Key Technology And Synergistic Effects Of Chenmical Control On Sagittaria Trifolia L. In Rice

Sagittaria trifolia L.is malignant weeds in paddy fields in Northeast China.It has a serious resistance to many herbicides in paddy fields.Effective herbicides become less and less,the inhibitory effect on rice yield is very obvious.So it is urgent to find effective ways to control S.trifolia.This experiment is carried out by two aspects of chemical composition and functional auxiliaries.The toxicity of four herbicides on S.trifolia was determined.The combination of the bentazone and fluroxypyr and the combination of MCPA-Na,fluroxypyr and penoxsulam selected the best proportion.Then the synergistic effect of inorganic salts,oil additives and organosilicon additives on the four herbicides was tested.The formula combination with synergistic effect was screened through the ratio change of auxiliary agent.Then use the selected formula to discuss the problem of dosage.In the end,the feasibility of the two combination methods was proved by the field effect experiment and the safety of rice was determined.Four kinds of chemicals on the determination of virulence of S.trifolia.The stemleaf spray method recommended by FAO determination of MACP-Na,bentazone,fluroxypyr and penoxsulam in S.trifolia,The ED50 are 510.5 g a.i./hm²,1252.9 g a.i./hm²,157.6 g a.i./hm² and 119.0 g a.i./hm² respectively.Therefore,the determination of four herbicides on the activity sequence of S.trifolia is: penoxsulam> fluroxypyr> MACP-Na> bentazone.The combination of Bentazone and fluroxypyr and the combinationof MACP-Na,fluroxypyr and penoxsulam were studied thejoint effect,determined the best ratio and safety on rice.The co-toxicity coefficient?CTC?was applied to evaluate the combined effect of the two kinds of pesticides on S.trifolia.The results showed that the combination of bentazone and fluroxypyr had synergistic effect on 4.2:1?The CTC is 161.49?,Analysis of the safety of this combination to rice based on DPS Duncan`s new polarization difference method,the difference of rice plant height and fresh weight was not significant.When the combination of MACP-Na,fluroxypyr and penoxsulam as 8:9:5 has obvious synergistic?The value is 155.27?.The selectivity index of six ratios ofthe combination of MACP-Na,fluroxypyr and penoxsulam to rice is 7:7:6<7:8:6<3:4:3<6:9:7<7:9:7<8:9:5.When the ratio is 8:9:5,the safety of rice is the highest?the selectivity index is 2.707?,And 7:7:6 is the least safe for rice?the selectivity index is 1.522?.The Synergistic effect of functional additives and herbicides mixed on S.trifolia.Preliminary screening of auxiliaries,The synergistic effect of ammonium sulphate and oil additives on herbicides is the most obvious.The fresh weigh control effects reached 83.9% and 77.3%.The efficiency of control was increased by 39.3% and 32.7%,relative to the control was treated with MCPA-Na?450 g.ai/hm²?and the fresh weigh effects reached 78.5% and 65.6%.The efficiency of control was increased by 46.6% and 23.7%,relative to the control was treated with bentazone?750 g.ai/hm²?.Therefore,the optimum ratio of the mixture of ammonium sulphate and oil additives is determined.In the test of the ratio change of MACP-Na and auxiliary agent,It is found that the dosage of oil additives is 1.5L/hm² and 40,80 and 160 mmol/L.High effect control of S.trifolia,The fresh weight control effect were 80.3%,82.9% and 86.8%,efficiency rate reached more than 37.4%.When bentazone and the group of agents are used in combination,the fresh weight control effect were 74.9%,and 76.8%,increasing by more than 43.0%.Study on the use of oil additives?1.5L/hm²?and ammonium sulfate?80mmol/L?for pesticide.In the pesticide reduction test,the ED₅₀ and ED₉₀ of MCPA-Nawere 2.73 times and 3.68 times higher than that without adding additives.And the ED₅₀ and ED₉₀ of bentazonewere 4.24 times and 1.89 times.It can be concluded that the combination of prevention and treatment has the synergistic effect of S.trifolia.when mixed with MACP-Na and bentazone,the selectivity for the rice was higher and no harm occurred.Field efficacy experiments of the combination of MACP-Na,fluroxypyr and penoxsulam and auxiliary combination were determined on weeds in paddy field.When the pesticide combination was mixed according to 8:9:5 and the dosage were 500,800,1000 and 1750 g a.i./hm²,the total plant control effect were 58.5%,69.4%,78.5% and 81.4% and the total fresh weight of 30 days after the herbicides were 62.4%,72.9%,82.1% and 83.3%.The total plant control efficiency reached 18.8%,42.0%,63.4% and 71.4% and the total fresh weight control efficiency reached 39.0%,49.3%,74.6% and 78.9% after the combination of MCPA-Na.The total plant and fresh weight control efficiency reached 14.3%,32.1%,52.7% and60.7% and 24.4%,42.5%,55.2% and 62.4% respectively after the combination of bentazone.There was no significant difference between the treatment area and the control area for 30 days after the treatment of rice.Therefore,it s proved that these two ways are highly safe to apply to rice fields.It has a good inhibitory effect on weeds and the two methods can be used in paddy field.