柑橘黑点病菌种群对代森锰锌的敏感性评价及其替代药剂的筛选
Sensitivity evaluation of Diaporthe citri populations to mancozeb and screening of alternative fungicides for citrus melanose control

为明确柑橘黑点病菌种群对代森锰锌的敏感性及筛选更高效的防治药剂，采用孢子萌发法测定来源于黄岩、衢州、梅州和南丰4个生产果园种群和1野生种群，共221个柑橘黑点病菌菌株对代森锰锌的敏感性；并在离体、温室和果园条件下，评价百菌清和克菌丹等药剂的抑菌活性和防治效果。结果显示，南丰种群和衢州种群对代森锰锌的EC50分别为1.11、1.01 μg/mL，显著高于野生种群0.90 μg/mL，但最不敏感菌株抗性水平仅为1.8，小于5；百菌清和克菌丹对孢子萌发抑制效果显著优于代森锰锌，温室防效与代森锰锌相当；苯醚甲环唑抑制孢子萌发效果显著低于代森锰锌、百菌清和克菌丹，但抑制菌丝生长的效果显著较好。代森锰锌与苯醚甲环唑以质量比4∶1混合对抑制菌丝生长有增效作用，与矿物油以1∶1 250及1∶6 250混合对抑制病菌孢子萌发有增效作用。结果表明我国柑橘黑点病菌种群仍对代森锰锌敏感，代森锰锌仍为有效防治药剂；添加适量苯醚甲环唑或矿物油有提升代森锰锌防效的潜力。
To investigate whether Diaporthe citri populations are still sensitive to mancozeb, and to screen more efficient fungicides for citrus melanose control, the sensitivity of 221 D. citri isolates of four commercial orchard populations and one wild population to mancozeb were tested by using the method of inhibition of conidial germination. The antifungal activities and control effect of the fungicides chlorothalonil and captan were assessed under in vitro, greenhouse, and field conditions. The results showed that the average EC50 values of Nanfeng or Quzhou population were 1.11 and 1.01 μg/mL, respectively, which was significantly higher than that of the wild population with an EC50 of 0.90 μg/mL. However, the resistance factor of the least sensitive isolate in this research was 1.8, less than 5. Chlorothalonil or captan had a better effect than mancozeb in inhibiting the conidial germination of D. citri. When applied as protectants before the inoculation, chlorothalonil, captan and mancozeb showed similar control effects against melanose. Though difenoconazole showed lower inhibitory effect against the conidial germination of D. citri, it had a higher inhibitory effect on mycelial growth than mancozeb, chlorothalonil and captan. When mancozeb and difenoconazole were mixed at the mass ratio of 4∶1, their synergistic effect on mycelial growth was exhibited in vitro. Mineral oil could increase the activity of mancozeb and synergistic effect against conidial germination was exhibited when mancozeb and mineral oil were mixed with the mass ratio of 1∶1 250 or 1∶6 250. Taken together, the populations of D. citri in China are still sensitive to mancozeb and mancozeb remains to be an efficient fungicide for melanose control. Adding a moderate amount of difenoconazole or mineral oil into mancozeb may further promote its control effect against citrus melanose.