河北省黄瓜霜霉病菌对甲霜灵和嘧菌酯的抗性动态及七种药剂的田间防效
Resistance dynamics of Pseudoperonospora cubensis to metalaxyl and azoxystrobin and control efficacy of seven fungicides against cucumber downy mildew in Hebei Province

为明确黄瓜霜霉病菌对甲霜灵和嘧菌酯的抗性动态及相应药剂对黄瓜霜霉病的田间防效，采用叶盘漂浮法监测了2011-2015年河北省黄瓜霜霉病菌对甲霜灵和嘧菌酯的抗性，采用茎叶喷雾法测定了含甲霜灵或精甲霜灵的混剂及嘧菌酯单剂等7种药剂的田间防效。结果表明：采自河北省不同地区的838株黄瓜霜霉病菌对甲霜灵和嘧菌酯普遍产生抗性，抗性频率为100.00%，抗性倍数为482.99和354.97，黄瓜霜霉病菌对甲霜灵和嘧菌酯的抗性随着监测地区和监测年限而波动，唐山、沧州、石家庄、衡水、廊坊和保定市的菌株对甲霜灵和嘧菌酯的抗性指数高于其它地区，黄瓜霜霉病菌对甲霜灵和嘧菌酯的抗性指数在不同年度间高位波动。按照田间推荐剂量喷施，250 g/L嘧菌酯悬浮剂对黄瓜霜霉病的防效为72.15%~74.13%；68%精甲霜灵·代森锰锌水分散粒剂和58%甲霜灵·代森锰锌可湿性粉剂的防效分别为65.30%~70.19%和63.26%~68.35%，与80%代森锰锌可湿性粉剂防效相当；50%烯酰吗啉可湿性粉剂、250 g/L双炔酰菌胺悬浮剂和687.5 g/L氟吡菌胺·霜霉威盐酸盐悬浮剂的防效达82.00%以上，对黄瓜霜霉病具有较好的防效，在黄瓜霜霉病菌对嘧菌酯、甲霜灵和精甲霜灵产生抗性的地区，可作为替代或混配药剂使用。
In order to clarify resistance dynamics of Pseudoperonospora cubensis to metalaxyl and azoxystrobin and control effects of fungicides containing metalaxyl and azoxystrobin against cucumber downy mildew, the resistance to metalaxyl and azoxystrobin in 838 P. cubensis strains collected from different areas of Hebei Province from 2011 to 2015 was measured by using the leaf disc floating method, and the control efficacies of seven fungicides including azoxystrobin 250 g/L SC and metalaxyl· mancozeb 58 WP or mefenoxam·mancozeb 68 WG against cucumber downy mildew were assayed in the field with the method of spraying stems and leaves. The results showed that the resistance to metalaxyl and azoxystrobin widely occurred in all 838 P. cubensis strains with resistance frequency up to 100.00%. The resistance factors to metalaxyl and azoxystrobin were 482.99 and 354.97, respectively. The resistance frequency and resistance index fluctuated over areas of monitoring and years of monitoring, the resistance index of strains from Tangshan, Cangzhou, Shijiazhuang, Hengshui, Langfang and Baoding were higher than those from the other areas of monitoring in Hebei Province, and the index of resistance were at the high levels. The field trials of fungicides were performed at the recommended doses. Control efficacy used for the field of azoxystrobin 250 g/L SC was 72.15%-74.13%; control efficacy of mefenoxam·mancozeb 68 WG and metalaxyl·mancozeb 58 WP were 63.26%-70.19%, equivalent to or poorer than control efficacy of mancozeb 80 WP, the poor performance of azoxystrobin 250 g/L SC and metalaxyl·mancozeb 58 WP or mefenoxam·mancozeb 68 WG against cucumber downy mildew may be due to development of resistance to azoxystrobin, metalaxyl or mefenoxam; control efficacies of dimethomorph 50 WP, mandipropamid 250 g/L SC and fluopicolide·propamocarb hydrochloride 687.5 g/L SC were more than 82.00%, which could be used singly or in mixtures with the other fungicides for control of cucumber downy mildew in the areas where development of