Study On The Biology, Ecology And Chemical Control Of Yerbadetajo(Eclipta Prostrata)

This study is focused on the biology, ecology and chemical control of yerbadetajo (Eclipta prostrata), which thrives in upland field and paddy field in the Yangtze River Basin. This study may also explains why the yerbadetajo has evoled to be a malignant weed. The biology of yerbadetajo, including plant characteristics, fructifying traits, germination, occurrence in Jiangsu Province, was studied. In this paper, the population dynamics, spatial distribution pattern and the competition with soybean, were explored. The susceptibility of yerbadetajo populations to bensulfuron-methyl and nicosulfuron was evaluated. Available techniques used for chemical control of yerbadetajo were studied in laboratory. Results obtained were listed as following:1. Biological CharacteristicsIt was found that the seeds of yerbadetajo could germinate at a range of temperatures from25to40℃. Seed germination was strongly stimulated by light, suggesting that seeds of this species are photoblastic positively. Seeds could germinate at pH ranged from4to10(93%to100%). Also seeds could tolerate wide ranges of salt stress, and germination occurred even at0.15mol/L(42.22%), while it was highly sensitive to water stress, under which the percentage germination would be decreased from97.78%to4.44%with the descending of water stress from0to-0.5MPa. Seeds sown on the soil surface gave the greatest percentage seedling emergence (92.50%) in plastic trays, and no seedlings emerged when seeds were buried in soil at depths of0.5cm. Fruiting traits of yerbadetajo were investigated in2010in different habitats. Its average plant height was63.17cm, fresh weight was47.21g per plant, productive tillering nodes were8.52, productive fruits were101, grain number per fruit was89.20, and1000-grain weight was0.4697g. The seeds emergenced in June to July, then exploded and fructified from June to October.2. Ecological CharacteristicsEcology exploration of yerbadetajo showed that the emergence fastigium was observed12to18days after sowing of soybean. The competitive ability of Yerbadetajo with soybean has been investigated. Data showed that the rapid increasing period of plant height and fresh weight of yerbadetajo occurred at40days after sowing of soybean, which was later than soybean by20days. Moreover, the number of productive plant, pod number per plant and yield of soybean were declined significantly with increasing density of yerbadetajo but not for plant height. In soybean, yerbadetajo was dispersed as aggregated distribution, because of affeetions of environment, including tillage, crop planting, fertilizer application, weed control and other natural elements. The weed populations were in the following order:Dry-Seeded rice> Water-seeded rice> Transplanted rice. In addition, the weed seedlings in upland field were complicated.3.Chemical ControlThe susceptibility of10yerbadetajo populations to bensulfuron-methyl or nicosulfuron indicated that resistance to bensulfuron-methyl or nicosulfuron had not occurred. In addition, bensulfuron-methyl and nicosulfuron could control yerbadetajo effectively at labeled dose. In order to screen out effective herbicides that could be used to control yerbadetajo in upland field and paddy field, the suspectibility of yerbadetajo to12soil-applied herbicides and10foliar-applied herbicides were evaluated by pot-spraying method. The investigation revealed that more than half of the herbicides could control yerbadetajo effectively. Based on the principles of expanding weed controlling spectrum, reducing the cost and increasing effect, the screening of the optimum formulation was conducted by Gowing’s method and isoble method, the three optimum formulation were obtained as follows:butachlor to oxadiargyl(ration of6:1), mesotrione to nicosulfuron (ration of2.5:1), pendimethalin to bensulfuron-methyl (ration of8:1). Three groups of the mixtures were applied in greenhouse, and all mixtures got the general effects over85%against the whole weeds.