Efficacy Assessment of 50 g/L Pinoxaden EC for the Control of Phalaris arundinacea in Barley Field

Wenxiang XIAO,Jizhi MENG,Zuobin YANG,Mengdao LIU,Tingchu MA,Diyun LIANG,Rongquan YANG,Lijuan ZHANG,Xiwu GAO

1.Plant Protection and Inspection Station,Baoshan Yunnan 678000,China;

2.Agricultural Scientific Research Institute,Baoshan Yunnan 678000,China;

3.Protection and Inspect Station of longyang district,Baoshan Yunnan 678000,China;

4.Plant Protection and Inspection Station,Kunming 650000,China;

5.The National Agro-Tech Extension and Service Center,Beijing 100000,China;

6.China Agriculture University,Beijing 100000,China

Responsible editor:Yingzhi GUANG Responsible proofreader:Xiaoyan WU

Phalaris arundinacea (Phalaris arundinacea L.),also known as reed canary grass and Yuancaolu,belongs to Phalaris sp.(Poaceae) including 22 species[1],in which P.arundinacea is most widely distributed,mainly in temperate areas such as North America,Northern Europe and Asia,and can be found in Northeast China,North China,Northwest China,East China,and Central China[2].P.arundinacea grows in wet areas and is not rigid for environment.Two species are widely distributed in Baoshan city of Yunnan province[3],which are Phalaris minor Retz.and Phalaris paradoxa L.,respectively.All of Phalaris minor Retz.,Phalaris paradoxa L.,and wheat and barley are Poaceae plants with similar appearances,and it is thus difficult to identify them in field,and to prevent and control chemically and manually[3].P.arundinacea has good stress resistance and high yield and nutritional value,and is widely used in forage grass,constructed wetland,biological energy source and papermaking raw material[4-6].

Yunnan is located at border area of Southwest China,bordering on Vietnam and Laos.Yunnan is abundant in biodiversity,with rampant exotic invaders[7-8].Barley is an important food crop in Yunnan,however,it has been infected by exotic invasive weeds including P.arundinacea in recent years,and its yield and quality have been seriously impacted.In China,P.arundinacea was distributed in Yunnan as early as 10 years ago[9].There already have been researches for mastering biological and ecological characteristics and accumulating practical experience in controlling exotic invasive pests[10-13].Pinoxaden is a phenyl pyrazoline type herbicide developed by Syngenta,mainly used for cereal fields,which can effectively prevent and kill off a variety of important annual gramineous weeds,such as Avena,Lolium,Phalaris and Setaria,with high safety for barley and wheat,and thus can be applied in a long time period from seeding stage to advanced stage[14].Pinoxaden is the most effective herbicide for controlling P.arundinacea in barley fields[15]in a dose range of 900-1 200 ml/hm2,and has a control efficacy above 97%,without phytotoxicity to barley and broad bean[16].Pinoxaden belongs to phenyl pyrazoline type herbicides,the action mechanism of which is that acetyl-CoA carboxylase (ACC) inhibitor inhibits the synthesis of fatty acid,thus stops cell growth and division and damages lipid-containing structures in cytomembranes,resulting death of weeds[14].Fenoxaprop-P-ethyl is a kind of herbicide falling into aryloxyphenoxypropionates (AOPPs),while AOPP herbicides have the disadvantages of single action target with a dose increasing with years,and the decreasing efficacy is prone to induce production of resistant weeds[17].It has been reported abroad that Phalaris arundinacea and Alopecurus myosuroides produced resistance to AOPP herbicides[18-19].

In the early 1980s,with seed allocation and transportation,P.arundinacea appeared at north area of the dam of Baoshan City in Yunnan Province,and it occurred in large area of Baoshan City until the 1990s.P.arundinacea is on the increase in Baoshan city recently,especially serious in Longyang district of Baoshan city.Barley was cultivated in an area of 29 thousand hm2in Baoshan City in 2014,and the occurrence area of P.arundinacea was of 10-13 thousand hm2,resulting in a loss of about 10%.In Longyang district,barley had a cultivated area of 6 thousand hm2,with an occurrence area of 3 thousand hm2,resulting in a loss above 30%,up to 70%in some field.The cultivated area of wheat was of 13 thousand hm2in Baoshan city,with an area of 2.7-3.3 thousand hm2harmed by P.arundinacea;and wheat was cultivated in an area of 4.7 thousand hm2in Longyang district,with a P.arundinacea occurrence area of 1.3 thousand hm2and seriously harmed area of 0.8 hm2.Recently,P.arundinacea mainly occurs in barley field,wheat field,broad bean field,oilseed rape field and winter fallow field.The harm is especially serious in barley and wheat fields,and peasants mainly adopt manual weeding to control it yet though the effect is not ideal,or the weed is controlled with fenoxaprop-P-ethyl EW,which is very prone to phytotoxicity in barley fields at a low temperature in use for weeding.Aiming at the prominent problem in production,efficacy assessment of 50 g/L Pinoxaden EC (Aixiu)for the control of P.arundinacea in barley field is conducted,in order to provide scientific basis for the control of P.arundinacea in barley field.

