Thesis (MScAgric (Conservation Ecology and Entomology)--University of Stellenbosch, 2005. / The South African table grape industry exports approximately 60% of the table grapes produced. A major threat to the export of these grapes is the phytosanitary risk that insect pests pose. This study was conducted in the Hex River Valley, South Africa’s main table grape producing area. The aim of this study was to reduce the number of phytosanitary rejections from insects on table grapes from the Hex River Valley. Thus the main objectives of the study were to identify the most important phytosanitary pests in the Hex River Valley; the determination of their presence in the vineyards with possible means to control them; and to assess the possibility of using postharvest quarantine treatments in the Western Cape. Further aims were to determine the effect of different colour harvesting crates on the phytosanitary pests and whether the phytosanitary pests infested the grapes via packhouses. The most important phytosanitary pests of table grapes of the Hex River Valley are in order of importance: Phlyctinus callosus (Schonherr) (Coleoptera: Curculionidae), Epichoristodes acerbella Walker (Lepidoptera: Tortricidae), Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae), Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), Gonocephalum simplex Fabricius (Coleoptera: Tenebrionidae) and Dysdercus fasciatus Signoret (Hemiptera: Pyrrhocoridae). 12.71% of rejections were from species that were not identified, while a further 33% of the rejections were possibly identified incorrectly. Phytosanitary control of P. callosus appeared to be far more effective using Plantex® than pesticides. Weather conditions appeared to affect the abundance of P. callosus, especially warm weather, while bunches harboured less P. callosus later in the day. Control of E. acerbella with DiPel® (Bacillus thuringiensis var. kurstaki) appeared to at least reduce the population within the vineyards, and so its use is recommended. P. ficus is a non-actionable species for the USA market and is not listed as a phytosanitary pest for the Israeli market and so should not be causing any phytosanitary rejections. C. capitata appeared to be successfully controlled by the fruit fly sterile release program and the cold sterilisation it currently undergoes. G. simplex caused few rejections. It is still unclear where this pest infests the grapes, as it was found in both the field and in the packhouses. D. fasciatus occurrence on grapes was probably accidental. It was shown that picking during the early and late parts of the day, when this species was less active, reduced its occurrence in bunches. Gryllus bimaculatus (De Geer) (Orthoptera: Gryllidae), although not reported as a reason for rejections in table grapes for the past two years, was an actionable species that was present in large numbers in the Hex River Valley. There was a strong correlation between increasing quantities of pesticides and higher abundances of G. bimaculatus. It appeared to be an indicator of the overuse of pesticides. Results of this study showed that infestation by the phytosanitary pests came from neighbouring vineyards. The creation of barriers to prevent the movement of these pests between vineyards is suggested. Methyl bromide is the most commonly used postharvest quarantine treatment. Owing to the ozone-depleting properties of methyl bromide, it is scheduled to be outlawed in many countries from 2005. Alternative postharvest treatments are irradiation, extreme temperatures, forced air, vapour-heat treatments and the use of controlled atmospheres. Irradiation treatments appeared to control the pests at doses that do not damage the grapes. Controlled atmosphere treatments also have a high probability of success, although more research is required on this treatment. Low temperature treatments are relatively cheap as most exported fruit already undergoes cold storage, and appears to control species in the families Pseudococcidae and Tephritidae, although further research is required for the other pest. Colour or location of the harvesting crates in the vineyards appeared not to influence the number of phytosanitary pests collected, as they were not attracted to these crates.

