不同杀菌剂对黄瓜靶斑病菌的毒力作用特性比较

为筛选防治黄瓜靶斑病的有效药剂，采用菌丝生长速率法、孢子萌发法和芽管伸长法测定了19种杀菌剂对黄瓜靶斑病菌的毒力，探究了4种毒力较高杀菌剂对病原菌菌丝形态的影响。结果表明:氟啶胺、吡唑萘菌胺、咯菌腈和四霉素对黄瓜靶斑病菌菌丝生长、孢子萌发和芽管伸长各生长发育阶段均有较强的抑制活性，其中，4种药剂抑制菌丝生长的平均EC₅₀值分别为0.516 3、1.538、1.605和0.648 2 mg/L，抑制孢子萌发的平均EC₅₀值分别为0.164 4、1.359、1.127和0.002 5 mg/L，抑制芽管伸长的平均EC₅₀值分别为0.189 6、0.144 7、0.060 4和0.001 5 mg/L；啶酰菌胺、百菌清和肟菌酯3种不同作用机制杀菌剂对黄瓜靶斑病菌孢子萌发和芽管伸长的抑制活性较强，3种药剂抑制孢子萌发的平均EC₅₀值分别为1.564、0.373 0和0.021 3 mg/L，抑制芽管伸长的平均EC₅₀值分别为0.629 5、0.233 4和0.405 0 mg/L，但对菌丝生长的抑制作用较弱，平均EC₅₀大于16 mg/L；氟啶胺、吡唑萘菌胺、咯菌腈和四霉素可引起黄瓜靶斑病菌菌丝不同程度的异常生长，主要表现为菌丝隔膜间距变小、菌丝节间肿大、主菌丝上二次分枝发生频繁、菌丝变形黏连、菌丝新分枝处生长受抑制或分生孢子生长变形。研究表明，氟啶胺、吡唑萘菌胺、咯菌腈和四霉素对黄瓜靶斑病菌具有较高的毒力，在黄瓜靶斑病的田间防治中具有较好的开发应用潜力。

Comparison of toxicity properties of different types of fungicides against Corynespora cassiicola on cucumber

In order to discover highly effective fungicides against Corynespora cassiicola on cucumber, the inhibitory activities of 19 fungicides against mycelial growth, spore germination and germ tube elongation of C. cassiicola were measured. The effects of the 4 selected effective fungicides on mycelial and conidial morphology were also evaluated. The results showed that fluazinam, isopyrazam, fludioxonil and tetramycin exhibited strong inhibitory activities against mycelial growth, spore germination and germ tube elongation at each growth stage of C. cassiicola. The average EC₅₀ value of the four fungicides for inhibiting mycelial growth were 0.516 3, 1.538, 1.605 and 0.648 2 mg/L, respectively. The average EC₅₀ value of inhibiting the spore germination were 0.164 4, 1.359, 1.127 and 0.002 5 mg/L, respectively. The average EC₅₀ value of inhibiting germ tube elongation were 0.189 6, 0.144 7, 0.060 4 and 0.001 5 mg/L, respectively. Fungicides with different modes of action, such as boscalid, chlorothalonil and trifloxystrobin, showed high efficacy against spore germination and tube elongation of C. cassiicola. The average EC₅₀ value of three fungicides to inhibit the spore germination were 1.564, 0.373 0 and 0.021 3 mg/L, respectively. The average EC₅₀ value of inhibiting the germ tube elongation were 0.629 5, 0.233 4 and 0.405 0 mg/L, respectively. But the inhibitory activities against mycelial growth were poor, the average EC₅₀ value were greater than 16 mg/L. After the treatment of fluazinam, isopyrazam, fludioxonil or tetramycin, the morphology of mycelial and conidia was studied. The microscopical observation showed that the mycelial septa spacing decreased, the edge of diaphragm appeared as intumescent and two branches of the main mycelia frequently occurred. In addition, mycelia became distorted and adhesive, the new branches of mycelium were inhibited or conidial growth was metamorphotic. Given that fluazinam, isopyrazam, fludioxonil and tetramycin showed excellent inhibitory virulence against C. cassiicola, these fungicides are potential candidates for the control of C. cassiicola in the field.