Materials and Methods

Basic information of test field

The test field was located at Dongguan Village,Hetu Town,Longyang District,Baoshan City,Yunnan province,with an altitude of 1 648 m,and an annual average temperature of 15.6 ℃.The frost-free season at the area is 204 days.In the test area,the annual rainfall is 970-1 290 mm,in which the rainfall from June to October accounts for 80%.The soil is clay with a fertility better than average at pH of 6.5.The test area is suitable for planting a variety of plants,mainly producing rice,barley,wheat,beans,vegetables and so on.During the test period,fine weather was dominant,while light to moderate rain fell 10 days after herbicide application for 2 days with a rainfall of 0.2 mm; the average temperature was 10.5-15 ℃,with a highest temperature of 16-25 ℃and a lowest temperature of 1-6 ℃in 10 days; and the relative humidity was 54%-68%.

Test herbicides

Fifty g/L pinoxaden EC(Aixiu)was purchased from Swiss Syngenta crop protection Co.,Ltd; and 69 g/L fenoxaprop-p-ethyl EW (Dabiaoma)was purchased from Bayer Crop Science(China)Co.,Ltd.

Test design and herbicide application method

The test was designed as follows:50 g/L pinoxaden EC (Aixiu) A,900 ml/hm2;B,1 200 ml/hm2;C,1 500 ml/hm2;D,2 400 ml/hm2;E,69 g/L fenoxapropp-ethyl EW(Dabiaoma),1 050 ml/hm2;F,manual weeding;and G,clear water as control.The test had 7 treatments and used randomized block design,with four repetitions,and the plot areas were of 20 m2.

The test was carried out on February 8 in 2014,at 4-5 leaf stage of barley and 3 -4 leaf stage of P.arundinacea,herbicide was sprayed onto stem leaves of P.arundinacea once according to experiment treatments using 3WBS-16 (A) backpack type manual sprayer having a pore diameter of 1.6 mm,and the spray quantity was of 900 kg/hm2.The treatment F was subjected to manual weeding.

Investigation,record and measurement method

The reaction of P.arundinacea to herbicides and the phytotoxicity to barley were observed 7,15,30 and 45 days after herbicide application.The number of P.arundinacea individuals was investigated at the 15th,30thand 45thday,and the control efficacy was calculated.Each plot was sampled at three points,each of which had an area of 0.25 m.The number of remaining plants in each sampling point was recorded,and the fresh weight of overground parts of remaining plants was weighed,to calculate the efficacy according to formula(1).

In which:PT was the number of remaining weeds (fresh weight) in a treatment plot; CK was the number of remaining weeds(fresh weight)in corresponding control.

Results and Analysis

Control efficacy

Seven days after herbicide application,with 50 g/L pinoxaden EC,treatment Ashowed a light toxic symptom;in treatment B(1 200 ml/hm2)and treatment C(1 500 ml/hm2),P.arundinacea showed an obvious toxic symptom;in treatment D(2 400 ml/hm2),P.arundinacea showed a more serious toxic symptom,with leaves turning yellow; and with the control herbicide fenoxaprop-p-ethyl EW(Dabiaoma),in treatment E(1 050 ml/hm2),P.arundinacea showed a light toxic symptom.

Fifteen days after herbicide application,P.arundinacea in treatment A presented an obvious toxic symptom,with a control efficacy of 24.67% ;treatment B showed that P.arundinacea started to turn yellow,with a control efficacy of 41.98%;the P.arundinacea in treatment C started to turn yellow,with a control efficacy of 51.87% ; the yellowing of P.arundinacea in treatment D was aggravated,and some were withered and died,achieving a control efficacy of 51.87%;in treatment E,P.arundinacea showed obvious toxic symptom and started to turn yellow,and barley showed an obvious phytotoxicity symptom,achieving a control efficacy of 21.31%;and in treatment F,P.arundinacea started to grow again,and the efficacy was of 71.74%(Table1).

