The objective of this study was to determine differences in small mammal assemblage structure and population dynamics among four oak dominated sites at four different stages of gypsy moth disturbance: a high tree mortality site, a disturbance in process site, a disturbance recovery site, and an undisturbed reference site. More specifically, the study was designed to identify changes in habitat structure that would influence small mammal microdistributions and determine the quality of habitat created by gypsy moth herbivory using demographic structure of <i>Peromyscus</i> populations as an indicator of habitat quality. <i>Peromyscus leucopus</i>, Peromyscus maniculatus, the Soricids, and <i>Clethrionomys gapperi</i> had greater abundances at the disturbed sites relative to the reference site. Gypsy moth disturbance increased the abundance of small mammals and the number of coexisting species within a given area, which was attributed to several changes in habitat structure. The disturbed sites were characterized as having more fallen logs and standing dead snags, greater shrub and herbaceous cover, and higher invertebrate abundances relative to the reference site. These changes in habitat structure provided small mammals with increased cover from avian predators, more food resources, and potential nesting cavities. <i>P. leucopus</i> populations at the high mortality site exhibited greater demographic stability than the reference Site populations. This was marked by higher proportions of females, smaller density fluctuations, more fall recruitment of young, higher residency, and lower proportions of males. Strong evidence for density-dependent population regulation was observed for <i>P. leucopus</i> populations at the high mortality site and the <i>P. maniculatus</i> population at the recovery site. At high densities these populations exhibited extensive intraspecific microhabitat segregation. Female adults segregated from juveniles and male adults into more optimal microhabitats. Male adult microhabitat use significantly differed from male juvenile microhabitat use. The exclusion of young mice from optimal microhabitats by adults may be a mechanism by which adults limit over-exploitation of resources by subordinate members of the population at high densities. The results of this study suggest that gypsy moth disturbance of areas dominated by chestnut oaks at least temporarily improves habitat quality for small mammals. / Master of Science

Respondents of the 1986 Broccoli Growers Survey grew an average of 6.2 acres of broccoli in Fall 1986; popular varieties were Green Valiant (87.5% of respondents), Packman and Emperor (62.5%). Less than 5% of tobacco land was converted to broccoli production by 62.5% of the growers. Before heading, 2.4 insecticidal sprays were applied for worms at $20.51/acre. During heading, 2.4 insecticidal sprays were applied for worms at $19.40/acre. Under normal growing conditions, a nine-day mean of 8.4 and a 15-day mean of 12.1 cabbage looper larvae/plant did not significantly reduce yield in the Spring and Fall respectively. However, means of 7.4 and 11.1 cabbage looper larvae/plant reduced yield (head weight) under drought conditions. Harvest date was not affected by the above cabbage looper levels. In Fall 1986, a reduction in yield occurred when plants had 50% or more defoliation and harvest date was significantly delayed at 100% defoliation. In the drought stressed Spring 1987 planting, a stimulation in yield occurred at 25% defoliation and 75% defoliation was needed to significantly reduce yield, but there was no difference in harvest date. The imported cabbageworm was the most abundant pest of broccoli in Montgomery Co., VA. Based on counts of all immature stages of the insects for three seasons, Packman and Southern Comet varieties were less preferred compared to Green Defender. Laboratory studies indicated that imported cabbageworm larvae developed faster to the fifth instar on Packman broccoli than those reared on Green Defender, Southern Comet or Emperor. Difference in amount consumed between varieties was not detected. Pupae reared on Southern Comet weighed significantly more than those reared on Packman. / M.S.

