EVALUATION OF LEAF EXTRACTS OF FIVE PLANT SPECIES AGAINST RED ROT PATHOGEN OF SUGARCANE (Saccharum officinarum).

Abstract

The research was carried out to evaluate the in vitro effects of five botanicals extracts, Argomone mexicana, Hyptis suaveolens, Corchurus olitorius Cymbopogon citratus and Acalypha wilkesiana on mycelial growth of colletotrichum falcatum, the pathogen of red rot disease of sugarcane with methanol and aqueous extratants, at concentrations of 150mg/ml, 200mg/ml and 250mg/ml using food poison techniques. The results on phytochemical analysis revealed that these botanicals contained alkaloids, saponins, glycosides, flavonoids and steroids. At 250mg/ml concentration of methanol extracts, 100% inhibition in mycelial growth were recorded in both C. citratus and C. olitorius which were significantly different (P<0.05) from other botanicals; A. wilkesiana (88.72%) and H. suaveolens (82.56%). The least inhibition (47.68%) was recorded in A. mexican. In aqueous extracts, at 250mg/ml concentration, 41.87% mycelial growth inhibition of C. falcatum was recorded in C. citratus, followed by A. wilkesiana (24.42%) and least inhibition in H. suaveolens (15.66%6), while C. olitorus and A, mexicana has no effect. Also the inhibition increased significantly with increase in concentrations from 150mg/ml to 250mg/ml of the botanicals in either of both extractants. In comparing the efficacy of the two solvents (methanol and aqueous) used in the study, it was observed that methanol extracts at different concentrations inhibited the mycelial growth of C. falcatum better than the aqueous. However, in all, C. citratus gave maximum inhibition which was statistically different (P<0.05) from other botanicals. On this note, these botanicals are recommended for the field trial on the control of red rot disease of sugarcane.