Thirty days after herbicide application,P.arundinacea in treatment Astarted to turn yellow and wither,and the efficacy calculated according to remaining plant number was of 73.68%;treatment B showed withered and died P.arundinacea in a large area,with a control efficacy of 81.52%;treatment C also showed a large area of withered and died P.arundinacea,with a control efficacy of 90.84%;most P.arundinacea was died in treatment D,achieving a control efficacy of 95.89%; P.arundinacea in the control E started to wither,most leaves of barley showed obvious phytotoxicity symptom,and the efficacy was of 58.22%; and P.arundinacea in treatment F continued to grow,and the efficacy was of 54.77%(Table1).

Forty five days after herbicide application,P.arundinacea was withered and died in large area,and treatment A and treatment B achieved control efficacies of 98.08% and 98.94%,respectively; P.arundinacea in treatments C and D was all died,with a control efficacy of 100%; phytotoxicity symptom in barley was disappeared in treatment E,the growth regained,and the control efficacy was of 74.07%;and the treatment F subjected to manual weeding had a control efficacy of 49.97%(Table1).

According to fresh weight of remaining P.arundinacea,efficacies were assessed,in which the efficacy of treatment A was of 97.04%; that of treatment B was of 98.76%; that of treatment C was of 100%;that of treatment D was also of 100%;that of treatment E was of 72.93%; and that of treatment F was of 51.54%(Table1).

Variance analysis showed that 45 days after herbicide application,the differences between blocks were not significant,while those between treatments were significant.Multiple comparison showed that 45 days after herbicide application,P.arundinacea stem control efficacy and fresh weight control efficacy reached the significant level between treatment G with treatments A,B,C,D,E and F;treatment F was not significantly different with treatment E,but was significantly different with treatments A,B,C and D;and the differences among A,B,C,D and E were not significant.

Influences on crops and environment

It was observed that for 50 g/L pinoxaden EC(Aixiu),phytotoxicity did not occurred at the doses of 900,1 200,1 500 and 2 400 ml per hectare,so it had a high safety for barley; and for 69 g/L fenoxaprop-p-ethyl EW (Dabiaoma),obvious phytotoxicity symptom was observed 15 days after application at the dose of 1 050 ml per hectare when the temperature was lower than 0 ℃,with leaf apexes turned yellow and withered.The phytotoxicity symptom disappeared 45 days after application,and barley continued to grow.

In the dose range of each test treatment,no harmful effect was observed on organisms in the test environment by the tested herbicides.

Conclusions and Discussion

From above comprehensive analysis results,50 g/L pinoxaden EC(Aixiu) had a good efficacy in controlling P.arundinacea in winter barley field.In the range of 900-1 200 ml/hm2,its efficacies on P.arundinacea (3-4 leaf stage) reached 97.04% and 98.76%,which were significantly better than those of 69 g/L fenoxaprop-pethyl EW and manual weeding; and when the dose reached 1500 ml/hm2,the efficacy could reach 100%.

Even at the dose of 2 400 ml/hm2,50 g/L pinoxaden achieved a control efficacy of 100% without producing phytotoxicity on barley.Fenoxaprop-pethyl gave rise to cross resistance in controlling weeds[20].Therefore,pinoxaden was a better herbicide for controlling P.arundinacea than other her-bicides[15],and also better than other control methods.These results substantially accorded with the test results obtained at other regions and the efficacies showed in literatures,and innovation was made in the aspects no phytotoxicity at low temperature (0 ℃)and the control of P.arundinacea in winter barley field in Baoshan.

Table1 Efficacy assessment of 50 g/L pinoxaden EC for the control of Phalaris arundinacea in barley field

Fifty g/L pinoxaden EC (Aixiu)was safe to barley production without producing phytotoxicity;the application at 4-5 leaf stage of barley and 3-4 leaf stage of P.arundinacea could achieve an efficacy above 97% in the dose range of 900-1 200 ml/hm2,and there was no influence on test results under a low temperature condition(0 ℃).

No bad influence was observed on arthropod in field when 50 g/L pinoxaden EC (Aixiu) was applied to control P.arundinacea in barley field.This method and result could be applied and popularized in Yunnan and even the whole nation.

We advised control tests on P.arundinacea in the field of barley after 8-10 leaf stage to be conducted,and control tests on P.arundinacea in the fields of crops including broad bean and oilseed rape to be conducted,in order to further improve application effect.

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