Screening of weed extracts for antifungal properties against Colletotrichum lagenarium, the causal agent of anthracnose in cucumber

The antifungal activity of the leaf extracts from 203 weed species was investigated by performing a bioassay using cucumber plants and Colletotrichum orbiculare. The leaf extracts from four families, namely, Urticaceae, Onagraceae, Commelinaceae, and Solanaceae, showed a relatively stronger inhibition of the anthracnose lesions in cucumber plants when compared with the other families investigated in the study. A remarkable inhibition of anthracnose infection in cucumber leaves was observed with the extracts from the following 19 weed species: Boehmeria nipononivea and Boehmeria longispica, Persicaria scabra, Ranunculus japonicus and Ranunculus sceleratus, Cardamine flexuosa, Oenothera biennis, Aeschynomene indica, Indigofera pseudo-tinctoria, Torilis scabra, Calystegia japonica, Solanum americanum, Bidens pilosa, Gnaphalium japonicum, Kalimeris yomena, Bromus catharticus, Cynodon dactylon, Alopecurus aequalis, and Scirpus tabernaemontani. In particular, it is noteworthy that the extracts from C. dactylon, K. yomena, and S. americanum completely inhibited anthracnose infection in cucumber.