| Wenzhou has a wide variety of old and valuable tree resources.With the rapid development of urbanization,some of the old and valuable trees in Ouhai District of Wenzhou are infested by pests and diseases,resulting in weakened growth,and the resources of old and valuable trees are under serious threat.This paper investigates the basic situation of old and valuable trees in Ouhai District,Wenzhou,collates the number of species,distribution,measurement factors,main pest and disease species,occurrence status and causes of occurrence,summarizes the problems and difficulties in the protection of old and valuable trees,and puts forward relevant suggestions.At the same time,we selected the coal stain,aphid and blackthorn fly,which have a greater impact on Ficus,to conduct efficacy tests to investigate the relationship between their occurrence and to screen out economically efficient and effective agents and combinations to provide a basis for guiding the protection and management of ancient trees in Ouhai District,Wenzhou.The main research is as follows:(1)The survey yielded a total of 563 old and valuable trees and reserve resources in Ouhai District,Wenzhou,belonging to 15 families and 20 species.Among them,232 are Ficus concinna,accounting for 41.21% of the total,followed by Liquidambar formosana and Castanopsis sclerophylla.At present,the normal growth of old and valuable trees is seriously affected due to the problems of propaganda and protection,management and supervision,and lack of protection measures in the competent departments and local streets.(2)The survey yielded a total of 49 species of pests and diseases in Ouhai District,including 12 diseases and 36 insect pests.The most frequent pests and diseases of Ficus are Sooty blotch,Aleurocanthus spiniferus and Aphids,and the occurrence of pests can cause infestation of Sooty blotch.The main reasons for the susceptibility of old trees to pests and diseases are weakened growth,poor environment and weak natural control.(3)The rate of population reduction of aphids with 20% bromoxynil suspension 1000 times was nearly 90%,and the infection rate and disease index of leaf coal stain were significantly controlled after aphid control: three lesser used insecticides,22% thiacloprid,20% bromoxynil and 12%mevinphos-methyl,were selected for aphid control trials,and it was found that 20% bromoxynil suspension 1000 times The best effect was achieved in the treatment group,with the remission rate of87.77% and the control effect reaching 90.86%.34 d after application,the infection rate and disease index of leaf coal stain were controlled below 5%.(4)The rate of population reduction of black spurge was nearly 90% with 22% thiamethoxam perchlorofluoride suspension 1000 times,and the infection rate and disease index of leaf coal stain were also significantly controlled after the control of black spurge: three insecticides,22% thiamethoxam perchlorofluoride,20% bromoxynil and 12% mevinphos-methyl,were selected for the control of black spurge,and the study concluded that 22% thiamethoxam perchlorofluoride suspension The best effect was obtained in the group treated with 1000 times of thiamethoxam fluoride suspension,with the rate of insect population reduction reaching 87.02% and the control effect reaching 89.36%,and the coal stain infection rate and disease index were controlled at about 5% 34 d after application.(5)There was no significant difference in the control effect of 95% mineral oil products produced by the two companies: for the presence of Ficus,95% mineral oil products from the two companies available in Wenzhou were selected at 500 and 800 times the concentration for the control of coal stain,and it was found that the control effect of the two mineral oils at the same concentration was close,with800 times of 95% mineral oil emulsion being more effective than 500 times.The control effect is better than 500 times.(6)Three mixtures of fungicides,mineral oil and washing powder were more than 90% effective in the control of coal stain: 30% benzyl-propiconazole emulsifiable oil,30% semimethomyl suspension,95% mineral oil and washing powder were selected to study the effect of single agent and mixed agent groups on the control of coal stain.Finally,among the seven groups of agents,the mixed agent group consisting of 30% benzyl-propiconazole emulsifiable oil or 30% semimethomyl suspension with 95%mineral oil emulsifiable oil and washing powder was selected to have the best decontamination effect on coal stain,with the highest infection rate and disease index control effect of 93.71% and 91.66%,respectively.In summary,this study proved that the control of black spurge and aphids can affect the infestation of coal stain,and two chemical insecticide agents and one chemical fungicide combination were screened for the three pests and diseases,which are expected to be used in the future protection of Ouhai District. |
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