Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The codling moth, Cydia pomonella (Lepidoptera: Tortricidae), is the key pest of apples and pears worldwide. The withdrawal of certain fundamental chemicals from codling moth management spray programmes, due to concerns about human, environmental and ecosystem health, has resulted in the search for softer, more environmentally friendly, and safer control measures. Entomopathogenic nematodes (EPNs), naturally occur in the soil, and actively search for hosts. The interest in using EPNs from the families Heterorhabditidae and Steinernematidae as a control measure was sparked in 1953, when an EPN was discovered in an insect. The aim is to incorporate EPNs in an integrated pest management (IPM) programme, to ensure minimal residue and eventually residue-free pome fruit production in South Africa. In order to ensure EPN success, both the environmental and technical factors influencing their efficacy, were investigated in this study. The biocontrol potential of three imported EPN isolates, being Steinernema feltiae and two isolates of Heterorhabditis bacteriophora (Hb1, Hb2), as well as a local isolate, Steinernema yirgalemense, were evaluated for the control of the codling moth under local conditions. All concentrations of S. yirgalemense, applied by immersion in a suspension of nematodes, gave > 98% control. The two formulated isolates of H. bacteriophora, Hb1-f and Hb2-f, gave < 30% control. When using the same nematode isolates, produced in vivo, S. yirgalemense still resulted in a higher codling moth control of > 90%, compared to 54% and 31% control of the H. bacteriophora Hb1 and Hb2 isolates, respectively. In follow up field trials, S. feltiae resulted in ≥ 80% control, and was thus more effective than both S. yirgalemense and the H. bacteriophora (Hb1) isolates, with 66% and 24%, and 24% and 9% control, for two separate trials, respectively. To validate the data obtained from the field trials, subsequent laboratory bioassays were conducted evaluating temperature regimes, following the same cycle as under natural conditions, with a constant humidity of 100%. Steinernema feltiae proved to be most effective, causing > 90% mortality, followed by S. yirgalemense, with 78% mortality. The two H. bacteriophora isolates (Hb1, Hb2) under the above-mentioned laboratory conditions, resulted in 73% and 59% control, respectively. Humidity thus seems to be the most important factor affecting EPN efficacy during above-ground applications. Steinernema feltiae proved to be a better candidate than S. yirgalemense for the control of the codling moth. The efficacy of different EPN isolates in controlling diapausing codling moth larvae at different temperatures was also evaluated, under local conditions, using spray application. Steinernema feltiae and two isolates of H. bacteriophora Hb1 and Hb2, including two local isolates, S. yirgalemense and Steinernema jeffreyense, were evaluated. The use of S. jeffreyense resulted in the most effective control, with 67% mortality, followed by H. bacteriophora (Hb1) with 42%, and then by S. yirgalemense with 41%. Laboratory bioassays simulating field conditions revealed that S. feltiae was most virulent to codling moth larvae, with 67% mortality by infection, followed by S. yirgalemense with 58%, the H. bacteriophora strain Hb1 with 48%, and the Hb2 strain with 24%. A comparison of the infection and penetration rate of two isolates of H. bacteriophora (Hb1, Hb2), S. feltiae and S. yirgalemense, which was carried out in multiwell plates at 14°C and 25°C, respectively, confirms the dramatic effect of temperature on EPN efficacy. At 14°C, all treatments with EPN species resulted in slower codling moth mortality than they did at 25°C, as after 48 h, < 15% mortality was recorded for all species, whereas at the warmer temperature, > 98% mortality was recorded for all species. After the exposure of washed, cool-treated larvae to 25°C for 24 h, the application of both S. feltiae and S. yirgalemense resulted in 100% mortality, whereas the application of the two H. bacteriophora isolates, Hb1 and Hb2, resulted in 68% and 54% control, respectively, over the same time period. At 14°C, S. feltiae had the highest average penetration rate of 20 IJs/insect, followed by S. yirgalemense with 14 IJs/insect, whereas S. yirgalemense had the highest penetration rate at 25°C, with 39 IJs/insect, followed by S. feltiae, with 9 IJs/insect. The two H. bacteriophora isolates had higher average penetration rates at the higher temperature. This study