An drei Standorten wurde die schädlingsregulierende Wirkung einer Raps-Rübsen-Mischsaat (Verhältnis 9:1) gegenüber einer Raps-Reinsaat bewertet. Des Weiteren wurden naturstoffliche und nach § 6a PflSchG selbst hergestellte Pflanzenschutzmittel als auch eine Käfersammelmaschine zur Regulierung der Stängelrüssler (Ceutorhynchus spp.) und des Rapsglanzkäfers (Meligethes aeneus F.) in Labor- und Freilandversuchen angewandt. In der Mischsaat war die Schaderregerabundanz gegenüber der Reinsaat zumeist erhöht. Diese führte zu einem teils signifikant stärkeren Schaderregerbefall der Rapspflanzen in der Mischsaat. Die Mischsaat erbrachte zudem einen teils signifikant geringeren Kornertrag. Natur-Pyrethrum und Spinosad führten im Labor zu deutlich erhöhten Mortalitäten bei den Stängelrüsslern. Im Freiland war kein Effekt erkennbar. Bei der Regulierung der Rapsglanzkäfer wies Spinosad in Feld- und Laborversuchen Wirkungsgrade bis zu 100 % auf. Gespritztes Gesteinsmehl und SiO2 zeigten einen nur geringen Effekt. Für die gleichmäßige Benetzung der Pflanzen mit diesen Präparaten kommt der Formulierung der Pflanzenschutzbrühe und der wiederholten Applikation eine hohe Bedeutung zu. Ökonomisch sind mehrfache Applikationen jedoch abzulehnen. Gestäubtes Gesteinsmehl und die Käfersammelmaschine sind aus Praktikabilitätsgründen nicht geeignet zur Regulierung der Rapsglanzkäfer. Ebenso wenig geeignet sind Quassin, Azadirachtin oder ein Bacillus thuringiensis-Präparat (B.t.t.). Mit Ausnahme einer Spinosad Applikation erzielte keine Pflanzenschutzmaßnahme einen wirtschaftlichen Mehrertrag. Stickstoffmangel und Unkrautkonkurrenz scheinen im ökologischen Rapsanbau häufig stärker auf die Limitierung der Kornerträge zu wirken als ein leichter bis mittlerer Schädlingsbefall. Je besser die Nährstoffversorgung und je geringer die Unkrautkonkurrenz, desto eher kann durch Pflanzenschutz ein wirtschaftlicher Mehrertrag realisiert werden. Die nötigen Pflanzenschutzkonzepte fehlen jedoch weiterhin. / On three sites the pest-regulating effect of a rape-turnip rape mixed cropping system (ratio 9:1) in comparison to rape in pure stand was assessed. Further, natural and self-produced natural insecticide solutions (§ 6a Plant Protection Act) and a beetle collecting machine to regulate the stem weevils (Ceutorhynchus spp.) and the pollen beetles (Meligethes aeneus F.) were applied in laboratory and field experiments. Compared to the fields in pure stand the mixed crop showed a significantly greater abundance of pests. This resulted in a sometimes significantly greater pest infestation of the rape plants in the mixed crop. Furthermore, the mixed crop often had a significantly lower grain yield. The use of natural pyrethrum and Spinosad resulted in significantly higher mortality rates of the stem weevils in laboratory tests. Under field conditions no effect could be detected. In the regulation of the pollen beetles, Spinosad demonstrated under field and laboratory conditions efficiencies of up to 100 %. Sprayed mineral powder or SiO2 had only a slight effect. For a uniform wetting of the plants with these compounds the formulation of the phytosanitary broth and its repeated application are important factors. From an economic perspective, however, repeated applications are inefficient. For reasons of practicality rock-dusted flour and the beetle-collecting machine are not suitable for pollen beetle regulation. Quassin is just as inappropriate as Azadirachtin, or Bacillus thuringiensis (B.t.t.) for the regulation of the pollen beetle. With the exception of one Spinosad application, no protection measure provided an economic surplus. Nitrogen deficiency and weeds seem to more frequently limit grain yield than slight to moderate pest infestation levels. The better the nutrient supply and the lower the weed competition, the more likely by crop protection can be realized an economic surplus. Adequate crop protection strategies, however, have not yet been developed.

