氟乐灵土壤处理对棉花苗期病害的影响

Effect of trifluralin-treatment on cotton seedling diseases:

平板试验中,氟乐灵在有效成分2～10μg/ml 的浓度下,对棉立枯病菌(Rhizoctoniasolani)、棉猝倒病菌(Pythium aphanidermatum)和棉红腐病菌(Fusarium moniliforme)的菌丝生长无明显的抑制作用.温室盆栽试验中,以有效成分2mg/kg 土的剂量混入或混合接种上述病菌的灭菌土中可提高棉苗的出苗率,减少由 R.solanit 和 P.aphanidermatum 引起的烂籽,减轻出苗后立枯病的发病率,但对减轻棉苗红腐病发病率的作用不明显,田间试验以175m1/亩(1亩≈666.7m^2,下同)的剂量能减轻棉苗立枯病和猝倒病的发生。但红腐病略有加重。氟乐灵播前作土壤处理,出苗后1周接种病原菌的试验中,处理组棉苗立枯病和猝倒病发病率显著减轻,但红腐病的发病率无明显变化.

In pure culture,no obvious inhibition of treating trifluralin on the hyphal growth of Rhizoctonia solani,Pythium aphanidermatum and Fusarium monUtforme was observed,when the com- pound was incorporated into the culture media at 2-10 μg a.i/ml.Results from greenhouse and field tests indicated that the emergences of trifluralin-treated groups were higher than those of untreated ones, due to their reduced rate of seed rot caused by R.so/an/and P.aphanidermatum,Moreover,the disease in- cidences and the rate of dead seedling caused by the two fungi at the seedling stage also decreased.How- ever,the disease incidence of Fusarium seedling rot caused by F.moniliforme was increased slightly by presowing treatment of soil with trifluralin.If the 7-day-old seedlings grown in trifluralin-treated soil were transplanted into trifiuralin-free soil and inoculated with the pathogens,the disease incidences caused by R.so/anl and P.aphanidermeatum in trifluralin-treated groups were significantly decreased,but the disease incidence caused by F.moniliforme was similar to the control.It was suggested that the presowing treatment of soil with trifluralin enhanced resistance of cotton seedlings against the diseases caused by R.solani and P.aphanidermatum.