has highlighted the biocontrol potential of S. jeffreyense, as well as showing that S. feltiae is a cold-active nematode, whereas the other three EPN isolates prefer warmer temperatures. Stacked wooden fruit bins are regarded as preferred overwintering sites for codling moth diapausing larvae. Control strategies against the codling moth in South Africa have been hampered by the reinfestation of orchards by nearby stacked infested fruit bins or by the movement of bins between orchards. Worldwide, wooden fruit bins are systematically being replaced with plastic bins, which, in South Africa, will only be phased out over a few years. The objective of this study was to evaluate the potential of H. bacteriophora, S. feltiae, and S. yirgalemense, to disinfest miniature wooden fruit bins under controlled conditions in the laboratory. After dipping minibins in a suspension of 25 IJs/ml of all three EPN species, under optimum conditions of temperature and humidity, the highest percentage of control was obtained using S. feltiae (75%) followed by S. yirgalemense (57%), and then by H. bacteriophora (Hb1) (27%). The addition of adjuvants significantly increased (p < 0.001) S. feltiae infectivity to > 95%, whereas it did not result in a significant increase in H. bacteriophora or S. yirgalemense infectivity. The results indicated that H. bacteriophora would not be a suitable candidate to use for the control of the codling moth larvae in wooden fruit bins. The current preferred candidate for control would be S. feltiae, whose efficacy could be increased by means of the addition of an adjuvant. During winter, when the whole codling moth population are larvae and in diapause, no control measures are applied in orchards. This study has shown that EPNs can be sprayed in orchards to lower the codling moth cohort emerging after winter, as well as be included in an IPM programme. EPNs can act as a second line of defence, through supplementary control, and ensure effective control of the codling moth larvae which survived chemical spray applications, to safeguard against resistant codling moth populations in the next season. / AFRIKAANSE OPSOMMING: Kodlingmot, Cydia pomonella (Lepidoptera: Tortricidae), is ‘n belangrike plaag van appels en pere wêreldwyd. Die onttrekking van sekere fundamentele chemikalieë vanuit die kodlingmot beheerprogram weens die kommer oor menslike, omgewings en ekosisteemgesondheid, het gelei tot die soektog na sagter, meer omgewingsvriendelike en veiliger beheermaatreëls. Entomopatogeniese nematodes (EPNs) kom natuurlik in die grond voor en soek aktief na gashere. Die belangstelling in die gebruik van EPNs van die families Heterorhabditidae en Steinernematidae as 'n beheermaatreël is te danke aan die ontdekking van 'n EPN in ‘n insek in 1953. Die doel is om EPNs in 'n geïntegreerde plaagbeheerprogram (GPB) te inkorporeer om sodoende minimale residue te verseker en uiteindelik residu vrye produksie van kernvrugte in Suid-Afrika. Ten einde die sukses van EPNs te verseker, is beide die omgewings- en tegniese faktore wat hul doeltreffendheid beïnvloed in die studie ondersoek. Die biologiese beheer potensiaal van drie ingevoerde EPN isolate, Steinernema feltiae en twee Heterorhabditis bacteriophora (Hb1, Hb2) isolate, sowel as 'n plaaslike isolaat, Steinernema yirgalemense, is vir die beheer van kodlingmot onder plaaslike toestande geëvalueer. Alle konsentrasies van S. yirgalemense, wat deur indompeling in ‘n suspensie van nematodes toegedien is, het > 98% beheer tot gevolg gehad. Die twee geformuleerde isolate van H. bacteriophora, Hb1-f en Hb2-f, het < 30% beheer gegee. Met die gebruik van dieselfde nematode isolate, wat in vivo geproduseer is, het S. yirgalemense nog steeds 'n hoër kodlingmot beheer van > 90% opgelewer, in vergelyking met die 54% en 31% beheer van die H. bacteriophora Hb1 en Hb2 isolate, onderskeidelik. Steinernema feltiae het in opvolg veldproewe ≥ 80% beheer tot gevolg gehad en was dus meer effektief as beide S. yirgalemense en die H. bacteriophora (Hb1) isolate, met 66% en 24% en 24% en 9% beheer onderskeidelik in twee afsonderlike veldproewe. Om die resultate van die veldproewe te bevestig, is daaropvolgende laboratorium biotoetse uitgevoer en temperatuur regimes is geëvalueer deur die selfde siklus as onder natuurlike toestande te volg, met 'n konstante humiditeit van 100%. Die studie het bewys dat S. feltiae die mees doeltreffende isolate was met > 90% mortaliteit, S. yirgalemense het gevolg met 78% mortaliteit. Die twee H. bacteriophora isolate (Hb1, Hb2) het onderskeidelik