Identification Of Newly Occurring Harmful Mites In Northern Local Orchard And The Effects Of Different Plants On Their Growth,Development And Reproduction

In recent years,we have discovered a pest mite in an open field orchard in Jining,Shandong,which has caused serious damage to pear trees.The mite also occurs on apple trees,peach trees,grapes and other fruit trees in orchards,but the occurrence is not large.In addition,the damage of this mite is also found on apple,cherry,crabapple and other fruit trees and landscaping plants in Tai’an and other places.The morphology of this mite is different from any common orchard pest mite species in the north.This study combines morphological observation and DNA barcode technology to identify the newly emerging harmful mites,and uses age-age gender life table theory to study and compare the mites feeding on different plants（pear,apple,peach and crabapples）The biological parameters and population ecological parameters（net multiplication rate R₀,intrinsic growth rate r,weekly growth rateλ,average generation cycle T）are the effective prevention and control of this mite and its damage to different fruit trees and garden plants.Forecast provides a basis.The test mites were collected from pear trees in Jining,Shandong,and were raised indoors.The various mites were observed under a dissecting microscope,and glass slide specimens of male adult mites were made and observed under a microscope.The results showed that the morphology of the mite was similar to Panonychus citri is highly similar.For further confirmation,the COI,ITS1,and ITS2 gene sequences of the mite were amplified and determined.After comparison and analysis,it was found that the sequences of these three genes are almost identical to the corresponding sequences of P.citri,and the homology is as high as COI（100%,100%,100%）,ITS1（99.67%,99.83%,and 99.83%）,ITS2（99.40%,99.11%,98.96%）;in a system based on 3 gene sequences On the developmental tree,new harmful mites clustered in the same clade with P.citri with 99%,94%,and 98%confidence.The morphological and molecular identification results showed that the pest mite that occurred in the open field orchard in Jining,Shandong was P.citri.Using the age-age life table theory,under the conditions of a temperature of 25±1℃,a relative humidity of 75%±5%,and a photoperiod of 16L:8D,we studied the presence of P.citri collected from pear trees in pear trees and apples.The growth,development and reproduction status of Peach,Peach and crabapples.The result is that the growth,development and reproduction of P.citri collected from pear trees on pear,peach,apple and crabapples show certain differences.The egg period was 3.74 d（Pear）,3.86 d（Peach）,4.14d（Apple）,and4.44 d（Crabapples）.The egg period on pear and peach trees was significantly shorter than that of the other two hosts.There was no significant difference in the developmental duration of the four host species from the juvenile mite stage to the second nymph stage.The prophase of maturity is 11.91 d（Crabapples）,11.45 d（Apple）,10.98 d（Pear）,and 10.93 d（Peach）in descending order.Among them,the prematurity of mites that feed on pear and peach trees is significantly shorter than Feeding on the other two hosts,the population reproduces faster.When feeding on peach trees,the average number of eggs per female of P.citri was the most,54.05 seeds/female,followed by pear trees（49.62seeds/female）,which was significantly higher than that of apples and crabapples.When P.citri feeds on pears,apples,peaches and crabapples,the average number of eggs per female（F）is 49.62,35.83,54.05,and 37.08 eggs/female;the net proliferation rate（R₀）is 36.72,respectively.25.80,41.08 and 26.70;the intrinsic growth rate（r）is 0.1974 d^-1,0.1774 d^-1,0.2012 d^-1 and 0.1728 d^-1,the weekly growth rate（λ）is 1.2182 d^-1,1.1942 d^-1,1.2229 d^-1 and1.1886 d^-1;the average generation period（T）is 18.26 d,18.32 d,18.46 d and 19.01 d,respectively.Among them,the intrinsic growth rate r is greater than 0,and the weekly growth rateλis greater than 1,and the population can grow geometrically normally.The above studies indicate that the P.citri has spread to open orchards in northern my country.Although the current field investigations have only found that it has caused serious damage to pear trees,it also has a strong ability to multiply on apples,peach trees,crabapple and other plants.There are serious threats to fruit trees and landscaping plants.This research has sounded the alarm for plant protection workers and fruit farmers in northern fruit trees:the distribution range of P.citri has moved north,and the composition of pest mites in northern orchards may have changed.