The Fungicide Screening For Controlling Cotton Damping-off On The Level Of Anastomosis Group

Cotton damping-off is one of the more common cotton disease occurred in China. It is seriouslyaffecting the cotton production. The aim of the paper is to screen efficient fungicide of preventing disease.It will effectively control the occurrence and damage of the disease. Collected typical diseased plants ofcotton damping-off and soil samples from the cotton fields of the San ping and Shi Hezi in2012. Itobtained76strains of Cotton Rhizoctonia solani by the tissue isolation、directly soil separation andmorphological identification. Then it have done the anastomosis group determination on this basis and aseries of screening fungicide for each anastomosis group. Finally, screened two kinds of fungicide that havehigh virulence to major and all anastomosis groups of cotton Rhizoctonia solani. They can effectly controlthe Cotton damping-off It will lay a foundation for effectively controlling cotton damping off.Separation and purification results showed that：it is easy to obtained the strains of Rhizoctonia solanithat caused cotton damping-off by the tissue isolation and directly soil separation. The separation ratio thatisolated strains of Rhizoctonia solani from diseased plants was obviously higher than that of soil samples.Identification of different anastomosis group showed that: the anastomosis group of Rhizoctonia solaniconsists of AG1、AG2、AG4、AG5, which AG4is the major anastomosis group in cotton field (about58%in the number of anastomosis group’s strains).The inhibition zone test indicated that there are some differences about inhibition in the twelve kinds offungicide for controlling Cotton Rhizoctonia solani to the major anastomosis group (AG4), but there aresignificant differences in the size of inhibition. Tolclofos-methyl, GJJ, BL, Wei Fu, mancozeb andchlorothalonil have better inhibitory effect in twelve kinds of fungicide.Toxicity test results showed that the toxicity about nine kinds of fungicide against Rhizoctonia solani isremarkable, the toxicity that same fungicide to different anastomosis group also have some differences. Thefour kinds of fungicide (GJJ, tolclofos, BL and wei Fu.) in the nine kinds of fungicide have greater toxicityagainst the major and all anastomosis group (AG4), the EC50is less than3mg/L. The other five kinds offungicide is relatively small against the major and all anastomosis group (AG4). The toxicity that allfungicide to different anastomosis group of cotton damping-off are significantly different.Effectiveness in field verification showed that under the condition of intermediate value that usingfungicide recommended. Four kinds of fungicide have good control effect against cotton damping-off in thenatural state of field and artificial inoculation. The control efficiency between62%to85%. The controleffect of GJJ is best in four kinds of fungicide, tolclofos followed by. The control efficiency of the twofungicide is above80%in the condition of natural incidence. It plays an efficient role in preventing cottondamping-off.