onder bogenoemde laboratorium toestande 73% en 59% beheer tot gevolg gehad. Humiditeit blyk dus die belangrikste faktor te wees wat EPN se doeltreffendheid tydens bogrondse toediening affekteer. Die studie het bewys dat S. feltiae 'n beter kandidaat as S. yirgalemense vir die beheer van kodlingmot is. Die doeltreffendheid van verskillende EPN isolate vir die beheer van diapause kodlingmot larwes sowel as EPN se aktiwiteit by verskillende temperature is ook onder plaaslike toestande, deur bogrondse bespuitings, geëvalueer. Steinernema feltiae en twee isolate van H. bacteriophora (Hb1, Hb2), S. yirgalemense en ‘n ander plaaslike isolaat, Steinernema jeffreyense, is geëvalueer. Die gebruik van S. jeffreyense, het tot die mees effektiewe beheer gelei, met 67% mortaliteit, gevolg deur H. bacteriophora (Hb1) met 42%, en dan S. yirgalemense met 41%. Laboratorium biotoetse wat veldtoestande simuleer, het bewys dat S. feltiae die mees doeltreffend teen kodlingmot larwes is, met 67% mortaliteit tydens infeksie, gevolg deur S. yirgalemense met 58%, die H. bacteriophora Hb1 isolaat met 48%, en die Hb2 isolaat met 24%. 'n Vergelyking van die infeksie- en penetrasie tempo van twee isolate van H. bacteriophora (Hb1, Hb2), S. feltiae en S. yirgalemense wat in 12-put plate teen 14°C en 25°C uitgevoer is, het die dramatiese effek van temperatuur op EPN doeltreffendheid bevestig. By 14°C het alle EPN spesies behandelings stadiger kodlingmot mortaliteit as by 25°C na 48h tot gevolg gehad. ‘n Mortaliteit van < 15% is vir alle spesies aangeteken terwyl by die warmer temperature is > 98% mortaliteit vir alle spesies aangeteken. Na die blootstelling van afgespoelde, koel behandelde larwes aan 25°C vir 24 uur, het die toediening van beide S. feltiae en S. yirgalemense, 100% mortaliteit van larwes tot gevolg gehad terwyl die toediening van die twee H. bacteriophora isolate, Hb1 en Hb2, onderskeidelik 68% en 54% beheer tot gevolg gehad, oor dieselfde tydperk. By 14°C, het S. feltiae die hoogste gemiddelde penetrasie tempo van 20 ILs/ larwe, gevolg deur S. yirgalemense met 14 ILs/ larwe tot gevolg gehad, terwyl S. yirgalemense die hoogste penetrasie tempo getoon het by 25°C met 39 ILs/ insek, gevolg deur S. feltiae met 9 ILs/ insek. Die twee H. bacteriophora isolate (Hb1 en Hb2) het ook hoër gemiddelde penetrasie tempo by die hoër temperatuur getoon. Hierdie studie het die biobeheer potensiaal van S. jeffreyense beklemtoon, asook weereens bevestig dat S. feltiae ‘n koue-aktiewe nematode is, terwyl die ander drie EPN isolate warmer temperature verkies. Hout vrugtekratstapels, word beskou as ‘n ideale oorwintering skuiling vir kodlingmot diapause larwes. In Suid-Afrika word beheerstrategieë teen kodlingmot in die wiele gery deur die herbesmetting van boorde deur nabygeleë besmette hout vrugtekratte of deur die beweging van kratte tussen boorde. Hout vrugtekratte word wêreldwyd stelselmatig vervang met plastiek kratte. Dit sal egter eers oor ‘n aantal jare in Suid-Afrika uitgefaseer word. Die doel van hierdie studie was om die potensiaal van H. bacteriophora, S. feltiae, en S. yirgalemense te evalueer deur miniatuur hout vrugtekratte onder gekontroleerde toestande in die laboratorium te disinfekteer. Na die onderdompeling van die mini vrugtekratte in 'n nematode suspensie van 25 ILs/ml van al drie EPN spesies, onder optimale toestande van temperatuur en humiditeit, is die hoogste persentasie van beheer met die gebruik van S. feltiae (74,85% ± 3.64%) verkry. Die byvoeging van toevoegings middels het S. feltiae se vermoë om te infekteer betekenisvol (p <0,001) tot > 95% verhoog, maar dit het nie tot 'n betekenisvolle toename in die infektiwiteit van H. bacteriophora of S. yirgalemense gelei nie. Die resultate dui daarop dat H. bacteriophora nie 'n geskikte kandidaat is om te gebruik vir die beheer van kodlingmot larwes in besmette hout kratte nie. Die voorkeurkandidaat tans vir beheer is S. feltiae, waarvan die doeltreffendheid verhoog kan word deur middel van die byvoeging van 'n bymiddel. Gedurende die winter wanneer die hele kodlingmot populasie as larwes in diapause is, word geen beheer in boorde toegepas nie. Hierdie studie het getoon dat EPNs in boorde gespuit kan word om sodoende die opkomende kodlingmot populasie na die winter te verlaag en kan ook ingesluit word in 'n GPB program. Die EPNs kan as 'n tweede verdedigingslinie optree en doeltreffende beheer van kodlingmot larwes verseker wat chemiese bespuitings oorleef het, en sodoende beskerming teen weerstandige kodlingmot populasies in die volgende seisoen bied.