A sample of 260 farm households that were randomly selected in Katumba ward, Rungwe district, Tanzania were studied for the effects of storage methods on the quality of maize grain and household food security using qualitative and quantitative methods. Maize storage problems, amounts of maize that farm households harvested and amounts of maize that farm households lost to pests per year, food security status and farm households’ perceptions concerning their food security status were investigated using face - to - face semi - structured and structured interviews. Common storage methods that farm households used to store maize and the dietary importance of maize were investigated through interviews, seasonal calendars and the matrix for scoring and ranking. The quality of maize was investigated through conducting mycological analysis and through investigating levels of insect infestation using the incubation method on maize samples collected from a sub-sample of 130 farm households at harvest and after five months of storage period. It was found that farm households in Katumba ward preferred maize meal rather than other types of food that provide bulk such as rice and green bananas/plantains. Maize contributed 66.8 % - 69.5 % of the total energy and 83 - 90 % of the total protein required per day, and farm households stored maize using roof and sack storage methods. It was also found that 34.5 % of 2323 tonnes of maize that were harvested per annum in Katumba ward were lost to pests during storage. Fusarium, Diplodia, Aspergillus and Penicilliums species were identified as the main fungal pathogens that attacked stored maize. Sitophilus zeamais, Sitotroga cerealella and rodents were also identified as the main maize storage pests. About 25 % of the maize samples that were collected at harvest and 93 % of the maize samples that were collected from the same farm households after five months of storage were infested by either Sitophilus zeamais or Sitotroga cerealella or both. Maize samples from the two storage systems had an average number of 80 insect pests per 120 maize kernels (or 51 g of maize), amounting to 1569 insects per kg. The high levels of insect infestation reduced the amount of maize that could have been available to the farm households and subjected stored maize to fungal infections and subsequent contaminations, thus, rendering the farm households vulnerable to food insecurity. Furthermore, it was also found that most of the infestation of maize by insect pests and moulds in Katumba ward occurred during storage, and that farm households were not well informed concerning maize storage and the negative effects that fungal activities in maize can have on the health of the consumers. An average of 87717 μg/kg fumonisins, 596 μg/kg aflatoxins, 745 μg/kg ochratoxins and 1803 μg/kg T-2 toxins were detected in the maize samples. Currently, there are no set standards for T-2 toxins, whereas the internationally accepted standards for aflatoxins, fumonisins and ochratoxins in cereals are 20 μg/kg, 4 mg/kg and 50 μg/kg, respectively. It was concluded that the levels of mycotoxins detected in maize from Katumba ward were far above the internationally accepted standards and that the farm households were at risk of ill health through consuming maize meals made from contaminated maize grain. The presence of high concentrations of mycotoxins, together with the high levels of insect infestation in the maize led to the conclusion that reduction of the nutrient content of the maize grain in Katumba ward was inevitable. Thus, the pests that infested maize stored using the roof and sack storage methods in this ward compromised not only the availability of food, but also the utilization of the nutrients in the maize and its safety, leading to the farm households’ food insecurity. It was further concluded that the quality of maize stored using roof and sack storage methods in Katumba ward was low and that the roof and sack storage methods were inadequate for protecting stored maize from pests. It was recommended that an efficient method for rapid drying of maize prior to storage be found, that the roof and sack storage methods be improved so that they can effectively protect stored maize from moisture content problems. It was also recommended that the farm households’ awareness concerning maize storage and food security be raised, and that the extension staff in Katumba ward should urge the Tanzanian government to implement an agricultural policy which promotes efficient maize storage and maize quality in order to improve the current status quo. Above all, since maize is the predominant staple, it was recommended that the maize breeding program in Tanzania should emphasize development of maize varieties that are resistant to ear rots, storage insects and to contamination by mycotoxins as part of a larger program to improve food security in this part of the country. Breeding programs that aim at enhancing the nutritional value of maize were also recommended. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Fourteen spore-forming bacterial strains were isolated and screened for entomopathogenic activity. Five displayed toxicity towards the common mealworm, Tenebrio molitor L., (Coleoptera: Tenebrionidae). The majority of the isolates were obtained from insect larvae and insect rich environments. The three bacterial species identified were Bacillus thuringiensis Berliner, Brevibacillus laterosporus Laubach and Bacillus cereus Frankland and Frankland. Bioassays were conducted using T. molitor larvae. The one isolate of B. cereus required the highest concentration of bacterial cells to achieve its LC50, whereas one of the isolates of B. laterosporus required the lowest cell concentration to achieve its LC50. Dose response curves were generated for the five best isolates, which showed that the isolate of B. laterosporus (NDR2) was substantially more toxic than the other isolates. / Thesis (Ph.D.) - University of KwaZulu-Natal, Pietermaritzburg, 2009.

