粉锈宁和羟锈宁拌种防治玉米丝黑穗病几种影响药效和药害的因子研究

粉锈宁和羟锈宁拌种防治玉米丝黑穗病的田间试验表明,墒情影响药效,墒情好,药效高。正常低土温和正常高墒情相结合,可以达到既压低发病基数,又获得高防效的双重目的。粉锈宁和羟锈宁的防效是近似的。墒情对羟锈宁的影响似更敏感,其防效的稳定性较粉锈宁差,但羟锈宁对幼苗的抑制轻,在逆境下造成的药害小。两种药剂的胶悬剂并不比可湿性粉剂优越。乳剂防效稍高,但药害较重。与促进生长的激素浸种结合应用有降低药效的趋势,不宜采用。室内试验证明,过饱和墒、过低土温和厚复土三者结合是田间按常用量拌种有时造成药害的原因。药害主要发生在干种至种子开始萌动阶段。玉米自交系的抗药性比杂交种差,应用药剂拌种时尤需慎重。

STUDIES ON THE FACTORS RELATED TO THE EFFECTIVENESS AND PHYTOTOXICITIES OF THE SEED-DRESSING-FUNGICIDES, BAYLETON® AND BAYTAN® FOR CONTROLLING THE HEAD SMUT ON COR

Investigations were carried out in the laboratory and in the orchard-plots to determine several factors which were influence the effectiveness and phytotoxicities of Bayleton^® and Baytan^® for controlling the head smut of corn by seed-dressing.The results obtained indicated that the effectiveness of these fungicides were affected by soil moisture, the higher the soil moisture, the better the control of the disease.Baytan^® was found to be more sensitive to the soil moisture but lesser in phytotoxicity than Bayleton^®.Owing to the formulations of the fungicides, cmulsion concentration provided better cotnrol but resulted in serious, phytotoxicity, whereas colloidal suspension and wettable powder were about the same which providing a moderate control but lesser phytotoxicities.These fungicides should not be applied simutaneously with any growth promotive hormone, since decreasing persistence of the fungicides by the plant hormone was found.Phytotoxicities were observed occasionally in the field in the cooler-rainy seasons. Laboratory tests demonstrated that the combination of higher soil moisture, lower soil temperature and thicker soil coverings caused more phytotoxicity. Onset of germinating seeds were the most critical period on the phytotoxicity and the inbred lines of corn were less resistant caution should be taken.