The biology and behavior of the codling moth, Cydia pomonella (L.), was studied to determine factors responsible for differences in susceptibility to moth damage among apple and pear cultivars. In release experiments, codling moth adults were intercepted in significantly greater numbers in host (apple, pear) than in non-host (maple) trees, suggesting a directed response rather than random movement to host trees. There was no correlation between adult preference for certain hosts and the susceptibility of the hosts to codling moth attack. Adults were guided by cues from the tree canopy, foliage and fruit. Cues from host fruit were less important at the beginning of the season. Similar adult behavior patterns were observed in different coding moth strains. However, moths reared on apples were guided more by olfactory cues from fruit than sterilized moths reared on artificial diet. The percentage of moths mating under caged conditions was higher in apple and pear than in maple trees. In host plants, stimuli from fruit were not essential for mating. The egg distribution in the field varied through the season depending on the host cultivar. However, mean distance of eggs to fruit, as well as larval travel speed, was not different among host cultivars. Selection of an oviposition site by the adult female was affected by several factors, including visual, chemical, and tactile stimuli of host fruit, as well as anatomical (pubescence) and chemical (oviposition stimulants) properties of leaves. There were no differences in natural mortality and developmental rates of the egg stage on host cultivars. However, there were significant differences in first instar larval mortality among hosts over most of the season. Mortality was much higher on 'Anjou' than on 'Bartlett' and 'Red Delicious', except at the end of the season. Differential first instar mortality was due to the different rate of success in entering the fruit. The ability to penetrate fruit was correlated with infestation levels observed in the field and related both to neonate behavior and anatomical characteristics of host fruits. Larval food source did not affect larval and pupal development rates, adult fecundity, or egg viability. / Graduation date: 2001

Graduation date: 1995

The codling moth, Cydia pomonella (Tortricidae) is a significant pest in apple orchards. In the 1990ies, a control programme using the Sterile Insect Technique (SIT) has been established, based on bisexual releases of sterile insects into wild populations of this pest. Male-only releases are not possible due to the lack of an efficient system to produce male-only progeny. Recently, a new approach has been proposed for the development of genetic sexing strains in Lepidoptera. It is based on insertion of a dominant conditional lethal mutation of the Notch gene, derived from the N60g11 allele of Drosophila, into the female W chromosome by means of transgenesis. This study deals with isolation, characterization, and chromosomal localization of a codling moth orthologue of the Drosophila Notch gene with the aim to prepare a mutant sequence of the orthologue to be used in plasmid constructs for germline transformation of this pest.

The codling moth, Cydia pomonella (Lepidoptera; Tortricoidea) is a major pest of pome fruitand walnut orchards in the world. Due to the intensive chemical control C. pomonella has developed a high resistance to various insecticides. One of the mechanisms of the resistance is acetylcholinesterase insensitivity to carbamates and organophosphates. The insensitivity is based on mutations in one of two genes for acetylcholinesterase. This study deals with testing a hypothesis suggesting that one gene coding for acetylcholinesterase in the codling moth was translocated to the Z sex chromosome. The hypothesis has been latersupported by sex-linked inheritance of insecticide resistance in a related species, Grapholita molesta, and also by a large size of sex hromosomes in the codling moth.

Tortricid moths (Lepidoptera) are known for their outstanding olfaction capabilities that allow them to detect, process, and respond to chemical information emitted by host or non-host plants. Such an ability to filter out odors from the complex mixture to locate their host has allowed researchers and integrated pest management (IPM) practitioners to develop and implement semiochemically-based pest control strategies. The major goal of this study was to evaluate, under field conditions, the response of male and female oriental fruit moth (OFM), codling moth (CM), redbanded leafroller (RBLR) and three lined leafroller (TLLR) to experimental kairomone lures in commercial apple orchards in Massachusetts. My results indicate that (1) addition of benzaldehyde to Megalure® or to TRE2266 significantly increased captures of OFM males but not of CM males, (2) benzaldehyde was a strong male attractant-it was as attractive as Megalure® to OFM males, and (3) TRE2266 attracted significantly more RBLR than any other lure and by adding benzaldehyde it became attractive to TLLR. These findings highlight the opportunity to work with benzaldehyde to develop more efficient semiochemical-based monitoring and control systems for tortricid moths.

