The Resistance Of Cyperus Difformis To AHAS Inhibitor And Management

Cyperus difformis L. is an annual weed belonging to the sedge family. It is one of the worst weeds worldwide and has infested the paddy field in south and north regions China. The efficacy of the AHAS inhibitor herbicides such as pyrazosulfuron-ethyl and bensulfuron is obviously decreased because the herbicides have been used for many years.The experiments were conducted to evaluate the resistance and cross-resistance of Cyperus difformis to AHAS inhibitor pyrazosulfuron-ethyl. Whole plant bioassay was used in the experiments to test the resistance level of Cyperus difformis collected from paddy fields in Hubei, Liaoning, Jiangsu and Hunan province. In addition, bentazone, MCPA, pendimethalin, halosulfuron methyl, the mixture of MCPA and bentazon, the mixture of penoxsulam and cyhalofop-butyl were applied to study the control efficacy of different herbicides on the resistance population of Cyperus difformis. The objective of this paper is to evaluate the resistance level and control efficacy of different herbicides to Cyperus difformis resistance populations. In addition, provide a theoretical basis for practical detecting resistant weeds and guiding the scientific and rational usage of herbicides.The results were as follows:1. Under4times of the recommended doses of pyrazosulfuron-ethyl different populations of Cyperus difformis had different control efficacy. The populations of H1, H4and H3, H7, H10, treated by pyrazosulfuron-ethyl, which were collected from Changde and Yiyang of Hunan province, showing that the survival rate could attain100%. The survival rate of H5and H9populations attained10%and30%respectively, which also collected from Changde and Yiyang. Other Cyperus difformis populations' mortality could reach up100%when treated with the same doses of pyrazosulfuron-ethyl.2. The populations of H1, H3, H4which were collected from Changde, had different resistance level to pyrazosulfuron-ethyl, and the ED50of which could attain6397.17g a.i./hm2,194.18g a.i./hm2,198.06g a.i./hm2, respectively. The resistance index of H1population attained3998.32when compared with the sensitive population H2, whose ED50was merely1.60g a.i./hm2. 3. The population of H1, H3and H4showed cross-resistance to penoxsulam, bispyribac sodium salt and bensulfuron methyl. The ED50of population H1to different herbicides, which described as above, were21.85g a.i./hm2,109.86g a.i./hm2,232.43g a.i./hm2, respectively. The ED50of population H3to above three different herbicides were3.25g a.i./hm2,16.85g a.i./hm2,4.74g a.i./hm2, respectively. The ED50of population H4to three different herbicides were13.63g a.i./hm2,47.39g a.i./hm2,28.59g a.i./hm2, respectively.4. The results showed that bentazone, MCPA, pendimethalin, the mixture of MCPA and bentazon, the mixture of penoxsulam and cyhalofop-butyl had high control efficacy (?90%), which could reach up100%, to the population of H1, H3and H4. Halosulfuron methyl had high control efficacy only to H2and H3, but low control efficacy to H1and H4. Under recommended doses the fresh weight efficacy of population H1and H4were merely19.47%,22.72%, respectively.In this paper we evaluated the resistance level of Cyperus difformis to pyrazosulfuron-ethyl and the cross-resistance level to penoxsulam, bispyribac sodium salt, bensulfuron methyl. Besides,6paddy herbicides were applied to study the control efficacy to the resistance population of Cyperus difformis. The results of this paper would lay a foundation for Cyperus difformis resistance management and research.