Efficiency of Allelopathy from Hairy Beggarticks (Bidens pilosa L.) in Weed Control

Abstract

Hairy beggarticks (Bidens pilosa L.) is an invasive weed wildly distributed in tropical and sub-tropical regions of the world. It causes losses in crop more than 40 countries and exhibits allelopathic effects on numerous crops. The objectives of this study were to determine application methods of allelopathy from B. pilosa on weed control and to estimate mechanisms of action of allelopathic chemicals. Allelopathic materials were prepared by collected fully expanded leaves of B. pilosa and oven dried at 45 °C for 72 hr, then were ground finely in an electric grinder. Soil and B. pilosa powder were mixed with the varying ratios of 10:0, 8:2, 6:4, 4:6 and 2:8 (w/w). Whilst seeds of Cyperus iria, Echinochloa colona and Phaseolus lathyrodes were germinated in these soil ratio for 7 days. The results showed that seed germination of three weeds species was over 50% decreasing at the ratio of 8:2 and completely decreased at the ratio of 6:4. Then, the aqueous extract of B. pilosa were produced to test on three weeds species. The extracts were applied at the concentrations of 0, 12.5, 25, 50, and 100 mg/ml by seed soaking for 7 days. The results represented that seed germination of C. iria, E. colona and P. lathyrodes was signicantly decreased at the concentration of 25, 50, and 100 mg/ml, respectively. The same concentrations of extracts were used as foliar application to 7 d-old seedlings of tested weeds to investigate phytotoxic symptoms. Three days after foliar application, there were no severe injury in weed seedlings indicating low efficacy of the extracts on leaf cell penetration. Therefore, the allelopathy of B. pilosa could suppress seed germination by using powder and extract application, nevertheless it could not suppress seedling growth by using foliar application.