Ning Ll，Hui YlN，Haibin CHANGHuanggang Academy of Agricultural Sciences，Huanggang 438000，China

The Effect of Three New Fungicides against Rice Sheath Blight in Field Experiment

Ning Ll*，Hui YlN，Haibin CHANG
Huanggang Academy of Agricultural Sciences，Huanggang 438000，China

［Objective］The aim was to study the effect of three new fungicides against rice sheath blight in field experiment.［Methods］The experiment set up 7 treatments with three times of repetition and designed by random grouping.By using 5 sampling points in each plot，and investigating continuous 4 holes of each point，total plants，diseased plants and disease degrees were recorded.Then disease index and control efficiency were calculated，and variance analysis was carried out. ［Results］300 or 450 ml/hm2azoxystrobin+difenoconazole 325 g/L SC had better control efficiency to rice sheath blight and had no phytotoxicity effect，we should use it at the initial disease stage and continuously spray 2-3 times.［Conclusion］The experiment provided theoretical basis for controlling rice sheath blight using fungicides.

Rice sheath blight；Fungicides

R ice sheath blight（also called rice scald），caused by Rhizoctonia solani，is one of the most destructive rice diseases currently.It often occurs in the condition of high temperature and high humidity，if terrible，the rice may without heading or cause blighted grains，thereby rice grain weight will decrease，causing substantial yield loss.Huanggang is located in East Hubei，South Dabie Mountain，the north bank of the middle reaches of the Yangtze River，as well as the middle part of the Jingjiu Railway.Rice is the traditional predominant industry and has the largest growing area in Huanggang.Huanggang has already developed as the important quality grain and oil base nationwide.Nie Yafeng et al.［1］and Ren Xiaoping et al.［2］both have received comparatively good effects in preventing rice sheath blight respectively using marine microorganism sand antagonistic bacteria separated from rice seed and rice plant.Recently，the prevention of rice sheath blight using antagonistic microorganisms has shown a good prospects，a lot of funguses，bacteria and actinomycetes［2-3］having antagonistic effect to rice sheath blight have been found. Meng Dechao et al.［4］obtained 4 bacterial strains having strong antagonistic effect on Rhizoctonia solani；Song Wenwen et al.［5］reported 2 bacterial strains having stronger antagonistic activity to Magnaporthe oryzae.At present，Huanggang has promoted ratooning rice planting patterns vigorously；rice sheath blight not only does severe harm to rice production of the present season，but also is the most devastating disease of ratooning rice. Therefore，in this study，the experiments of several bactericides were carried out to provide ideal methods for rice sheath blight prevention.

Materials and Methods

Test medicaments

In this experiment，we chose trifloxystrobin·tebuconazole 75%WDG and azoxystrobin+difenoconazole 325 g/L SC from Shanghai Taihe Chemical Co.，Ltd.，as well as nativo from Bayer Crop Science China Co.，Ltd.

Experimental field

Medicament experiments were carried out at the experimental base ofHuanggang Academy of Agricultural Sciences.The experimental field was flat，soil fertility was uniform，the preceding crop was rice，and rice sheath blight occurred frequently for years in the field.

Experimental design

The experiment set up such 7 treatments as 150，225，300 g/hm2trifloxystrobin·tebuconazole 75%WDG，300，450 ml/hm2azoxystrobin+difenoconazole 325 g/L SC，225 g/hm2nativo，and CK（clean water）.The experiment plot area was 30 m2，and the experiment was repeated three times and designed by random grouping.

Experimental methods

On September 3 of 2014 （full incidence beginning period）and September 20 （the peak period），fungicides were sprayed once for each with manual sprayer［4-5］，and water volume was 675 kg/hm2.After that，sprayer must be cleaned to avoid cross-contamination.

Investigation Contents and Methods

Safety observation After spraying fungicides，we should aperiodically observe the effect of fungicides on the safety of rice.

Investigation methods7 d after spraying fungicides，the occurrence of rice sheath blight was investigated.According to the grading criteria of symptoms of rice sheath and blade，taking plant as the unit，using 5 sampling points in each plot，and investigating continuous 4 holes of each point，total plants，diseased plants and disease degrees were recorded.Then disease index and control efficiency were calculated，and variance analysis was carried out［6］.

The grading criteria of rice sheath blight were as follows:0 grade:no disease；1 grade:the 4thleaf and all sheaths and leaves below were diseased；3 grade:the 3rdleaf and all sheaths and leaves below were diseased；5 grade:the 2ndleaf and all sheaths and leaves below were diseased；7 grade:flag leaf and all sheaths and leaves below were diseased；9 grade:the whole plant was attacked，died in advance［7］.Every 7 d after spraying fungicides，the fungicide effect was surveyed，the computational formulas were as follows:

Disease index=［Σ （Diseased plants each grade×Value of corresponding grade）/Total plants×9］×100

Control efficiency（%）=［（Disease index of CK group-Disease index of treatment group）/Disease index of CK group］×100

Results and Analyses

Safety analysis

After spraying fungicides，we investigated that rice of each treatment group grew normally，there was no phytotoxicity，which indicated that each test medicament had positive effect on rice growth.

Control efficiency analysis

Through investigating field diseases twice and comparing the data， the results （Table 1）indicated that azoxystrobin+difenoconazole 325 g/L SC had better control efficiency on rice sheath blight，moreover，each treatment group was better than CK group，in which 7 d after the first fungicide application，the control efficiency of azoxystrobin+difenoconazole 325 g/L SC （450 ml/hm2）and trifloxystrobin· tebuconazole 75%WDG （225 g/hm2）on rice sheath blight was the best，and the control efficiency reached 53.97% and 48.47%，respectively，which had extremely significant difference comparing with CK group；other fungicide treatments had not significant control efficiency.After the second fungicide application，the control efficiency of each fungicide was improved obviously，forming a very significant difference with CK group，for example，the control efficiency of azoxystrobin+difenoconazole 325 g/L SC （450 ml/hm2）reached 89.79%；there was no difference of each fungicide treatment.

Conclusions

The control efficiency of different fungicides on rice sheath blight showed that azoxystrobin+difenoconazole 325 g/L SC had better control efficiency on rice sheath blight，and had no phytotoxicity effect to rice growth.Thus，it can be popularized in the prevention of rice sheath blight in future.Moreover，we suggested that we’d better use 300 or 450 ml/hm2of azoxystrobin+difenoconazole 325 g/L SC at the initial disease stage and

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三種新型殺菌劑防治水稻紋枯病田間藥效試驗

李 寧*，殷徽，常海濱 （黃岡市農(nóng)業(yè)科學(xué)院，湖北黃岡 438000）

［目的］探討3種新型殺菌劑對水稻紋枯病田間藥效作用。［方法］試驗共設(shè)7個處理，重復(fù)3次，隨機(jī)區(qū)組排列，每小區(qū)采取5點(diǎn)取樣法，每點(diǎn)調(diào)查相連4穴，共計20穴。記載總株數(shù)、病株數(shù)和病級數(shù)。計算病指和病指防效，并進(jìn)行方差分析。［結(jié)果］嘧菌酯+苯醚甲環(huán)唑 325 g/L SC 300 ml/hm2或 450 ml/hm2對水稻紋枯病有較好的防治效果，無藥害作用，在水稻紋枯病發(fā)病初期使用，連續(xù)噴藥2-3次。［結(jié)論］為采用殺菌劑防治水稻紋枯病提供理論依據(jù)。

水稻紋枯??；殺菌劑

00000000。E-mail：lining040305027@163.com。

2014-12-19

2015-02-07

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December 19，2014Accepted:February 7，2015