| Ammannia coccinea Rottb.is a newly discovered alien invasive plant in mainland China.In order to provide useful information for the risk assessment and integrated management of A.coccinea,the sensitivity of A.coccinea to some commonly used herbicides and its competition with rice were investigated.Furthermore,preliminary assays was implemented to screen suitable herbicides for the chemical control ofA.coccinea and other weeds.The results indicatted that four biotypes of A.coccinea(JX092,JX093,JX094,SH037)were sensitive to bensulfuron-methyl(BSM),and their corresponding ED50 values were 0.20,0.20,0.22 and 0.25 g ai/ha,respectively.Besides,seven biotypes of A.coccinea(SX148,HZ050,JX096,JX099,JX100,JX101 and SX040)were found to be resistant to BSM,with the resistance index(RI)of 56.62,56.00,19.90,26.19,17.48,14.62 and 26.86,respectively.The ED50 of penoxsulam,bispyribac-sodium,pyribenzoxim to biotype SH037 were 0.29,0.27,2.49 g ai/ha respectively,while the biotype SX040 were found to be resistant to the above mentioned herbicides,with the corresponding RI values of 12.29,17.32 and 4.29.Besides,the ED50 of clomazone,prometryn,pendimethalin,oxadiazon,oxadiargyl to SH037 were 33.06,67.62,132.42,38.64,3.16g ai/ha,respectively,and all the RI of SX040 to these herbicides were less than 1.3.It was observed that the A.coccinea had evolved middle or high resistance to BSM,and cross resistance to penoxsulam,bispyribac-sodium and pyribenzoxim,which was the first report of resistance of A,coccinea.to ALS inhibitors in China.The results of competition tests indicated that the height of A.coccinea was decreased by 21.7%and 38.8%in densities of 32 and 64 plants/m2,when compared to treatment of the 4 plants/m2(79.33 cm);Compared to the treatment of 4 plants/m2,the branches of A.coccinea in densities of 16,32,64 plants/m2 were decreased by 11.6%,21.6%,38.8%,respectively;the biomass of A.coccinea were decreased by 20.5%,46.8%,79.5%,respectively;the seed weight of A.coccinea were reduced by 18.3%,45.0%,and 81.4%,respectively.Compared to control treatment,the height of rice in densities of 32,64 plants/m2 were decreased by 10.0%and 15.0%,respectively;the tiller numbers of rice in the weed densities of 8,16,32,64 plants/m2 were reduced by 10%,14.3%,26.7%and 43%,and the panicles number were also reduced by 15.8%,29.8%,35.6%,44.1%;the rice yields in the densities of 4,8,16,32,64 plants/m2 were decreased by 22.77%,31.69%,53.70%,72.28%and 79.68%.So,with the increasing of weed density,the height,branch number,biomass,seed of A.coccinea were generally reduced.Besides,it also led to the significant reduction of height,tiller number,panicle number,and seed setting of rice.Given the density of 4 plants/m2,A.coccinea could lead to 22.77%yield decrease of rice.Thus,the alien invasive A.coccinea indeed have great harm to the rice system.The rice injures were observed in the recommended dose treatment of butachlor,clomazone,prometryn,and ZJU3 which were pre-emergence treated 7 days before sowing.Both the inhibition rates of pretilachlor(526 g ai/ha),ZJU1(557 g ai/ha),ZJU2(360 g ai/ha),and ZJU3(225 g ai/ha)g ai/ha to plant height and tillering of rice were below than 8%,and the reduction of total fresh weight were above 94.93%.It means that ZJU1,ZJU2,and ZJU3 are relatively to rice and has the potential to be developed as pre-emergence herbicides. |
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