Initial investigation of Trichogrammatoidea lutea (Hymenoptera: Trichogrammatidae) as biological control agent of codling moth, Cydia pomonella (Lepidoptera: Tortricidae), in apple and pear orchards, under sterile insect technique (SIT)
Year: 2008
Type: dissertation
Abstract: Codling moth (CM), Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae), is the major pest of apples and pears in the South Western Cape, South Africa.Apart from conventional insecticide sprays, area-wide biologically intensive control methods, such as Sterile Insect Technique (SIT) and pheromone mediated mating disruption (MD) are currently in use on two farms in the Elgin valley.The indigenous parasitoid Trichogrammatoidea lutea Girault (Hymentoptera: Trichogrammatidae) attacks eggs of false codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), as well as CM and has been found to have considerable parasitism potential on both.Elevated host egg numbers, as achieved by SIT are thought to support establishment of populations of these natural enemies in the orchards.For rapid and secure Trichogrammatoidea species identification, the ITS2 sequences of Trichogrammatoidea lutea and T. cryptophlebiae Nagaraja (an indigenous FCM parasitoid on citrus) were determined and species specific primers were developed.Lifetable studies of T. lutea indicated an optimal temperature for reproduction at around 20 °C.Food was provided by the application of honey-solution soaked cotton wool, behind fine netting.The effect of food provision by this method was found to be dependent on temperature.The acceptance of CM eggs from sterilized vs. fertile parents and of radiation-sterilized eggs vs. fertile ones was assessed in choice trials.While no difference was observed between radiated and fertile eggs, sterile eggs from irradiated parents were significantly less attractive than eggs from fertile parents.In several field studies the dispersal capacity and population sustainability of released T. lutea were investigated.Trials took place in apple and pear orchards in the Elgin valley that formed part of an area-wide sterile CM SIT program.Most of the wasp releases were carried out within blocks of up to 1 ha.A square grid of up to 36 monitoring trees per block allowed spatial distribution analysis.Following single central point releases, parasitism of sentinel eggs was recorded until the end of all experiments, the longest of which lasted 37 weeks.T. lutea females were found to disperse up to 73 m, within one week.Studies concerning toxicity of four commonly used insecticides and one fungicide to immature and adult T. lutea indicated no to low susceptibility of wasps at egg-to first-instar-stage within host eggs.Contact toxicity of the tested materials to adults differed significantly, depending on the compound.All five pesticides caused significantly higher mortality among adults relative to the control.iv The overall aim of above studies was to determine the potential of T. lutea for broad-scale releases against CM, within a broader integrated pest management program in apple and pear orchards in the Western Cape.Opsomming Kodlingmot (KM), Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae), is die belangrikste plaag in die appel-en peerbedryf in die Suidwes-Kaap.Buiten besproeiing met normale insekdoders, word biologies intensiewe beheermetodes, soos die vrylating van steriele insekte en paringsontwrigting, tans wyd gebruik op twee plase in die Elgin-vallei.Die inheemse parasitoïed Trichogrammatoidea lutea Girault (Hymentoptera: Trichogrammatidae) val die eiertjies van die valskodlingmot (VKM), Cryptophlebia leucotreta (Meyrick) (Lepidoptera: Tortricidae), sowel as dié van die KM aan, en daar is gevind dat dit 'n redelike mate van parasietbesmetting by albei veroorsaak.Daar word gemeen dat 'n verhoogde getal gasheereiers, wat deur steriele-insektegniek (SIT) bereik kan word, die vestiging van populasies van hierdie natuurlike vyand in die boorde sal bevorder.Om Trichogrammatoidea-spesies vinnig en akkuraat te kon identifiseer, is die ITS2-stringe van Trichogrammatoidea lutea en T. cryptophlebiae Nagaraja ('n inheemse parasitoïed op VKM in sitrusboorde) bepaal en spesiespesifieke grondvorme ontwikkel.Studies oor die lewensiklus van T. lutea het daarop gedui dat 'n optimaal gunstige temperatuur vir reproduksie ongeveer 20 °C is.Kos is voorsien deur watte met 'n heuningoplossing te deurweek en dit agter 'n fyn net beskikbaar te stel.Daar is gevind dat die uitwerking van hierdie metode van temperatuur afhanklik is.Die aanvaarding van gasheereiers van gesteriliseerde volwasse motte teenoor dié van vrugbare volwasse motte, en van eiers wat deur bestraling steriel gemaak is teenoor vrugbare eiers, is deur steekproewe bepaal.Terwyl geen verskil waargeneem is tussen bestraalde en vrugbare eiers nie, was die steriele eiers van bestraalde volwasse motte aansienlik minder aantreklik as dié van vrugbare volwasse motte.In verskeie veldnavorsingsprojekte is die verspreidingskapasiteit en bevolkingshandhawing van losgelate T. lutea ondersoek.Proefnemings is gedoen in appel-en peerboorde in die Elgin-vallei, wat deel gevorm het van 'n wydverspreide SIT program van KM.Die meeste motte is losgelaat in gebiede van tot 1 ha groot.Die vierkantige koördinaatnet met tot 36 bome per blok wat gekontroleer is, het dit moontlik gemaak om 'n ruimtelike verspreidingsanalise te doen.Nadat loslating vanaf 'n enkele v sentrale punt geskied het, is die parasitisme op waargeneemde eiers opgeteken tot aan die einde van alle eksperimente, waarvan die langste 37 weke geduur het.Daar is gevind dat T. Lutea-wyfies in staat is om tot 73 m te versprei, binne een week.Studies oor die giftigheid van vier algemeen gebruikte insekdoders en een swamdoder op onvolwasse en volwasse T. lutea het aangetoon dat papies in die gasheereiers lae of geen vatbaarheid toon vanaf die eierfase tot met die eerste instar nie.Kontakgiftigheid van die getoetste middels vir volwassenes het aansienlik verskil en was van die samestelling afhanklik.Al vyf insekdoders het aansienlik meer sterftes onder die volwassenes meegebring as die waterkontroleproef.Die oorkoepelende doelwit van bogenoemde studies is om die potensiaal van 'n grootskaalse loslating van T. lutea teen kodlingmot binne 'n breër en geïntegreerde beheerprogram te ondersoek, in appel en peer boorde in die WesKaap.
Author: Nadine Wahner
Language: English
Subfield: Insect Science
Domain: Life Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W2149050815