| In recent years, apple tree canker occurred severely all over the apple production areasof Gansu and other provinces in China. Through studies on the investigation on main pestsand diseases of apple in Gansu Province, and researches on the pathogen morphology, theoccurrence regularity, the pathogenicity differentiation and host range of apple tree canker,besides, screening of chemical fungicides against apple tree canker in the laboratory, theresults of the studies were as follows:1. The kinds, distribution and incidence of main pests and diseases of apple in GansuProvince were investigated in2010and2011. The results showed that22kinds of diseasesand40kinds of pests were found in the total apple orchards investigated. Among all kindsof pests and diseases, Valsa mali, Alternaria mali, Marssonina mali, Gymnosporangiumyamadai, Tetranychus viennensis, Lithocolletis ringoniella, Aphis citricola, Pseudococcuscomstocki and Carposina niponensis occurred all over the apple production areas ofGansu, moreover, the average incidence of apple tree canker occurred more severely inTianshui, Pingliang, Qingyang and Longnan, reached30%. Alternaria mali andMarssonina mali occurred in Lanzhou, Baiyin, Tianshui, Pingliang, Qingyang, Longnanand Dingxi, especially in Qingyang and Pingliang. Tetranychus viennensis occurredmoderately in Tianshui, Pingliang, Wuwei and Qingyang. Eriosoma Lanigerum occurredmildly in Qingyang, Pingliang and Dingxi. Cydia pomonella, one quarantine insect,occurred mildly in Jiuquan, Jiayuguan and Zhangye.2.15regions of apple tree canker were researched morphologically with free handsection, microscopic observation, micro-measurement and inoculating branches invitro.The results showed that the teleomorph of apple tree canker existed inTianshui,Plingliang and Qingyang with the proportion23%,29%,8%. Buried depth ofascus chamber, infection of sexuality and biological characterwastics were researched inthree city, the results showed that buried depth of ascus chamber of pathogen fromPingliang was highest, with an average depth of809.85μm; Ascospores of the teleomorphwere not infectious to apple tree branches in vitro. Micro-measurement and pathogenicitytests on the anamorph showed that the teleomorph pathogen of apple tree canker in Gansuwas Valsa mali, and the anamorph pathogens of apple tree canker in Gansu wereCytospora mali and C.carphosperma.3.The peak time of occurrence, routes of transmission, the hibernacula andoccurrence-related factors of apple tree canker were investigated and researched in Lanzhou apple orchards. The results showed that there were two quantums of peak time,from February to May and from September to November. The overwintering form isdiseased survival, and the anamorph spores were isolated from the soil in the orchard. Themain routes of transmission were airflow and rainwater. Some relationship was foundbetween propagation distance and spores quantity, and it coincided with model ofy=-0.1229x+18.6. Apple varieties, tree vigor, tree age, planting density, fertility and watermanagements, pruning level and soil texture coincided with apple tree canker.4. The pathogenicity differentiation and host range of15strains of the anamorph weremeasured with inoculating branches in vitro.These strains showed obvious pathogenicitydifferentiation, Cytospora mali stronger than C.carphosperma. Strain PL-1showed thehighest pathogencity, but strain TS-6of Cytospora mali showed the lowest pathogencity.Strain TS-5of C.carphosperma showed lower pathogencity than the other strains.Different apple varieties showed different reactions to the pathogen incubation,Starkrimson was the weakest variety to resist the pathogen than any others, but'Fuji' wasthe stronger varity to resist the pathogen than any others. The branch test of poplar, pearand peach trees in vitro showed that poplar branches cannot be affected by the apple treecanker pathogen, but the pear and peach trees can be affected.5. The toxicity and control effects in laboratory of5fungicides, difenoconazole,propiconazole, Jun-du-tsing, tebuconazole and three iodine against apple tree canker inLanzhou was measured using plate growth rate method. The results showed that these5fungicides against apple tree canker showed some inhibition, and the higher theconcentration of these5fungicides, the stronger the antagonism of strain LZ-1.Theinhibition of difenoconazole against the growth of strain LZ-1mycelium was strongest.The inhibition of difenoconazole against the germination of strain LZ-1spores wasstrongest. These5fungicides showed different control effect on the disease spots ofinoculating branches in vitro by strain LZ-1pure culture biscuits, and three iodine showedthe best protection effect compared with other tested fungicides. |