During June 1990 - November 1993 I measured the responses of black bears (Ursus americanus) in Shenandoah National Park (SNP), Virginia to gypsy moth (Lymantria dispar) induced oak (Quercus spp.) mortality. Oak species composed >50% of the forest canopy of SNP, and oak mortality rates ranged from 1- ≥48%. I compared black bear population dynamics, food habits, movements and habitat use to preinfestation data collected in SNP from 1982 - 1985. Scat analysis indicated that the current diet of SNP’s black bear population includes proportionally more soft mast in the fall and more soft mast and ants (Formicidae spp., P<0.0001) in the summer than did the preinfestation diet. Fewer acorns (Quercus spp. mast, P=0.03) and squawroot (Conopholis americana, P=0.01) were consumed in the fall and summer respectively. No decline in the physical condition of adult females (P=0.91), subadult males (P=0.34) or subadult females (P=0.94) was evident. Adult male physical condition declined (P=0.03) for unknown reasons. The mean age of neither female (P=0.99) nor male bears (P=0.54) was different from preinfestation data. Mean litter size - 2.25 cubs - did not differ (P=0.49) froma preinfestation mean of 2.0 cubs. Survival of radio-collared female bears was 100%, indicating that the female survival rate has not declined from a high preinfestation survival rate. Minimum cub survival rate to 1 year was 64.7%. Fall and annual home ranges of female bears were smaller (P=0.001 and P=0.002, respectively) than during preinfestation years. Use of forest cover types differed from availability during the summer (P<0.01), early fall (P<0.0001) and late fall (P<0.001) and when compared to preinfestation data. Use of stands with different levels of oak mortality was not different from availability during the summer (P=0.1) but was different during the early fall (P<0.005) and late fall (P<0.001). / Master of Science

The Nantucket pine tip moth, Rhyacionis frustrana (Comstock) Is a common pest of young pines. In the eastern United States all species of yellow pines are attacked to some degree except longleaf pine, Pinus palustrla Mill. (Yates 1960). Chemical control of the tip moth has been demonstrated to be effective, but It generally has been considered to be too expensive since the evidence was only Inconclusive as to any permanent additional height growth of pines resulting from complete control. There has been considerable speculation about silvicultural control and a number of methods have been suggested by various workers. Many of these methods, however, have not been backed by quantitative data. Some of the suggested silvicultural controls are mixing susceptible species with resistant species, starting. trees under an overstory, using close spacing, and starting trees In brush. To date, there have been no detailed investigations of silvicultural control for the tip moth. This study was designed to determine if stands of loblolly pine, Pinus taeda L., growing under various conditions show any differences in rate of attack by the tip moth that might, In the future, be a basis for silvicultural or integrated control. / Master of Science

The susceptibility of a population of diamondback moth, Plutella xvlostella L (Lepidoptera: Plutellidae), collected from Montgomery County, Virginia, and its ability to develop resistance to Bacillus thuringiensis was evaluated. The field population of diamondback moths was found to be susceptible to B. thuringiensis. Selection pressure at 153 I.U. of B. thuringiensis endotoxin per ml for nine generations did not cause any significant difference in mean mortality of third instar diamondback moths although there was a trend towards lower mortality, there was significant negative linear correlation between generation and mean mortality of diamondback moth larvae (P = 0.003, r²= 0.73). LC₅₀ increased from 264 I.U. of B. thuringiensis endotoxin per ml in generation I to 514 LU/ml in generation IX. The interrelationship of B. thuringiensis to diamondback moth and its primary parasitoid, Diadegma insulare Cress (Hymenoptera. Ichneumonidae), was studied by determining: the differential response of third instar diamondback moth, parasitized and unparasitized, to B. thuringiensis, and the ability of D. insulare to discriminate between B. thuringiensis-treated and untreated hosts. There was no significant difference (P > 0.05) between mean mortality of parasitized and unparasitized larvae at each of the three concentrations consisting of 154, 334, and 2237 I.U. of B. thuringiensis endotoxin per ml. The regressions of the response of parasitized and unparasitized larvae, however, were highly significant (P = 0.0001). The LC₅₀s of parasitized versus unparasitized larvae were 373 and 176 I.U./ml B. thuringiensis endotoxin, respectively. Female D. insulare did not discriminate between B. thuringiensis-treated and untreated hosts. The percentage of D. insulare females emerging from B. thuringiensis-treated larvae (41.4%) was not significantly different from that of untreated larvae (32.0 %). Mean mortality of third instar diamondback moth subjected to B. thuringiensis endotoxin at 153, 334, and 2237 I.U./ml were not significantly different at temperatures of 15 and 20 °C, but were significantly lower than that at 30 °C. The effects of B. thuringiensis endotoxin residues on leaves under room conditions [27 ± 1 °C, RH 27 ± 72%, and 8:16 (L:D)] were not significantly different at 2 and 192 hours after treatment. / Master of Science