Bean fly (Ophiomyia spp.) is a major pest of common bean (Phaseolus vulgaris L.) throughout eastern and southern Africa. In the semi-arid areas, apart from drought, the insect pest is reported to cause high crop losses up to 100%, particularly when drought occurs and under low soil fertility. Host-plant resistance is part of the integrated pest management strategies that have been widely employed against major insect pests of tropical legumes. However, information regarding its use in control of bean fly in common bean is limited. Therefore, the objectives of this study were to: (1) validate farmers’ perceptions of major constraints responsible for yield losses, particularly the major insect pests of beans; (2) asses the level of adoption of improved bean varieties and determine factors that influence farmers’ preferences of the varieties and criteria for selection; (3) identify sources of resistance to bean fly available in landraces; (4) determine the nature of gene action controlling bean fly resistance and seed yield in common bean; (5) describe a procedure for generating optimal bean fly populations for artificial cage screening for study of the mechanisms of resistance available in common bean against bean fly. Farmers considered drought and insect pest problems as main causes for low yields. The adoption rate for improved varieties was high but self-sufficiency in beans stood at 23% in the dry transitional (DT) agro-ecology and at 18% in the dry mid-altitude (DM) agroecology, respectively. Drought, earliness, yield stability, and insect pest resistance were the factors determining the choice of varieties by farmers. Bean fly (Ophiomyia spp.), African bollworm (Helicoverpa armigera) and bean aphid (Aphis fabae) were identified as key crop pests of beans limiting yield. The study to identify new sources of resistance included 64 genotypes consisting of landraces, bean fly resistant lines and local checks. The experiment was done under drought stressed (DS) and non-stressed (NS) environments and two bean fly treatments (insecticide sprayed and natural infestation) for three cropping seasons between 2008 and 2009. Genotypes differed in their reaction to natural bean fly attack under drought stressed (DS) and non-stressed environments (NS) over different cropping seasons. However, the effect of bean fly appeared to vary between the long rains (LR) and short rains (SR). It was observed that an increase in the number of pupae per stem resulted in a higher plant mortality. The range of seed yield was from 345 to1704 kg ha-1 under natural infestation and from 591 to 2659 kg ha-1 under insecticide protection. Seed yield loss ranged from 3 to 69 %. The resistance of most of the bean fly resistant lines seemed to be ineffective in presence of DS. To determine the nature of gene action controlling the inheritance of resistance to bean fly, four parents with known reaction to bean fly were crossed with four locally adapted genotypes in an 8 x 8 half-diallel mating design. Similarly, two resistant and two susceptible parents were selected and crossed to produce populations for generations means and variance components analysis. Results revealed that both general combining ability (GCA) and specific combining ability (SCA) mean squares were significant (p A 0.05) for all four traits studied, except SCA for stem damage during one cropping season. Among the parents, GBK 047858 was the best general combiner for all the traits studied across seasons except for stem damage during LR 2009. Genotypes GBK 047821 and Kat x 69 (a locally adapted variety) were generally good general combiners for resistance traits as well as seed yield. General predictability ratio values ranging from 0.63 to 0.90 were obtained for plant mortality, stem damage, pupae in stem and seed yield across cropping seasons. These results established the predominance of additive gene effects (fixable variation) over the non-additive effects in controlling the traits. Low to moderate narrow sense heritability values ranging from 0.22 to 0.45 were obtained for pupae in stem. Such heritability estimates indicate that although additive gene components were critical in the inheritance of resistance for the trait, non-additive gene action was also important in