Study On The Biology, Ecology And Chemical Control Of Japanese Lovegrass (Eragrostis Japonica)

The purpose of this study was to investigate biology, ecology and chemical control of Eragrostis japonica ( Thunb.) Trin. (Japanese lovegrass). Eragrostis japonica is a new important grass weed in paddy rice field of Huaian, a city in Jiangsu Province. The results indicate the reason why Eragrostis japonica can develop in the both in paddy and upland and why Eragrostis japonica has the potential to become a weed of major significance in the future. These laboratory studies can then be correlated with field observations and management strategies. The biology of Eragrostis japonica include germination, plant characteristics and fructifying. The germination and seedling emergence is to imply the effect of temperature, light, pH, osmotic potential, salinity, soil moisture content and burial depth on seed germination and seedling emergence of Eragrostis japonica. The ecology include the occurrence in the field and the influence of different density and associated periods on the growth of Eragrostis japonica. The chemical control is to select the suitable herbicides to control the develop of Eragrostis japonica. Results were listed as followed:1. Biological characteristicsIt is found that the seeds of Eragrostis japonica have not dormancy. Eragrostis japonica can germinate under constant temperature between 20～40 ℃, but the most appropriate temperature for germination (above 90%) is between 25～40℃. Seeds were able to germinate over a wide range of temperature regimes but the optimal temperature regime for germination (above 95%) was found to be between 30℃/20℃ (day/night) and 40℃/25℃ (day/night). Seeds could not germinate in the dark, suggesting that seeds of this species are light sensitive. Seed germination showed little change across a range of pH values. Seed germination was observed when seeds were placed in a salt solution of 0.16 M. Seed germination was sensitive to osmotic stress. Germination rate was the highest when the soil moisture content was above 40%. Seeds had the greatest seedling emergence when seeds were sown on the surface of the soil, with no seedling emergence when the seeds were buried in the soil at the depth of 0.4 cm. The average plant height of Eragrostis japonica is 115.15cm, fresh weight of it is 2.15g, stems of plant is 3.18, productive tillering nodes are 3.52, the inflorescence length is 38.18cm, inflorescence weight is 0.55g and the grain number per fruit is 5535.7.2. Ecological characteristicsEcology exploration showed that the occurrence of Eragrostis japonica in the field reached 11 per 0.25m2, the average is5.6 per 0.25m2.The investigation of plant height and fresh weight shows that the rapid increasing period of Eragrostis japonica occurred at 20days after sowing. The height of plant is 6.36cm, the fresh weight of the plant is 0.018g. The competition of Eragrostis japonica and rice also be investigated. The plant weight, fresh weight and yield are influenced significantly by the density and associated period. As the early growth of Eragrostis japonica is slowly, the influence of it when the associated period is 30 days is slightly. 3. Chemical controlIn order to screen the herbicides to control Eragrostis japonica in paddy field,5 soil-applied herbicides and 11 foliar-applied herbicides are used by pot-spraying method. The data show that 5 soil-applied herbicides and 2 foliar-applied herbicides could control Eragrostis japonica in the range of recommended dose 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, the optimum formulation was obtained as follows:metamifop to pyribenzoxim (ration of 4:1).