棉 花 学 报    Cotton Science   2007，19(2)：93-97

Studies on Co-toxicity of the Mixed Preparations of Several Fungicides to Fusarium moniliforme
PAN Yue-min，GAO Zhi-mou^*，WANG Jing-xin，CAO Jun，WANG Tao
( College of Plant Protection，Anhui Agricultural University，Key Lab of Agro-food Safety of Anhui Province，Hefei 230036，China)

Abstract：Cotton red rot is an important disease of cotton in China. The disease seriously endangers cotton by causing the rot of buds，stem bases and roots of cotton at seedling stage，and resulting in boll rot in boll phase. Recently，the incidence and severity of the disease at both seedling and boll stages have been developing with the extending of the Bt-transgenic cotton in Anhui，China. To screen the effective fungicides for the control of the disease，EC₅₀ of seven kinds of fungicides and the co-toxicity of their mixed preparations to Fusarium moniliforme Sheld，the pathogen of cotton red rot，were tested by means of mycelium growth rate method under the condition of laboratory，respectively. The results showed that EC₅₀ values of prochloraz，triadimefon，difenoconazole，propiconazol and carbendazin were 0.0923，1.5604，1.7414，2.0602 and 2.7599mg·L^-1，respectively，suggesting that the five fungicides tested all had good inhibition against the fungus. But azoxystrobin and mancozeb were not obviously inhibitory against the pathogen，with the EC₅₀ value being 116.0600 and 521.0000mg·L^-1，respectively. On the basis of the experiments，the combined toxicity coefficients (CTC) and the synergistic effects of the mixtures of the five fungicides were investigated applying Sun & Johnson method，and the results indicated that the mixtures of difenoconazole and carbendazin had all significantly synergistic effect while the other mixtures had not. CTC values of the mixtures with the mixing ratio of difenoconazole to carbendazin as 2∶1，1∶1，1∶2，1∶3 and 1∶5 were 151，219， 154，208 and 140，respectively. The order of CTC values of the mixtures of difenoconazole and carbendazin with different mixing ratios of difenoconazole to carbendazin was CTC_1∶1>CTC_1∶3>CTC_1∶2> CTC_2∶1>CTC_1∶5. Among the five matching ratios，1∶1 matching ratio of difenoconazole and carbendazin had the best additive effect. However，since the cost of difenoconazole is much higher than that of carbendazin，the optimal matching ratio of difenoconazole and carbendazin was1∶3，considering both the synergistic effect and the economic benefits. In addition，it was observed that the mixtures of prochloraz and other fungicides tested and the mixture of difenoconazole and mancozeb had all obviously reductive effect on inhibiting the pathogen. Although azoxystrobin had evident inhibition against Fusarium moniliforme at the low concentration of 1 mg·L^-1，the inhibitive effectiveness did not increase with the rise of concentration of azoxystrobin，and there was no significant difference in the inhibitive effectiveness of the tested concentration treatments from 1 to 200 mg·L^-1. The reasons are worthwhile to probe further. The results mentioned above provide experimental evidence for the exploitation of new and effective fungicides or mixed preparations and for the reasonable application of the chemicals to control cotton red rot.
Key words：cotton；Fusarium moniliforme；fungicides；mixtures；co-toxicity；synergistic effect   [Full Text，1925KB]