Cydia pomonella (Linnaeus) (Family: Tortricidae), the codling moth, is considered one of the most significant pests of apples and pears worldwide, causing up to 80% crop loss in orchards if no control measures are applied. Cydia pomonella is oligophagous feeding on a number of alternate hosts including quince, walnuts, apricots, peaches, plums and nectarines. Historically the control of this pest has been achieved with the use of various chemical control strategies which have maintained pest levels below the economic threshold at a relatively low cost to the grower. However, there are serious concerns surrounding the use of chemical insecticides including the development of resistance in insect populations, the banning of various insecticides, regulations for lowering of the maximum residue level and employee and consumer safety. For this reason, alternate measures of control are slowly being adopted by growers such as mating disruption, cultural methods and the use of baculovirus biopesticides as part of integrated pest management programmes. The reluctance of growers to accept baculovirus or other biological control products in the past has been due to questionable product quality and inconsistencies in their field performance. Moreover, the development and application of biological control products is more costly than the use of chemical alternatives. Baculoviruses are arthropod specific viruses that are highly virulent to a number of lepidopteran species. Due to the virulence and host specificity of baculoviruses, Cydia pomonella granulovirus has been extensively and successfully used as part of integrated pest management systems for the control of C. pomonella in Europe and around the world, including South Africa. Commercial formulations have been typically based on the Mexican strain of CpGV. However due to long-term multiple applications of CpGV and the reliance on CpGV in organic farming practices in Europe, resistance to the CpGV-M strain has developed in a number of field populations of C. pomonella. This study aimed to identify and characterize novel isolates of CpGV in South Africa and compare their virulence with the commercial standard CpGV-M. Secondly, since C. pomonella is difficult to culture on a large scale, an alternate method of CpGV production was investigated in order to determine if CpGV could be produced more efficiently and at a reduced cost without negatively impacting the quality of the product. Several isolates of CpGV were recovered either from field collected larvae or from a laboratory-reared C. pomonella colony. Characterisation of DNA profiles using a variety of restriction enzymes revealed that only a single isolate, CpGV-SA, was genetically different from the Mexican strain of the virus used in the commercially available CpGV based products in South Africa. In dose-response bioassays using CpGV-SA, LC₅₀ and LC₉₀ values for neonate C. pomonella larvae were 3.18 x 10³ OBs/ml and 7.33 x 10⁴ respectively. A comparison of these values with those of CpGV-M indicated no significant difference in the virulence of the two isolates under laboratory conditions. This is a first report of a genetically distinct CpGV isolate in South Africa. The biological activity and novelty of CpGV-SA makes this isolate a potentially important tool for CpGV resistance management in South Africa. In order to justify production of CpGV in an alternative host, studies on the comparative biological performance of C. pomonella and T. leucotreta based on oviposition, time to hatch, larval developmental times and rearing efficiency as well as production costs were performed. Thaumatotibia leucotreta was found to be more fecund and to have significantly shorter egg and larval developmental times. In addition, larval production per unit of artificial diet was significantly higher than for C. pomonella. This resulted in T. leucotreta being more cost effective to produce with implications for reduced insectary space, sanitation practices as well as the labour component of production. Virus yield data generated by inoculation both C. pomonella and T. leucotreta with nine concentrations of CpGV resulted in comparable virus yields, justifying the continuation of the research into production of CpGV in T. leucotreta. It was important to determine the LC and LT values required for mass production of CpGV in late instar T. leucotreta larvae. Dose- and time-response bioassays with CpGV-M were conducted on artificial diet to determine these values. Fourth instar LC₅₀ and LC₉₀ values were 5.96 x 10³ OBs/ml and 1.64 x 10⁵ OBs/ml respectively. LT50 and LT90 values were 81.10 hours and 88.58 hours respectively. Fifth instar LC₅₀ and LC₉₀ values were 6.88 x 10⁴ OBs/ml and 9.78 x 10⁶ OBs/ml respectively. LT₅₀ and LT₉₀ values were 111.56 hours and 137.57 hours respectively. Virus produced in fourth instar T. leucotreta larvae was bioassayed against C. pomonella neonate larvae and compared to CpGV-M to establish if production in the heterologous host negatively affected the virulence of the isolate. No significant difference in virulence was observed between virus produced in T. leucotreta and that produced in C. pomonella. The data generated in the bioassays was used in CpGV mass production trials to evaluate production. All production methods tested produced acceptable virus yields. To examine the quality of the virus product, genomic DNA was extracted from larval cadavers and subjected to REN analysis with HindIII. The resulting DNA profiles indicated that the virus product was contaminated with the homologous virus, CrleGV. Based on the above results, the use of T. leucotreta as an alternate host for the in vivo production of CpGV on a commercial basis is not at this stage viable and requires further investigation before this production methodology can be reliable used to produce CpGV. However, this study has shown that CpGV can be produced in a homologous host, T. leucotreta and significant strides have been made towards developing a set of quality control standards that are essential for further development of successful production methodology. Finally a novel isolate of CpGV has been identified with comparable virulence to the CpGV-M. This is an important finding as it has broad reaching implications for resistance management of CpGV products in South Africa.

Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae) is a devastating pest of pome fruit in temperate regions of the world. Control of this pest, previously involved the extensive use of broad-spectrum insecticides. However, concerns over human safety, environmental impact, widespread dispersal of resistant populations of codling moth and the sustainability of synthetic pesticides in agroecosystems, has encouraged the development and use of alternative environmentally-friendly pest management technologies including the use of entomopathogenic nematodes. These nematodes are lethal pathogens of insects and belong to the families Steinernematidae and Heterorhabditidae, and are ideal candidates for incorporation into the integrated pest management programme currently being developed for residue-free pome fruit production in South Africa. The biological and ecological factors pertaining to the successful use of these nematodes for the control of codling moth were investigated in this study. Their use for bin-disinfestations was evaluated, focusing on the optimum handling conditions to ensure the survival and subsequent efficacy of the nematodes. The study proved that the local isolate SF41 of Heterorhabditis zealandica Poinar 1990 could be used for successful bin-disinfestation. The use of the same nematode isolate was also investigated for the disinfestation of mulch layers of diapausing codling moth larvae. An insect containment device which allowed for direct trial efficacy evaluation was identified and ecological factors pertaining to the successful use of nematodes for mulch disinfestation were investigated. The biological control potential of local nematode isolates, which had previously never been tested against codling moth larvae, was investigated in the laboratory under conditions as can be expected during orchard applications. The efficacy of the selected isolates was confirmed in field experiments. Innovative insect containment methods for above-ground trial efficacy evaluation in the field were investigated. Desiccation proved to be the most limiting factor to the survival and subsequent efficacy of the nematodes during field applications in temperate regions. The effect of low moisture levels on H. zealandica’s efficacy to control diapausing codling moth larvae was subsequently investigated and a starch-based formulation was further tested to overcome the issue of desiccation. Conclusive results indicated that there were several biological and ecological factors influencing the survival of nematodes and illustrated how these factors could be manipulated to overcome these issues and thereby ensure the efficacy of treatments. This is the first report of its kind to comprehensively investigate the use of South African entomopathogenic nematodes for the control of diapausing codling moth larvae and all results emanating from the study can be integrated into a framework for the commercial use of these nematodes in this regard in future. / AFRIKAANSE OPSOMMING: Kodlingmot, Cydia pomonella (L.) is ‘n ernstige sleutelplaag in appel- en peerboorde in gematigde klimaats gebiede wêreldwyd. In die verlede is hoofsaaklik breëspektrum insektedoders gebruik vir die beheer van hierdie plaaginsek. Maar, kommer oor veiligheid vir die mens, impak op die omgewing, verspreiding van weerstandbiedende populasies van kodlingmot en beperkte volhoubaarheid van sintetiese plaagdoders het die ontwikkeling en gebruik van alternatiewe plaagbeheer tegnologieë, insluitend die gebruik van entomopatogeniese nematodes, genoodsaak. Entomopatogeniese nematodese horende tot die families Steinernematidae en Heterorhabditidae, is ideale kandidate vir insluiting in die geïntegreerde plaagbestuur programme wat huidiglik ontwikkel word vir gebruik in plaaslike boorde met die uiteindelike doel om residu-vrye vrugte te produseer. In hierdie studie word die biologiese en ekologiese faktore bestudeer wat die sukses van ‘n nematode-toediening gemik op kodlingmot beïnvloed. Hierdie studie het bewys dat die lokale SF41 isolaat van Heterorhabditis zealandica Poinar 1990 gebruik kan word om vrugtekratte te disinfesteer van kodlingmot. Die gebruik van dieselfde isolaat vir die disinfestasie van deklae is ook ondersoek. ‘n Metode van insek-inkamping is ook ontwikkel wat die evaluering van toedienings vergemaklik en meer effektief maak. Die omgewings-toestande wat ook bydrae tot die oorlewing en gevolglike sukses van ‘n toediening is ook ondersoek. Die biologiese beheer potensiaal van ‘n paar lokale isolate wat nog nooit voorheen teen kodlingmot getoets is nie, is ook bestudeer. Die isolate se effektiwiteit is ook bevestig in veldproewe en insek-bekampings metodes wat meer van toepassing is vir bogrondse plaaginsekte is ook geïdentifiseer. Resultate dui daarop dat vogverlies en gevolglike uitdroging van nematodes die grootste beperkende faktor is vir hierdie tipe toedienings in gematigde gebiede en ‘n stysel-gebaseerde formulasie is dus ondersoek om hierdie probleem te oorkom. Die uiteindelike gevolgtrekking van die studie was, dat alhoewel daar verskeie biologiese en ekologiese faktore is wat die oorlewing van nematodes beperk, daar tog verskeie maniere is om hierdie faktore te manipuleer en sodoende te oorkom, wat bydrae tot die uiteindelike sukses van ‘n toediening. Hierdie is die eerste studie wat werklik die praktiese gebruik van lokale entomopatogeniese nematodes vir die beheer van kodlingmot ondersoek en alle bevindinge kan geïntegreer word in toekomende riglyne vir die kommeriële gebruik van nematodes vir die beheer van kodlingmot.

