Field Efficacy Trial and Optimum Control Period of Rice False Smut(Ustilaginoidea virens) in Single Cropping Middle-late Rice

[Objective]The paper was to study optimum chemical agents and control periods against rice false smut( Ustilaginoidea virens) in single cropping middle-late rice. [Method]Taking chemical agents( triadimefon,armure,Jinggangmycin) as main treatments and spraying periods( within 7 d before initial heading stage,within 7 d before initial heading stage + initial heading stage,initial heading stage) as assisted treatments,the field efficacy trial and optimum control period of U. virens in single cropping middle-late rice were studied using Huanghuazhan and Jinnongsimiao as experimental materials in 2013. [Result] Three chemical agents,triadimefon,armure,Jinggangmycin,extremely reduced diseased panicle rate and disease index of U. virens,but there was no significant difference among three chemical agents. Spraying period did not have significant impact on diseased panicle rate and disease index of U. virens,whereas spraying within7 d before initial heading stage and during initial heading stage had relatively good control effect. Yield increased significantly after application of three chemical agents,and armure led to greater increase. The reason for yield increase was that seed setting rate was significantly increased,and the number of filled grains per panicle was significantly increased. Although spraying period influenced yield,the difference was not significant. [Conclusion] Triadimefon,armure and Jinggangmycin had good control effects against U. virens in single cropping middle-late rice,of which armure had better control effects. Spraying chemical agents increased seed setting rate,and further increased the number of filled grains per panicle and yield. Spraying within 7 d before initial heading stage and during initial heading stage had relatively better control effect against U. virens.

Effects of Fenaminosulf on Yield and Benefit of Single Cropping Zizania latifolia

[Objective]The paper was to normalize the application of fenaminosulf in single cropping Zizania latifolia. [Method]Effects of spraying periods,different concentrations and spraying times of fenaminosulf on yield and output value of single cropping Z. latifolia were studied.[Result]In some regions where single cropping Z. latifolia could be harvested twice per year,fenaminosulf significantly promoted formation of swollen gall,and advanced the harvest period for about 50 d. Application of 0.5 g/L（ a.i.） fenaminosulf at 150,160 and 175 d post transplanting promoted swollen gall formation and enhanced the yield of Z. latifolia.In normal single cropping Z. latifolia growing regions,once application of fenaminosulf obviously advanced harvest period and improved yield and benefit of Z. latifolia,but with the increasing frequency of use,yield and benefit of Z. latifolia decreased significantly.[Conclusion]It is recommended that 1.0 g/L（a.i.） fenaminosulf can be applied for just once at 40-60 d post transplanting of Z. latifolia.

Occurrence Regularity of Major Damage Generations of Nilaparvata lugens(Stl) in Single Cropping Medium Rice Region in Sandu County of Guizhou Province

In order to clarify occurrence regularity of major damage generations of Nilaparvata lugens( Stl) in Sandu Shui Autonomous County( Sandu County for short),Guizhou Province,a karst single cropping medium rice region,the population dynamics of N. lugens were systematically studied using the methods of light trap and systematic field survey from 2009 to 2011. The results showed that the number of immigration generations caught by light trap and the actual population of N. lugens in fields were different among three years. The daily maximum trapping numbers of N. lugens amounted to 6 688 in 2009,which were 15. 3 and 2. 5 times of that in 2010 and 2011,respectively. The peak numbers in prediction nursery were 10 777,4 630 and 1 615 heads per hundred hills in 2009,2010 and 2011,respectively. The forth and fifth generations of N. lugens were the major damage generations in single cropping medium rice fields,and the initial immigration day was significantly related with primary-peak day. The occurrence degree of adults and nymphs of N. lugens varied with years and transplanting periods,and the peak days of N. lugens nymphs were from late July to early August in 2010 and 2011. The occurrence peaks of adults and nymphs in late transplanting paddy field were later than that in the early one. Meanwhile,the coexisted various growth periods of rice,due to time differences of transplanting,were conducive to inhabitation and reproduction of N. lugens. The population dynamics of spiders and Cyrtohinus lividipennis well synchronied with that of N. lugens,but predatory capacity of spiders and C. lividipennis was not enough to control N. lugens.

Relationship between “Two Insects and One Spider” and Their Occurrence and Damage Regularity during Different Sowing Periods in Single Cropping Hybrid Rice

[Objective]The paper was to study the relationship between rice leaf roller,rice planthopper and spider and their ecological regulation ability in the field.[Method]The population dynamics of rice leaf roller,rice planthopper and spider at three different sowing and transplanting periods of single cropping hybrid rice in the treatment area with combination of 3 drug formulations and untreated area were monitored.[Result]There were significant or extremely significant positive correlations among rice leaf roller,rice planthopper and spider in single cropping hybrid rice.However,with the delay of planting and transplanting period,the population fluctuation crest of rice leaf roller and rice planthopper decreased,but the intensity increased with the advance of time,and the natural ecological regulation ability was relatively improved.[Conclusion]The sowing period of single cropping hybrid rice is delayed 5-10 d compared with conventional rice,that is,sowing in late May and early June.The seedling age of 20-30 d is beneficial not only to reduce the initial population quantity of rice leaf roller and rice planthopper in the field,but also to increase the population quantity of spiders.

Chemical Weeding in Dry Direct Seeding Fields of Single Cropping Middlelate Rice

Chemical weeding in dry direct seeding fields of single cropping middle-late rice was studied in Huida vegetable farm of Huizhou City in 2012. The main treatment was herbicide（ pretilachlor ＋ bensulfuron-methyl,Yangguo and butachlor）,and the sub-treatment was application method（ soil treatments,seedling treatment and integrated treatment）. The results showed that 80 g pretilachlor ＋ bensulfuron-methyl（ 36% pretilachlor ＋ 4% bensulfuron-methyl） diluted with 50 kg water could be sprayed or 200 g Yangguo（ 23. 9% butachlor ＋ 1. 1% bensulfuron-methyl） mixed with 15 kg sandy soil could be broadcasted per 667 m2 on the sowing day or the second day under moist condition of soil,which could effectively control weeds in dry direct seeding fields of single cropping middle-late rice.