On Screening Of Effectual Fungicides And Mixed Preparations For Controlling Rapeseed Sclerotinia Stem Rot

Sclerotinia sclerotiorum is a kind of pathogenic fungi with many hosts, dangerous to 383 kinds of plants in 64 families. It belongs to ascomycotina fungus and causes rapeseed sclerotinia stem rot, a worldwide disease, mainly in oilseed rape growth relatively cold and humid regions. In Asia winter rapeseed area, the disease is more serious. General incidence is from 10% to 30%, even over 80%. Because of the disease, the rapeseed yield is decreased by 10%～70%, and the crude fat content is reduced by 1%～5%. Obviously, the disease seriously affect the yield and quality of rapeseed. At present, the prevention and control of the disease is still chemical control, and the main fungicide has been broad-spectrum fungicide carbendazim. Due to the long-term use of carbendazim for chemical control, the severe resistance of the fungus has developed in many areas in Anhui. In order to overcome and delay the development of drug resistance in the population of S. sclerotiorum, we should avoid the single use of carbendazim, and should apply it with other types of fungicides or mixtures. Therefore, the screening of effective fungicides and mixed preparations for cotrolling rapeseed sclerotinia stem rot was investigated in this paper. The main results of the study are as follows:1. Using the method of mycelial growth inhibition, the toxicity of the 7 kinds of fungicides agaist S. sclerotiorumwas was tested in vitro. The results showed that the order of EC50 values of 7 kinds of fungicides was:kresoxim-methyl> carbendazim> prochloraz> prochloraz> dimethachlon> the fanniemae and freddie MAC> tebuconazole> procymidone. The toxicity of procymidone was the strongest, with EC50 of 0.1524 mg·L-1, and others were decreased in turn, with kresoxim-methyl being minimum.2. The joint toxicity of prochloraz with the carbendazim was investigated by applying Sun Yunpei’s cotoxicity coefficient method. The results showed that the mixture of the two kinds of single chemicals, prochloraz and carbendazim, had a synergy. So the two fungicides, prochloraz and carbendazim were selected for farther experiment of mixed preparation. The experiments of mixed preparation indicated that of the mixture has obvious synergy when prochloraz was mixed with carbendazim according to the ratio of 1:0.5 to 1.5, However, the mixture of prochloraz and carbendazim showed antagonism when increases the rate of carbendazim,. And the results in field experiments showed that the control effectiveness of the mixture of the two fungicides in the ratio of 1:1.5 to the disease was up to 85%. Based on the above results and giving attention to the cost, the ratio of 1:1.5 for the two fungicides was appropriate.3. By means of the random block design, the field experiment of the biological agent, the wettable powder of shield shell mould (4 billion spores/g) for controlling rape sclerotinia stem rot was conducted, and the results showed that at the dosage of 90 g/667m2, the control effectiveness of the biological preparation was 76.72%, which was be superior to that of carbendazim, the contrast.