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.

The diamondback moth, Plutella xylostella (Linnaeus 1758.) (Lepidoptera: Plutellidae), is a major insect pest of Brassica crops in many parts of the world leading to economic losses amounting to an estimated US$ 4-5 billion. Although parasitoids (biological control agents) play a major role in suppressing the pest populations during November – May in South Africa, the pest reaches outbreak status during September and October due to low impact of parasitoids, which has necessitated regular application of insecticides. However, insecticide applications have often resulted in the pest developing resistance, and when coupled with the negative effects of several insecticides on parasitoids, integration of the two pest control strategies for effective management of P. xylostella population density has been difficult to achieve. One approach that has received little attention is integration of host plant resistance (bottom-up effect) and biological control (top-down effect) for effective management of P. xylostella. However, the interaction between host plants, the insect pest, and parasitoids is not simple and straight forward, as strong negative impact of host plants on fitness of the insect pest can be cascaded up the food chain and have a negative impact on a given parasitoid, which in turn may reduce the desired complementary effect between the two pest control strategies. To identify optimal interactions between cabbage (Brassica oleracea L. var. capitata, Brassicaceae), P. xylostella and its larval parasitoid Cotesia vestalis (Haliday 1834) (Hymenoptera: Braconidae), this study investigated (i) the effects of seven cabbage cultivars (Empowa, Hollywood F1, Megaton, Leano, Menzania, Beverley Hills and Karabo) on fitness parameters (survival, developmental time, pupal weights, longevity without food and oviposition rates) of P. xylostella; (ii) the influence of the same host plant cultivars on fitness parameters (developmental time, pupal weights, longevity xi without food, fecundity, emergence rate and sex ratio) of C. vestalis. Furthermore, net reproductive rates and the intrinsic rates of natural increase were calculated for C. vestalis that emerged from hosts fed on each of the cultivars. All experiments were conducted in climate-controlled laboratory rooms maintained at 22 ± 1 ºC (mean ± S.D.), 60 ± 5 % RH and 16L: 8D photoperiod. Under the no choice test, overall survival of P. xylostella immature stages was highest on Karabo (67.26%) and lowest on Megaton (44.92%). The larval and pupal developmental period, and generation time was prolonged on Empowa (18.48 days), Karabo (14.64 days) and Beverly Hills (17.48 days), while developmental period on Hollywood F1 (13.79 days) was shortest. Male and female P. xylostella pupal weights were lighter from larvae that fed on Megaton (4.13 and 4.65 mg), Menzania (4.53 and 4.91 mg), and Hollywood F1 (4.11 and 5.08 mg), whereas pupal weights from Karabo (6.0 and 6.82 mg) were the heaviest. Unfed female moths originally reared on Beverley Hills had the highest longevity (5.05 days), whereas those reared on Leano (3.54 days) and Megaton (3.89 days) had the shortest life span. Under the choice-test, P. xylostella moth laid significantly more eggs on Empowa (48.8%) and Hollywood F1 (45.6%) and least on Menzania (11.8%) and Leano (10.6%). Megaton was more resistant to P. xylostella due to lower survival rates of immature stages, lower pupal weights and moth longevity. The generation time of C. vestalis was shortest on Karabo (10.10 days) and Leano (10.38 days), and longest on Megaton (12.57 days) and Empowa (12.80 days). The highest pupal weight of C. vestalis was obtained from parasitoids reared from P. xylostella fed Menzania (5.4 mg), Megaton (5.25 mg) and Beverly Hills (4.85 mg) and the lightest on Karabo (3.8 mg). Parasitoids reared on larvae that fed on Hollywood F1 lived the longest (2.28 days) followed by Menzania (1.94 days) and Beverly Hills (1.8 days), whereas those whose hosts fed on Leano had shortest life span (0.83 days). Despite the parasitoids from Megaton hosts being heavier, their fecundity and number of female progeny per female (16.87 and 3.60, respectively) were lowest. Cotesia vestalis fecundity and daughters produced per female were highest on hosts fed on Menzania (38.00 and 9.13, respectively) and Beverly Hills (32.87 and 9.07, respectively). As a consequence, the net reproductive rate (R0) and intrinsic rate of increase (r) were higher on Menzania (7.87 and 0.58, respectively) and Beverly Hills (8.29 and 0.62, respectively). As survival and overall fitness of P. xylostella was lower on Megaton, this cultivar can play a major role in restricting population growth of this pest and thus generational number of eggs deposited on it during September and October. However, this strong bottom-up effect of Megaton on P. xylostella was cascaded up the food chain, as overall fitness of C. vestalis was lower on hosts developing on it. In contrast, the overall fitness of C. vestalis was higher on hosts that developed on Menzania and Beverly Hills. As these cultivars showed potential to sustain population density of C. vestalis at higher levels, it is also assumed that the period required for the parasitoid to reach the critical density to suppress the host population at a lower average density will be reached quicker than on other cultivars. Thus, their cultivation may improve biological control of P. xylostella during November–May in South Africa / Agriculture, Animal Health and Human Ecology / M. Sc. (Agriculture)