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Cydia pomonella (codling moth), Thaumatotibia leucotreta (False codling moth), Thaumatotibia batrachopa (Macadamia nut borer), Grapholita molesta (Oriental fruit moth), Cryptophlebia peltastica (Litchi moth), Epichoristodes acerbella (Pear leafroller/Carnation worm) and Lozotaenia capensana (Apple leafroller) are the most economically important tortricids affecting various crops in South Africa. The correct identification of these species, especially of the larval stage, is of great importance in pest management. Using available literature, augmented by additional morphological studies, an interactive identification key (Lucid key) for larval and adult stages of the seven species was developed. The colour and markings of the head, characteristics of the prothoracic and anal shields, the position of the prespiracular setae (L-group) relative to the spiracle on the prothoracic segment, the position of the spiracle on the eighth abdominal segment and L-group on the ninth abdominal segment, as well as the presence or absence of the anal comb are key characteristics for larval identification. For adult identification, wing pattern and genitalia are the most important features. However, the use of genitalia for moth identification might be difficult for the lay user, as the dissection and mounting of these structures requires certain skills and specialized equipment. Thus, genitalia have not been included in the Lucid Key. Differences in the morphological characteristics of most pupae were so minute that this stage was also not included in the Lucid key. However, the pupae of E. acerbella and L. capensana are easily distinguished from those of the other species by the presence of acremaster. This study also included the first morphological description of the pupa of L. capensana, which can be distinguished from that of E. acerbella by various features of the cremaster, antennae, spiracle shape, number of setae on abdominal segments A5-7, the size of spines on A3-7, and the presence/absence of spines on A9. A previous study by Timm (2005) indicated that geographically isolated populations of T. leucotreta tend to be genetically distinct. This raised the question of whether speciation/subspeciation has occurred or is occurring. Male moth genitalia are thought to evolve rapidly and are often the only features that can reliably distinguish similar species. Hence, variation in the shape of the valvae of T. leucotreta was used to determine whether divergence has occurred between populations of T. leucotreta. Elliptical Fourier analysis was used to analyze the valvar variation in three different populations. Although some variation in valvar shape was detected among mean population values for certain traits, no clear pattern emerged. Principle component analysis also showed no distinct clustering of valvae shape among populations, providing no evidence for divergence in male genitalia and therefore no morphological evidence of incipient speciation. / AFRIKAANSE OPSOMMING: Cydia pomonella (Kodlingmot), Thaumatotibia leucotreta (Valskodlingmot), T. batrachopa (Makadamianeutboorder), Grapholita molesta (Oosterse vrugtemot), Cryptophlebia peltastica (Lietsjiemot), Epichoristodes acerbella (Peerbladroller/Angelierrusper) en Lozotaenia capensana (Appelbladroller) is die mees ekonomies belangrike tortrisiede van die vrugtebedryf in Suid-Afrika. Die juiste identifikasie van hierdie spesies, veral van hulle larwale stadium, is van groot belang by plaagbestuur. Deur gebruik te maak van beskikbare literatuur, aangevul deur bykomstige morfologiese studies, is ‗n interaktiewe uitkenningssleutel (―Lucid key‖) vir die larwale en volwasse stadia van die sewe spesies ontwikkel. Die kleur en tekening van die kop, kenmerke van die prothorakale en anale skild, die ligging van die prespirakulêre setae (L-groep) relatief tot die spiraculum op die prothorakale segment, die ligging van die spirakulum op die agste abdominale segment en L-groep op die negende abdominale segment, asook die aan- of afwesigheid van die anale kam is sleutel kenmerke vir larwale uitkenning. Vir die volwassenes is die vlerktekening en genitalia die mees belangrike kenmerke. Die gebruik van die genitalia vir motuitkenning kan egter vir die leek gebruiker moeilik wees omdat die disseksie en montering van hierdie strukture bepaalde vaardighede en gespesialiseerde toerusting vereis. Vir die rede is die genitalia nie in die Lucid-sleutel ingesluit nie. Verskille in die morfologiese kenmerke van meeste papies is klein en die stadium is gevolglik ook nie in die sleutel ingesluit nie. Die papies van E. acerbella en L. capensana kan egter maklik van die ander spesies onderskei word deur die aanwesigheid van ‗n cremaster. Hierdie studie sluit ook die eerste morfologiese beskrywing van die papie van L. capensana in, wat van dié van E. acerbella onderskei kan word deur gebruik te maak van kenmerke van die cremaster, antennae, spirakulêre vorm, aantal setae op abdominale segmente A5-7, die grootte van stekels op A3-7, en die aan- of afwesigheid van stekels op A9. ‗n Vroeëre studie (Timm 2005) het aangedui dat geografies geïsoleerde bevolkings van T. leucotreta neig om geneties verskillend te wees. Dit het die vraag laat ontstaan of spesiasie/subspesiasie moontlik plaasgevind het of steeds plaasvind. Manlike mot genitalië word geag om vinnig te ontwikkel en is dikwels die enigste kenmerke wat betroubaar tussen soortgelyke spesies kan onderskei. Dus is die variasie in die vorm van die valvae van T. leucotreta gebruik om te bepaal of divergensie wel tussen bevolkings van T. leucotreta plaasgevind het. Elliptiese Fourier ontleding is gebruik om die valvae se variasie by drie verskillende bevolkings te ontleed. Alhoewel enkele variasie in die vorm van die valvae bespeur is by die gemiddelde bevolkingswaardes vir bepaalde eienskappe, kon geen duidelike patroon bespeur word nie. Hoofkomponentontleding het ook geen duidelike groepering van valvae se vorm tussen bevolkings getoon nie, wat geen bewys lewer van divergensie in die manlike genitalia en dus geen morfologiese bewys van beginnende spesiasie.

