Biology And Host Specificity Of Gallerucida Bifasciata (Coleoptera: Chrysomelidae) And Apoderus Bicallosicollis (Coleoptera: Attelabidae)

Classical biological control through introduction of host-specific natural enemies from native regions has been regarded as one of the promising approaches against invasive plants worldwide for more than 100 years.Host specificity of foreign natural enemies are becoming more and more critical in classical biological control programs, as concerns about potential risk from introduced biocontrol agents have been increasing recently.Understanding the insect's biology and host specificity is the first step in determining the potential for introduction of an insect to control invasive plants.Japanese knotweed,Fallopia japonica(Houttuyn) Ronse Decraene(Polygonaceae) is an invasive weed in the United States and Europe and Chinese tallow,Triadica sebifera(L.) Small(Euphorbiaceae),is also an invasive plant in the southeastern United States of America,they all native to China.This study researched the biology and host specificity of Gallerucida bifasciata(Coleoptera:Chrysomelidae) and Apoderus bicallosicollis(Coleoptera:Attelabidae) which is a potential biological control agent for Japanese knotweed and Chinese tallow respectively.The main results are as follow:1.Gallerucida bifasciata is a univoltine leaf beetle and its immatures could successfully develop at 15-30℃,but over 30℃its adults could diapause.In Wuhan, its adults aestivate from July to September and overwinter from October to March next year.2.Gallerucida bifasciata larvae were able to complete development on seven of 87 plant species in larval development tests,while adults fed and oviposited on 10 plants in no-choice tests.Multiple choice tests showed adults strongly preferred Fallopia japonica,Persicaria perfoliata(L.) H.Gross and Polygonum multiflorum Thunb over all other plants.Open field tests and field surveys further revealed that these three species were in its ecological host range.3.The results of this study suggest that G.bifasciata is a potential promising agent for control of Japanese knotweed in the United States and Europe,although additional host specificity tests and risk assessment should be completed.4.Apoderus bicallosicollis occurs over a wide,native,geographic range and its immatures successfully develop at 15-35℃,indicating its physiological potential to establish and persist throughout the range of climatic conditions where the target plant grows in the US.Adults feed on leaves and make feeding holes.Before oviposition, the female adult rolls a leaf to make sealed leaf rolls called nidi,and then lays 1-2 eggs inside.Eggs,larvae and pupae develop within nidi and larvae survive only when they develop inside the tallow nidi.This requirement makes the weevil highly host-specific to T.sebifera.5.Laboratory no-choice tests of 54 species from 8 families indicated that adults fed on 3 plant species,T.sebifera,Sapium chihsinianum S.K.Lee,Phyllanthus urinaria L.,but only oviposited on T.sebifera.In multiple choice tests adults only laid eggs on T.sebifera and when feeding strongly preferred T.sebifera over Phyllanthus urinaria.In the field,no damage or eggs were found on 32 plant species of 17 families growing near T.sebifera.6.Given that T.sebifera is the only species in the genus Triadica in the US,the results of this study suggested that A.bicallosicollis is a potential biological control agent of T.sebifera and should be considered to be imported into quarantine in the US for further tests on native North American species.