetone extracts reduced disease severity on detached green berries to 20 and 29.1% when applied before inoculation of the pathogen. Likewise, ethanol and acetone extract of L. camara applied before innoculation highly inhibited the effect of the pathogen,and shows highly significant difference as compared to the untreated control in vivo. The study indicated the possible use of extracts of L.camara as an alternative means of CBD management but further study at field conditions should be carried out to verify the result.