Efficacy,Toxicity And Safety Evaluation Of Fungicide Compound 6AD

Plant diseases caused by pathogenic fungi such as Rhizoctonia solani,Fusarium graminearum,and Sclerotinia sclerotiorum can seriously threaten food safety and production.At present,chemical pesticides are still the main means to control plant diseases.However,excessive and unreasonable use of chemical pesticides also has a serious impact on the ecological environment and human health.In this context,the Ministry of Agriculture and Rural Affairs of China put forward the goal of"zero increase in pesticide use"to reduce the use of pesticides while ensuring the yield and quality of agricultural products.Therefore,the development of new fungicides with high efficiency,low toxicity and low residue,as well as the screening of synergistic formulations is very important to achieve this goal.The triazolyl hydrazide compound 6AD with significant bactericidal activity was obtained by the screening earlier in the laboratory.In this study,the indoor toxicity of 6AD against Rhizoctonia solani,Fusarium graminearum,Rhizoctonia cerealis and Sclerotinia sclerotiorum were tested.And in order to identify the compound combinations with significant synergistic effects,the combined toxicity of 6AD with some commercial fungicides such as prochloraz,tebuconazole,prothioconazole,boscalid and carbendazim was further investigated according to their EC₅₀ value;According to the‘Test Criteria for Environmental Safety Assessment of Chemical Pesticides’,the field acute toxicity tests of6AD to non-target organisms such as bees,birds,silkworms,earthworms,fish,etc.,were carried out.The toxicity of 6AD to organisms in the environment was determined based on the measured LD₅₀(LC₅₀)values.According to the‘Laboratory Test Criterion for the Safety of Bactericides and Insecticides on Crops’,the effects of 6AD on wheat germination rate,emergence of seedlings and the symptoms of pesticide injury in each growth period were studied,so as to determine the safety of 6AD on crops.The results of this study are as follows:1.The results of the bioassay showed that the median inhibitory concentration(EC₅₀value)of 6AD against Rhizoctonia solani,Fusarium graminearum,Rhizoctonia cerealis,Sclerotinia sclerotiorum were 0.110 mg/L,0.414 mg/L,2.832 mg/L and 0.707 mg/L respectively.For Rhizoctonia solani,when 6AD was mixed with prothioconazole in the ratio of 4:1,the EC₅₀ value was 0.072 mg/L and the co-toxicity coefficient value was 179.8.When6AD was mixed with tebuconazole in the ratio of 4:1,the EC₅₀ value was 0.063 mg/L and the CTC value was 162.9.When 6AD was combined with carbendazim at the ratio of 1:4,the EC₅₀ value was 0.125 mg/L,and the CTC value was 123.4.For Fusarium graminearum,when 6AD and prochloraz were mixed at the ratio of 5:5,the EC₅₀ value was 0.035 mg/L and the CTC value was 372.1.When 6AD was mixed with prothioconazole at the ratio of 4:1,The EC₅₀ value was 0.107 mg/L and the CTC value was 466.9.When 6AD was mixed with carbendazim at the ratio of 4:1,the EC₅₀ value was 0.292 mg/L and the CTC value was 140.1.For Sclerotinia sclerotiorum,when 6AD was mixed with tebuconazole at the ratio of 1:4,the EC₅₀ value was 0.078 mg/L and the CTC value was 121.2.The combined effects of the above agents were all synergistic effects,and these compound combinations with obvious synergistic effects could greatly improve the antifungal effects of 6AD against pathogenic fungi.This experiment also found that the compound combinations in the same compound ratio had good activities against multiple pathogenic fungi.2.The results of environmental non-target biological acute toxicity test showed that the acute oral LD₅₀（48 h）of 6AD to Apis mellifera L was 61.2μg a.i./bee,and the acute exposure LD₅₀（48 h）of 6AD to Apis mellifera Lwas more than 100μg a.i./bee,indicating that 6AD has low toxicity to Apis mellifera L.During the experiment,some bees in the high concentration treatment group showed abnormal symptoms,such as tremble,slow movement,body crouching and so on.The acute toxicity LD₅₀（14 d）of 6AD to Eisenia foetida was more than 100 mg a.i./kg _{dry soil},indicating that 6AD has low toxicity to Eisenia foetida,and earthworms did not show abnormal symptoms in soil containing 6AD liquid.The acute toxicity LD₅₀（7 d）of 6AD to Coturnis coturnix japonica was more than 500 mg a.i./kg _{body weight},indicating that 6AD has low toxicity to Coturnis coturnix japonica.Abnormal symptoms such as vomiting appeared in birds after being fed high concentration of 6AD solution,but no death occurred.The acute toxicity LC₅₀（96 h）of 6AD to Bombyx mori was more than 2000 mg a.i./L,indicating that 6AD has low toxicity to Bombyx mori,and no abnormal symptoms appeared after the silkworms were fed mulberry leaves soaked with 6AD solution.The acute toxicity LC₅₀（96 h）of 6AD to Brachydanio rerio was 0.853 mg a.i./L,indicating that 6AD has high toxicity to Brachydanio rerio.These results indicate that 6AD has low toxicity to non-target terrestrial organisms and high toxicity to fish.Therefore,when applying 6AD,attention should be paid to avoiding the special period of aquatic animals,so as to reduce the harm of chemical pollutants to aquatic animals in the field.However,for dry field crops,6AD can be used for plant disease control.3.The results of wheat crop safety experiment showed that soaking wheat seeds with6AD at 100 mg/L and 50 mg/L had no effect on the germination of wheat seeds,but it had a certain effect on the growth of wheat seedlings and roots,indicating that soaking wheat seeds with 6AD had a certain inhibitory effect on the growth and development of wheat seeds.The effects of 6AD at 100 mg/L and 50 mg/L on wheat emergence and growth were measured.It was found that the emergence rate of the test groups was significantly different from that of the blank control.During the test period,the growth of the wheat seedlings was the same,and there was no pesticide injury.As a result,6AD can be used as a fungicide to control pathogens of wheat crops.