Study On Integrated Control Technology Of Broccoli Clubroot

In recent years,the occurrence of broccoli clubroot was increasing year by year in Taizhou City,Zhejiang Province.By field investigations,the occurrence situation,infection source and infection route were clarified.Field experiments of different fungicides were carried out to determine the effect of different dosage,applied period and times on clubroot.The safety of fluazinam on broccoli at seeding stage was clarified.The cost-saving and efficiency-increasing synergistic techniques during fluazinam application were discussed.In addition,the broccoli varieties with high resistance to clubroot were obtained by screening.The main results were as follows:1)Agricultural control techniques of broccoli clubrootAccording to the results of investigations on broccoli clubroot in Taizhou,the available agricultural measures mainly included:cleaning up and centralized incineration of the diseased plants;rotation with non-cruciferae crops;avoiding flood irrigation to reduce soil moisture;Using aseptic substrates,washing and disinfecting the recycled plugs;cultivating healthy and strong seedlings.2)Screening fungicides and study on control techniques for broccoli clubroot500 g/L Fluazinam SC was the best one to control the broccoli clubroot among the five fungicides.It was suggested that the effective dose(the same below)was 2 250 g/hm~2 by irrigating roots twice,and the periods of irrigating roots were at 3～7 d and 30 d after transplanting,with 150 m L per plant of liquid volume every time.The second was 100 g/L cyazofamid SC.The control effect was good with the dose of 338 g/hm~2 by irrigating roots twice at 0～3 d and 30 d after transplanting,but not as good as fluazinam,which the difference was significant.The control effect of 75%chlorothalonil WP 8 440 g/hm~2was similar with that of 100 g/L cyazofamid SC 338 g/hm~2.However,20%zinc thiazole SC and 62.5 g/L metalaxyl-M·fludioxonil FS were not good,which were not suitable for controlling broccoli clubroot.3)Safety analysis of fluazinam on broccoliThe improper use of fluazinam had the risk of drug damage,which was related to the dose and the period of root irrigating.The plant height and leaf area were inhibited,and the maturity of the flower head was delayed to varying degrees with the treatments of 500 g/L fluazinam SC 2 250,3 375,4 500 g/hm~2applied at 0,3,3 days after transplantation,respectively.As the dose higher and the irrigating period earlier,the damage showed more serious.Especially in the seedling stage,the use of fluazinam could obviously inhibit the growth,with short plants,yellow leaves and improperly packed roots,but there wasn’t significant effect on germination rate.4)Study on the control effect of different irrigating amount of fluazinam on broccoli clubrootThree days after transplantion,the broccoli roots were irrigated with the mixture of fertilizer and 500 g/L fluazinam SC 2 250 g/hm~2.The amount of water was more than five times of that of conventional application and the dilution multiple was too high to reduce the control effect of fungicide.It was necessary to increase the dose by 50%to achieve the effect of conventional irrigation.However,the cost of labor and gasoline could be reduced by half with the combined application of fungicide and fertilizer,and the total cost was 40yuan/hm~2 more than that of the conventional treatment.If the mixture of fluazinam and fertilizer was irrigated with large amount of water,it was suggested that the dose of fluazinam should be increased.5)Comparison of the control effect of two fluazinam products on broccoli clubrootUnder the same dose and control method,40%fluazinam SC and 500 g/L fluazinam SC had similar control effect,but the cost of 40%fluazinam SC was 25%lower than that of500 g/L fluazinam SC.It was recommended to use 40%fluazinam SC.6)Effect of alginic acid on fluazinam against broccoli clubrootThe addition of alginic acid to 500 g/L fluazinam SC had no obvious effect on the control of broccoli clubroot,but could promote the plant growth,which was reflected in the increase of plant height and leaf area,and early growth period.But there was no significant difference between alginic acid 1 500 g/hm~2 and 2 250 g/hm~2 in promoting growth.7)Varieties of broccoli resistant to clubrootYacui 91 was a mid-late maturing broccoli variety,and showed high resistance to clubroot and had excellent comprehensive agronomic characters.It could be planted as a disease-resistant variety in Taizhou City,Zhejiang Province.