addition to the environmental effects. A major disadvantage in screening for resistance to bean fly in common bean by controlled means in net cages has been the lack of a method to use for raising adequate fly populations for screening. Due to this problem, a simple procedure for raising sufficient numbers of adult bean flies required for screening was described. Through this method, up to 62 % emergence of the adult flies was achieved. Moreover, the flies retained their ability to infest bean plants. To determine the presence of antibiosis and antixenosis mechanisms of resistance in common bean, five genotypes [CC 888 (G15430), GBK 047821, GBK 047858, Ikinimba and Macho (G22501)] and two local check varieties (Kat B1 and Kat B9) were screened under free-choice in outdoor net cages and no-choice conditions in net cages placed in a shadehouse. All the five resistant genotypes tested had relatively long internodes. It was established that long internode was a morphological trait associated with reduced pupation rate in bean stems, hence an antixenosis component of resistance. Both ovipositional non-preference and antibiosis mechanisms were found to exist in three genotypes namely CC 888 (G45430), GBK 047858 and Macho (G22501). These genotypes were resistant when they were subjected to bean fly under both free-choice and no-choice conditions. They had fewer feeding/oviposition punctures, low number of pupae in the stem, reduced damage to the stems and low percent plant mortality. The remaining genotypes, Ikinimba and GBK 047821 only expressed antixenosis. To maximize the effectiveness of host-plant resistance against bean fly, multiple insect resistances should be incorporated into a single bean genotype in order to ensure durability. However, this should be within the background of integrated pest management strategy. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

Typewritten copy / Includes bibliographical references / 1 v. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Waite Agricultural Research Institute, 1955

Thesis (M. En.)--Miami University, Institute of Environmental Sciences, 2004. / Title from first page of PDF document. Includes bibliographical references (p. 32-34).

Made available in DSpace on 2015-03-26T13:30:48Z (GMT). No. of bitstreams: 1 texto completo.pdf: 754859 bytes, checksum: b3501a3bf9aa715323fdceb139bc976d (MD5) Previous issue date: 2013-12-13 / Beans are the major source of protein in developing countries, and still the storage losses are estimated in 30% as a result of pests attack including Acanthoscelides obtectus (Say). Although chemical pesticides are effective to control these pests, their overuse can compromise the quality of food. Essential oils of vegetable origin are presented as an attractive alternative for the synthetic chemical insecticides to pest control, because they have little or no effect on grain quality, human health and environment. This study aimed evaluate the toxicity of the essential oils of Syzygium aromaticum (Myrtaceae) or clove and Cinnamomun zeylanicum (Laureaceae) known as cinnamon on A. obtectus in beans (Phaseolus vulgaris L.). We evaluated the instantaneous rate of increase (ri) of these insects exposed to time-lethal, developmental rate, repellency, persistence and loss of mass of the beans. The toxicity of the oils was evaluated by preliminary tests to estimate the lethal dose to 50 and 95% (DL50 and DL95) of adult insects. The experimental unit consisted of 0.8 L bottles containing 200 g of beans (Queen variety) treated with doses of 2,80; 5,54; 8,88; 14,22; 28,09 μL of clove oil, and 4,26; 6,93; 9,70; 13,60; 22,17 μL of cinnamon oil. Later were added 25 adult insects per vial (four replicates per dose), and insect mortality was assessed after 24 h. The instantaneous rate of increase (ri) of the oils of clove and cinnamon was determined using lethal doses (LD10, LD30, LD50, LD70 and LD90), obtained in the toxicity bioassay. After 45 days, the adult progeny was recorded; bottles with 200 g of beans and 25 adult insects, non-sexed 1-3 days old, and four replicates were used for LD. A similar procedure was done to assess the rate of development, with the difference that in this test the insects were removed from the flasks after 15 days they