Investigation,Pathogen Identification And Control Of Kiwifruit Leaf Spot Diseases In Jiangshan City

Kiwifruit is an important cash crop with a long history of cultivation in China.As the"hometown of kiwi in China",Quzhou Jiangshan has continuously expanded its industry scale and kiwifruit has become a"golden fruit"for increasing income and wealth.However,in recent years,kiwifruit diseases have become increasingly harmful,especially leaf spot disease,which seriously affect the yield and quality of kiwifruit.At present,there is no conclusive conclusion on the identification of the pathogen of kiwifruit leaf spot disease at home and abroad,and there is no report on the occurrence of kiwifruit disease in Jiangshan City.Therefore,this study investigated the occurrence of kiwifruit disease and the characteristics of leaf spot disease in Jiangshan City,collected samples of kiwifruit leaf spot disease from different areas of Zhejiang Province,identified the pathogen through pathogen isolation and purification,pathogenicity testing,combined with morphological observation and molecular biological techniques,and carried out laboratory toxicity determination and field efficacy trials.It is expected to provide a theoretical basis for the rational selection of fungicides and comprehensive control of kiwifruit leaf spot disease in agricultural production.The main results of this study are as follows:1.Identified the occurrence of major diseases of kiwifruit in Jiangshan City.The occurrence of diseases in the main planting areas of kiwifruit in Jiangshan City was investigated through fixed and random sampling survey and visiting investigation.The results showed that the main diseases of kiwifruit in Jiangshan City include canker,leaf spot,anthracnose,black spot,soft rot,gray mold and flower rot.There were significant differences in the incidence of disease,among which the most serious diseases were canker and leaf spot.2.The occurrence characteristics of kiwifruit leaf spot disease in Jiangshan City were preliminarily confirmed.Through random sampling to select field,according to the double diagonal five sampling method to investigate the occurrence of leaf spot.The results showed that the incidence of leaf spot disease became more serious with the increase of temperature,and the disease index decreased with the increase of altitude.The occurrence degree of leaf spot of different varieties varied greatly,and the incidence rate and disease index of Hongyang were higher than those of Xuxiang.3.Identified the pathogen fungi of kiwifruit leaf spot disease.In this study,the diseased leaf samples were randomly collected from Jiangshan,Zhejiang Province.According to the tissue isolation method,60 strains were isolated from diseased leaves,mainly including Alternaria sp.,Phomopsis sp.,and Colletotrichum sp.,with isolation frequencies of 41.6%,20%,and 8.3%,respectively.23 strains of Alternaria were isolated,cultured,and purified.By observing their morphological characteristics and molecular biology identification based on ITS gene and Histone 3 gene,it was determined that the main pathogenic fungus causing kiwifruit leaf spot disease were Alternaria fungi,including two species,Alternaria alternata and Alternaria tenuissima,with the dominant species being A.tenuissima accounted for 65.22%.The results of pathogenicity testing showed that both strains of Alternaria could cause disease after stabbed inoculation into healthy leaves.At the same time,the difference of pathogenic fungus on kiwifruit leaf spot disease with different symptoms was clarified.4.Effective Chemical fungicides for controlling kiwifruit leaf spot disease were screened out.Using A.alternata and A.tenuissima as the research objects,the indoor toxicity of trifloxystrobin,fluopyram,difenoconazole,and mancozeb was determined using the mycelial growth rate method.The results showed that all four fungicides could inhibit the mycelial growth of two species of Alternaria fungi,and the higher the concentration of the fungicide,the more obvious the inhibitory effect.The order of toxicity to A.alternata from high to low was fluopyram,trifloxystrobin,mancozeb and difenoconazole,with EC₅₀values of 5.760μg/m L,16.834μg/m L,19.087μg/m L and 38.776μg/m L,respectively.The order of toxicity to A.tenuissima from high to low was fluopyram,trifloxystrobin,difenoconazole and mancozeb,with EC₅₀values of 3.805μg/m L,9.033μg/m L,24.9μg/m L and 29μg/m L,respectively.Field efficacy trials showed that 43%fluopyram·trifloxystrobin（SC）had the best control effect on kiwifruit leaf spot disease among the four tested fungicides,and the control effects of the three concentrations treatments all reaching over 80%.The control effects of 2000 times liquid,3000 times liquid and 1500 times liquid were 86.05%,83.57%and 80.30%,respectively.In field experiments,the control effect of 80%mancozeb（WP）600 times liquid was 69.93%,the control effect of 50%iprodione（WP）1000 times liquid was 51.27%,and the worst control effect was 10%difenoconazole（WG）1500 times liquid,with a control effect of 50.84%.