Made available in DSpace on 2014-06-11T19:32:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-12-07Bitstream added on 2014-06-13T20:42:36Z : No. of bitstreams: 1 scomparin_alx_dr_jabo.pdf: 5977037 bytes, checksum: 8ab4f778519f1e5f248fa28ab2c97182 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A maioria dos organismos vivos são ectotérmicos, com exceção de pássaros e mamíferos. A temperatura corporal (Tc) de um ectotérmico é resultado da troca de calor entre o organismo e o meio ambiente e esta afeta a maioria das funções biológicas. Por exemplo, os insetos, para mudarem de estágio de desenvolvimento, requerem um mínimo de energia acumulada (calor). Para as pragas, a maioria dos modelos fenológicos é baseada na relação entre características do de desenvolvimento (ex., crescimento) e a temperatura do ar. Todavia, a utilização destes modelos ainda é limitada em razão da falta de exatidão na estimativa das temperaturas máximas e mínimas de desenvolvimento para a maioria das pragas. O objetivo deste trabalho foi avaliar a importância dos fatores: resistência a inseticidas e termoperíodo, assim como discutir os métodos de modelagem para o inseto endofítico Cydia pomonella. Para tal, se submeteu larvas e pupas de 4 linhagens diferentes desta espécie: sensível (Sv), resistente a diflubenzuron (Rdfb), resistente a deltametrina (Rdelta) e resistente ao granulovírus (Rgv), a 4 termoperíodos (15°C-20°C, 20°C-25°C, 25°C-30°C e 30°C- 35°C). Os parâmetros avaliados foram: taxa de crescimento, mortalidade, razão sexual e temperatura base, mínima e ótima de desenvolvimento do inseto. Com o auxílio dos valores obtidos nestes parâmetros, modelos lineares e curvilineares foram desenvolvidos, comparados entre si e com modelos obtidos por autores a temperaturas constantes. Os resultados mostraram que em condições de temperaturas variáveis a resistência implica em mudanças nos parâmetros biológicos (taxa de crescimento, mortalidade e razão sexual) e que o termoperíodo acelera o crescimento de larvas e pupas de carpocapsa. Com o auxílio dos modelos obtidos, foi realizada uma simulação do período de desenvolvimento de C. pomonella utilizando... / The majority living organisms are ectotherms except birds and mammals. The body temperature (Tb) of an ectotherm results from the energy balance between this the organisms and its environment. The Tb determines most of the biological functions. For instance, a minimum of heat accumulation by insects is needed to pass from a development stage to another during their life cycle. For insect pests, most of phenological models are based on life history trait (e.g., growth) and air temperature. Unfortunately, the use of phenological models is limited since there is a lack of accuracy estimatives in maximum and minimum temperatures. The aim this work was to study the importance of two factors ((i) the insecticide resistance, (ii) the thermoperiod) and the modelling methods to design a phenological model for the the endophyte insect Cydia pomonella. Four strains of C. pomonella: (i) Sv (susceptible strain), (ii) Rdfb (resistant to diflubenzuron), (iii) RD (resistant to deltamethrin), RGv (resistant to C. pomonella granulovirus) and 4 thermoperiods (15°C-20°C, 20°C-25°C, 25°C-30°C e 30°C-35°C) were used. Measured parameters were the development rate, the mortality, the sex ratio, the Toptm, Tmin and Tmax of the development rate. Based on the obtained values for each parameter, linear and curvilinear phenological models were made and compared between them and with those obtained at constant temperature by some authors. Thus, in fluctuating thermal conditions, it was shown that insecticide resistance involved aftereffects on life-history traits as the development rate, the mortality and sex ratio. Also, it was shown that the C. pomonella development rate at larval stage is higher in thermoperiodic conditions. With the models the development of C. pomonella was simulated using air and micro-habitat temperatures for two areas of apple orchards in Europe (e.g., Valais in Switzerland and la Drôme...(Complete abstract click electronic access below)