Antifungal Spectrum And Control Effect Of Isopyrazam To Cucumber Powdery Mildew

Isopyrazam, which belongs to the succinate dehydrogenase inhibitors (SDHIs), was developed and patented by syngenta crop protection. In order to clarify the fungicide spectrum, this study determined toxicity of isopyrazam to23common pathogens using bioassay method. Meanwhile, the action mode of isopyrazam to cucumber powdery mildew was also intensively studied, the efficacy lasting period of that and systemic translocation of isopyrazam in cucumber plant were also ascertained by measuring. The purpose of this study is that agents in the field to be able to provide a reference for scientific use. The results were detailed as below:1. Isopyrazam has more favorable inhibition activity on Corynespora cassiicola, Colletotrichum orbiculare, Colletotrichum capsici, Alternaria solani, Alternaria mali, Phytophthora capsici, Phytophthora infestans, Botrytis cinerea, Sclerotinia sclerotiorum, Pyricularia oryzae and Macrophoma kawatsukai, of which EC50values ranged from0.1001to9.5175μg/mL; Isopyrazam has higher activity on the spore germination of Sphacelotheca reiliana, Aspergillus niger and Botrytis cinerea, its EC50values were0.0029μg/mL,0.0687μg/mLand1.3804μg/mLrespectively; It also has higher activity to S. fuligieca, and the EC50values were0.039μg/mL. Fluopyram exhibited high inhibition activity on Corynespora cassiicola, Alternaria solani, Alternaria mali, Botrytis cinerea, Sclerotinia sclerotiorum, Marssonina coronaria, Aspergillus niger and S. fuliginea, similar to that of isopyrazam. It is indicated that isopyrazam has a wider spectrum than fluopyram, and the former is equal or even higher to the later on antifungal activity.2. Assess the activity of isopyrazam against cucumber powdery mildew using cotyledons bioassay, we found that isopyrazam had favorable protective and curative effects to cucumber powdery mildew, with the EC50being0.039μg/mL and0.0497μg/mL respectively, slightly higher than that of fluopyram and apparently higher than that of hexaconazole, difenoconazole, pyraclostrobin, kresoxim-methyl and azoxystrobin.3. It confirmed that isopyrazam had good effect on protection, curation, eradication and anti-sporulation to S. fuligieca with the test of inoculation and treatment at different time. Isopyrazam with the concentration0.5μg/mL could inhibit the conidia gramination, mycelial growth and damaged the formed conidiophore, which influenced the formation of conidia.4. Isopyrazam showed strong systemic translocation in cucumber plant, especially its cross-layer conductivity, transverse conductivity and absorption from the roots to the shoots conduction transport capacity. The control efficacy of cross-layer translocation and transverse translocation with isopyrazam60μg/mL in cotyledons were94.40%and88.96%respectively. The control efficacy of cross-layer translocation and transverse translocation in leaves was95.26%and82.83%respectively. However, the basipetal uptake translocation was not apparent, the control efficacy of acropetal uptake and basipetal uptake translocation was16.54%and1.50%respectively.5. Indoor pot experiment results showed that isopyrazam60μg/mL exhibited long lasting efficacy to cucumber powdery mildew, with2to3weeks longer than that of triazoles and strobilurins. The treatment of isopyrazam60μg/mL began to show disease spots until28days after fungicide application. Moreover, its high control efficacy was observed even35days after treatment. But it’s quite different from hexaconazole30μg/mL, which showed significant decrease in control efficacy only14days after treatment.7days after treatment by difenoconazole100μg/mL, pyraclostrobin150μg/mL, kresoxim-methyl150μg/mL and azoxystrobin337.5μg/mL application, powdery mildew occurred.21days after pyraclostrobin150μg/mL, kresoxim-methyl150μg/mL and azoxystrobin337.5μg/mL application, that nearly showed no control efficacy.6. Field trial results showed that the control efficacy of isopyrazam to cucumber powdery mildew was the best, followed by fluopyram.10days after treatment, the control efficacy of isopyrazam60a. i. g/hm and fluopyram60a. i. g/hm to cucumber powdery mildew was93.83%and92.10%.20days after treatment, the control efficacy of isopyrazam60a. i. g/hm2and fluopyram60a. i. g/hm2could still be90.83%and89.05%respectively. Both higher than that of hexaconazole, difenoconazole, pyraclostrobin, kresoxim-methyl and azoxystrobin, they also showed long lasting efficacy.