Acetone leaf extracts of seven invasive weeds have promising activity against eight important plant fungal pathogens.
Extracts of many plant species have substantial antifungal activity, therefore the use of plant extracts with good activity against plant fungal pathogens could lead to the development of inexpensive and environmentally acceptable fungicides based on locally available natural products. Because large quantities of invasive weeds are available we decided to determine the antifungal activity of acetone extracts of seven invasive weeds (Aristolochia elegans, Chromolaena odorata, Ipomoea alba, Passiflora suberosa, Passiflora subpeltata, Solanum seaforthianum and Tecoma stans). The activity was determined against eight plant fungal pathogens viz Rhizoctonia solani, Fusarium oxysporium, Penicillium janthinellum, Penicillium expansum, Aspergillus parasiticus, Aspergillus niger, Pythium ultimum and Phytophthora nicotiana. Extracts of some invasive plant species had better activity against some fungal pathogens than some commercial fungicides. P. suberosa had promising antifungal activity with an average minimum inhibitory concentration (MIC) of 0.09 mg/ml. Tecoma stans extracts were not as active (average MIC 0.55 mg/ml). This extract, however contained compounds that yielded clear inhibition zones in bioautography making it easy to isolate the active compound by bioassay guided fractionation.