Integrated management of false codling moth, Thaumatotibia leucotreta, on stone fruit and table grapes

Steyn, Vernon Murray (2019-03)

Thesis (PhDConsEcol)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: Integrated pest management (IPM) strives to control insect pests with a multifaceted approach that mirrors that of the ecology and endeavours to restore balance to the agricultural environment. To ensure the success of an IPM programme it is vital to understand the biology and the life cycle of the target insect. False codling moth (FCM), Thaumatotibia leucotreta is a tortricid moth with an extensive host range of more than 70 plants and is a key pest on citrus, stone fruit and table grapes. Insecticides are still relied upon for the control of FCM however, due to stricter regulations and their cascading environmental effects, there is a drive to reduce the chemical load in our agricultural environments. This encourages the need for a more sustainable approach such as IPM, which targets every stage in the life cycle of FCM. In this study, entomopathogenic nematodes (EPNs) and entomopathogenic fungi (EPF) were isolated from agricultural soils. The susceptibility of eggs and pupae to EPNs was investigated, and both entomopathogen types were screened against larvae. The EPNs proved to be the more potent pathogen and the larval stage was the least resilient against the pathogen. The EPN species that showed the most promise in laboratory trials were used as an in vitro cultured product and were tested in the field against FCM. The EPNs caused mortality of FCM larvae within 48 h and remained effective four weeks after application. Mating disruption is a nonchemical control technique that interferes with the mate-finding ability of insects in order to reduce mating events and is therefore an ideal candidate for the control of FCM. However, the effect of mating disruption has not been quantified against FCM in stone fruit and table grapes. Using multiple mark-release-recapture experiments, this is the first study to reliably quantify mating disruption in stone fruit and table grapes. Mating disruption proved to be a highly successful technique causing up to 99% disorientation of male FCM, but how the method alters FCM’s mate-finding ability was unclear. To determine FCM’s behavioural response to the addition of the female pheromone, quantitative tools and dosage-response profiles were used. The study proved that at low dosages the success of mating disruption is dependent on FCM density, however at high dosages there is a shift to non-competitive disruption causing mating disruption to remain effective even at high pest densities with few pheromone point sources. The integration of the techniques investigated here will ensure the effective control of FCM at each stage of the life cycle, ensuring low population growth that may lead to the successful suppression of this problematic pest.

AFRIKAANSE OPSOMMING: Geïntegreerde plaagbestuur (GPB) streef daarna om insekplae te beheer met 'n veelvlakkige benadering wat die ekologie weerspieël en poog om biologiese balans in die landbouomgewing te herstel. Om die sukses van 'n IPM-program te verseker, is dit noodsaaklik om die biologie en die lewensiklus van die teikeninsek te verstaan. Valskodlingmot (VKM), Thaumatotibia leucotreta is 'n tortricid mot met 'n wye gasheerreeks van meer as 70 plante en is 'n belangrike plaag op sitrus, steenvrugte en tafeldruiwe. Insekdoders word steeds aangewend vir die beheer van VKM maar, as gevolg van strenger regulasies en hul negatiewe omgewings-effekte, is daar 'n beweging om die hoeveelheid chemiese produkte in ons landbou-omgewings te probeer verminder. Dit moedig die behoefte aan om 'n meer volhoubare benadering soos GPB te volg, wat elke stadium van VKM se lewensiklus teiken. In hierdie studie, is entomopatogeniese nematodes (EPNs) en entomopatogeniese swamme (EPF) vanaf landbougrond geïsoleer. Die vatbaarheid van eiers en papies vir EPNs is ondersoek, terwyl beide entomopatogene teen laatinstar larwes getoets was. Die EPNs was die sterker patogeen en die larwale stadium was die mees vatbaar. Die EPN-spesies wat die mees belowende resultate in laboratoriumproewe getoon het, is as 'n in vitro gekweekte produk gebruik en in die veld teen VKM getoets. Die EPNs het die mortaliteit van VKM-larwes binne 48 uur veroorsaak en was na vier weke na toediening nogsteeds effektief. Paringsontwrigting is 'n nie-chemiese beheerstegniek wat inmeng met die vermoë van insekte om mekaar opstespoor, wat paringsgeleenthede verminder en is dus 'n ideale kandidaat vir die beheer van VKM. Paringsontwrigting teen VKM is egter nog nie in steenvrugte en tafeldruiwe gekwantifiseer nie. Met behulp van meervoudige-merkhervang eksperimente, is hierdie die eerste studie om paringsontwrigting betroubaar te kwantifiseer in steenvrugte en tafeldruiwe. Paringsontwrigting het tot 99% van VKM se paringsgeleenthede verminder en is dus 'n hoogs suksesvolle tegniek, maar hoe die beheer VKM se vermoë om mekaar op te spoor verander het, was steeds onduidelik. Om VKM se gedragsreaksie na die toevoeging van die vroulike feromoon te bepaal, is kwantitatiewe modele en doses-reaksieprofiele gebruik. Die studie het bewys dat by lae dosisse is die sukses van paringsontwrigting afhanklik van die grootte van die VKM bevolking, maar by hoë dosisse is daar 'n verskuiwing na nie-kompeterende ontwrigting wat veroorsaak dat paringsontwrigting doeltreffend bly, selfs met groot VKM bevolkings en min feromoonbronne. Die integrasie van die tegnieke wat hier ondersoek word sal verseker dat VKM effektief beheer word tydens elke stadium van die lewensiklus. Dit sal lae bevolkingsgroei verseker wat kan lei tot die suksesvolle onderdrukking van hierdie problematiese plaag.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/105706
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