Investigation On Natural Enemy Species In Nanning And Research On Predatory And Parasitic Characteristics Of Major Natural Enemies Of Diaphorina Citri

Diaphorina citri（Liviidae:Hemiptera）is an important insect-vector of citrus Huanglongbing.Chemical insecticides are mainly used to control D.citri in the field.Using natural enemies to control D.citri has the advantages of environment friendly and sustainable.Investigation on the natural enemies of D.citri and research on their predatory and parasitic characteristics could provide basis data and theoretical basis for biological control of D.citri.Adults,eggs and nymphs of D.citri began to appear in March and only adults could be seen in December on Murraya exotica hedgerow where chemical insecticides were not sprayed.The highest peak period of D.citri populations（971.5 head/m²）were in September from August to December,2020,the highest peak period of D.citri populations（1071.8head/m²）were in May from March to July,2021.D.citri had obvious generation overlap in the field.Temperature was the main meteorological factor affecting the population number of D.citri.When the monthly mean temperature was higher than 22.3℃（from March to October）,it was beneficial to the growth and reproduction of D.citri.Total 15 species of natural enemies were found on Murraya exotica hedgerow and Citrus reticulate cv.Shatangju trees where chemical insecticides were not sprayed,in which,9 species natural enemies belong to Insecta,including Menochilus sexmaculata,Propylea japonica,Lemnia biplagiata,Oenopia chinensis,Harmonia axyridis,Chrysoperla sinica,Tamarixia radiate,Diaphorencyrtus aligarhensis and Marietta picta;6 species natural enemies belong to Arachnida,including Phintella vittate,Thomisus labefactus,Rhene rubigera,Phintella versicolor,Oxyopes sertatus and Anystis baccarnm.The dominant predatory natural enemy is M.sexmaculata and the dominant parasitic natural enemy is T.radiate.P.vittate,T.labefactus,R.rubigera,P.versicolor and M.picta as natural enemies of D.citri were firstly reported in China.The ultrastructure of M.sexmaculata antennae were observed.Sensilla chaetica with a pore at the base,sensilla trichoidea with a verrucous surface,dumbbell sensilla and sausage sensilla were firstly observed on antennae of M.sexmaculata.The feeding preferences of M.sexmaculata to D.citri were observed.Larvae and adults of M.sexmaculata prefered to feed on D.citri nymph,especially the healthy and full 5^th nymph.The predatory behavior of M.sexmaculata consisted of 3 stages:searching,controlling and feeding.The predation response of M.sexmaculata to the 5^th nymph of D.citri was in accordance with the Holling II equation,with instantaneous attack rates of 0.995 and 1.726,treatment times of 0.003 d and 0.008 d,pest control efficacy of 315.8 and 207.9,maximum daily predation rates of120.48 head/d and 317.46 head/d,for the 4^th larvae and adults of M.sexmaculata,respectively.The scent of citrus leaves,adult D.citri and citrus leaves with adult D.citri were all significantly attractive to M.sexmaculata,in which,adult D.citri alone had the strongest attractive to M.sexmaculata.T.Radiate larvae inside the body of D.citri nymph and emergence hole on the surface of D.citri nymph were observed in May,but parasitized nymph of D.citri were not observed in December on Murraya exotica hedgerow where chemical insecticides were not sprayed.The peak period of parasitism rate of T.Radiate was in September（21.2%）from August to December,2020,and it was in June（14.2%）from March to July,2021.The parasitism rate range of T.Radiate was 4.2%to33.7%in the citrus planting areas in Xiangzhou county of Laibin city and Lipu city of Guilin city.Psyllaphycus diaphorinae,a hyperparasitoids of D.citri was found during investigation,its host wasp is T.radiate.