Pre-release evaluation of the flea beetle Heikertingerella sp. (Coleoptera: Galerucinae: Alticini), a potential biological control agent for the invasive weed Tecoma stans L. (Bignoniaceae) in South Africa = Ukuhlolwa okungaphambi kokukhishwa kwezeze eliyibhungane i-Heikertingerella sp. (Coleoptera: Galerucinae: Alticini), i-ejenti yokulawula yebhayoloji engabakhona yokhula oluhlasela i-Tecoma stans L. (Bignoniaceae) eNingizimu Afrikha.

Abstract

The root-feeding beetle Heikertingerella sp. (Coleoptera: Chrysomelidae) was introduced into quarantine in South Africa for evaluation as a biological control agent of the invasive tree Tecoma stans L. (Bignoniaceae). Larval feeding damages the roots, potentially reducing the weed’s growth and reproduction. Pre-release studies in quarantine included several aspects. Studies on the beetle’s biology and host specificity were conducted to confirm its safety for release in South Africa. The impact of varying beetle densities on plant fitness was assessed to determine its likely impact in the field. The effect of local climate on the beetle’s potential to establish throughout the weed’s range in South Africa was predicted using climate-modelling software. The interaction between Heikertingerella sp. and a leaf-feeding agent already established in South Africa was investigated. Finally, the effect of host-plant age and nutrient enhancement on mass-rearing activities was studied, to optimize beetle numbers for releases. The beetle proved host specific resulting in the granting of permission for its release in South Africa. There were significant reductions in plant growth and biomass accumulation in the beetle-exposed plants, relative to the controls, indicating that Heikertingerella sp. is sufficiently damaging. Climate matching revealed that Heikertingerella sp. is likely to perform best at coastal sites in South Africa, with the colder, more inland, areas within the weed’s range proving less suitable. The beetle proved compatible with a defoliating agent established in South Africa, with evidence of positive interactions that are likely to enhance their combined impact on the weed. Trials involving plants of varying age and nutritional enhancement revealed that 3-year-old plants, which were supplemented by either medium or high levels of fertilizer, were best suited for F1 progeny production and therefore for the mass-rearing of Heikertingerella sp. for releases. The results of this study should also benefit other countries in Africa and elsewhere in the world, where the plant is invasive.

Iqoqa.

Ibhungane elincelisa izimpande i-Heikertingerella sp. (Coleoptera: Chrysomelidae) yethulwa endaweni eyodwa eNingizimu Afrikha ukuze ihlolwe njengomenzeli wokulawula isayensi yezinto eziphilayo yesihlahla esihlaselayo i-Tecoma stans L. (Bignoniaceae). Ukondliwa kwezibungu kulimaza izimpande, okungase kunciphise ukukhula nokuzala kokhula. Izifundo ezikhishwe ngaphambilini zokuvalelwa zibandakanya izici ezimbalwa. Kwenziwa ucwaningo ngesayensi yezinto eziphilayo yebhungane kanye nemininingwane yalo ukuze kuqinisekiswe ukuphepha kwalo ukuze likhishwe eNingizimu Afrikha. Umthelela wokuminyana kwamabhungane okuhlukahluka kokuqina kwezitshalo wahlolwa ukuze kutholwe umthelela ongase ube nawo ensimini. Umthelela wesimo sezulu sendawo emandleni ebhungane okwakha ukhula lonke eNingizimu Afrikha wabikezelwa kusetshenziswa isoftware yokufanisa isimo sezulu. Ukusebenzisana phakathi kwe-Heikertingerella sp. kanye nomenzeli wokuphakela amaqabunga kade kusunguliwe eNingizimu Afrikha kwaphenywa. Ekugcineni, umthelela weminyaka yezitshalo ezibamba iqhaza kanye nokuthuthukiswa komsoco emisebenzini yokukhulisa ubuningi kwacwaningwa, ukuze kwandiswe izinombolo zebhungane ukuze zikhishwe. Ibhungane labonakala likhethekile okwaholela ekunikezweni kwemvume yokukhululwa kwalo eNingizimu Afrikha. Kube nokuncipha okukhulu ekukhuleni kwezitshalo kanye nokunqwabelana kwe-biomass ezitshalweni ezivezwe yibhungane, uma kuqhathaniswa nezilawuli, okubonisa ukuthi i-Heikertingerella sp. ilimaza ngokwanele. Ukuqhathanisa isimo sezulu kwembula ukuthi i-Heikertingerella sp. kungenzeka ukuthi isebenze kahle kakhulu ezindaweni ezisogwini eNingizimu Afrikha, lapho kubanda, phakathi nezwe, izindawo ezingaphakathi kokhula zikhombisa ukungafaneleki. Ibhungane labonakala lihambisana nomenzeli wokubola owasungulwa eNingizimu Afrikha, nobufakazi bokusebenzelana okuhle okungenzeka kuthuthukise umthelela wabo ohlangene nokhula. Izivivinyo ezibandakanya izitshalo ezineminyaka ehlukene kanye nokuthuthukiswa komsoco kwembula ukuthi izitshalo ezineminyaka emi-3 ubudala, ezengezwe ngezinga eliphakathi noma eliphezulu likamanyolo, zazifaneleka kakhulu ekukhiqizeni inzalo ye-F1 futhi ngenxa yalokho ekukhulisweni kwenqwaba ye-Heikertingerella sp. ukukhishwa. Imiphumela yalolu cwaningo kufanele izuzise namanye amazwe ase-Afrika nakwezinye izindawo emhlabeni, lapho lesi sitshalo sihlasela khona.