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.

Doctor of Philosophy / Department of Entomology / Raymond A. Cloyd / James R. Nechols / Raymond A. Cloyd / James R. Nechols / Greenhouse studies were conducted to examine direct effects of light intensity and nitrogen source on primary and secondary metabolism of pac choi (Brassica rapa L. var. chinensis cv. ‘Mei Qing Choi’) and indirect effects on diamondback moth (Plutella xylostella L.)(DBM). In the first study, plants were exposed to high and low light intensities during different times of the year, resulting in a range of light intensities. From four experiments, plants exhibited higher phenolic content, greater shoot biomass, and higher C:N ratios under high light intensity, whereas plants under low light intensity contained higher protein. Ferulic acid increased under high light intensity, and this increase was negatively correlated with male DBM body weights. However, DBM developed faster on plants in the August experiment (high light), compared to the July experiment (lower light). This implies that light intensity may not be affecting DBM through plant-mediated changes unless reduced male weights confer a reduction in larval consumption. In the nitrogen source study, application of an organic source of nitrogen (fish hydrolysate fertilizer) was compared to a conventional fertilizer to determine whether nitrogen source directly impacts pac choi chemistry and biomass, thus indirectly impacting DBM fitness. In two experiments, there was no significant effect of fertility treatment on pac choi nutrients or biomass, with the exception of percent leaf phosphorus, which was significantly higher in the conventional fertility treatment. For DBM, percent survival and cohort development were significantly reduced on pac choi receiving the organic fertilizer. Calcium and magnesium were significantly higher in pac choi infested with DBM larvae than plants without DBM. In addition, calcium was negatively correlated with female DBM body weights in one experiment for the organic treatment. Overall, this study demonstrated that pac choi plants that received the organic fertilizer were similar to pac choi plants that received a conventional fertilizer with the exception of phosphorus. Furthermore, female DBM body weights were negatively impacted by calcium in the organic treatment. As multiple fitness traits for DBM were negatively affected in the organic treatment, pac choi crops grown with fish hydrolysate fertilizer may experience less feeding from DBM.