were introduced, and counting was performed every two days after the emergence of the first adult. The persistence was evaluated in beans treated with LD100 oils. The repellent activity of oils was tested with the LD10, LD50, LD90 doses for each oil. The results indicate that the toxicity LD50 and LD95 were 8.88 L and 38.94 L for clove essential oil, and 9.71 L and 27.97 L for cinnamon essential oil, respectively. Furthermore, with increased doses of essential oils and ri, development rate decreases significantly. Regarding the persistence of oil, was observed mortality reduction of A. obtectus with increasing time between the treatments of treated grains, keeping a higher mortality at 50% of the insects within 7 days after exposure. However, repellency of essential oil of cinnamon to this insect was observed only when using LD90; clove essential oil showed no repellency against A. obtectus at the tested doses. The loss of grain weight during 48 days was directly proportional to the number of emerged insects in each test. For beans treated with clove essential oil the average of mass loss was 6.6%, and 9.6% in the control, whereas for tests with essential oil of cinnamon the average of loss was 6.8% and 9.2% for the treatment and control, respectively. Thus, with the results obtained in this study, it can be concluded that the essential oils of clove and cinnamon have effect on mortality of A. obtectus by contact, as an alternative to the use of traditional insecticides. / O feijão representa uma das principais fontes de proteínas em países em desenvolvimento, ainda assim as perdas estimadas no armazenamento são de 30% em consequência do ataque de pragas, entre elas Acanthoscelides obtectus (Say). Embora os pesticidas químicos sejam eficazes para controlar essas pragas, seu uso excessivo pode comprometer a qualidade dos alimentos. Óleos essenciais de origem vegetal são apresentados como uma alternativa atrativa aos inseticidas químicos sintéticos para o controle de pragas, porque apresentam pouco ou nenhum efeito sobre a qualidade dos grãos, saúde humana e meio ambiente. Este trabalho teve como objetivo avaliar a toxicidade dos óleos essenciais de Syzygium aromaticum (Myrtaceae) ou cravo e Cinnamomum zeylanicum (Laureaceae) conhecida como canela sobre A. obtectus em grãos de feijão (Phaseolus vulgaris L.). Avaliou-se a taxa instantânea de crescimento populacional (ri) desses insetos expostos a tempos- letais, taxa de desenvolvimento, repelência, persistência e perda de massa do feijão. A toxicidade dos óleos foi avaliada através de testes preliminares para estimar a dose letal para 50 e 95% (DL50 e DL95) dos insetos adultos. As unidades experimentais foram constituídas por frascos de 0,8 L contendo 200 g de feijão (variedade rainha) tratados com doses de 2,80; 5,54; 8,88; 14,22; 28,09 μL de óleo de cravo, e 4,26; 6,93; 9,70; 13,60; 22,17 μL de óleo de canela. Posteriormente, foram acrescentados 25 insetos adultos em cada frasco (quatro repetições por dose), e a mortalidade dos insetos foi avaliada após 24 h. A taxa instantânea de crescimento (ri) dos insetos na presença dos óleos de cravo e canela foi determinada utilizando as doses letais (DL10, DL30, DL50, DL70 e DL90), obtidas no bioensaio de toxicidade. Foram utilizados frascos com 200 g de feijão e 25 insetos adultos, não-sexados com idade de 1-3 dias, e quatro repetições por DL; após 45 dias, a progênie adulta foi contabilizada. Procedimento similar foi feito para avaliar a taxa de desenvolvimento, com a diferença de, que neste teste, os insetos foram retirados dos frascos depois de 15 dias de terem sido introduzidos, e a contagem foi realizada a cada dois dias após a emergência do primeiro adulto. A persistência foi avaliada em grãos de feijão tratados com a DL100 dos óleos. A atividade repelente dos óleos foi testada com as doses DL10, DL50, DL90 para cada óleo. Os resultados de toxicidade indicaram que as DL50 e DL95 foram 8,88 L e 38,94 L para o óleo essencial de cravo, e 9,70 L e 27,97 L para o óleo essencial de canela, respectivamente. Além disso, com o aumento das doses dos óleos essenciais, a ri e a taxa de desenvolvimento decrescem significativamente. Com relação à persistência dos óleos, observou-se a redução na mortalidade de A. obtectus com o aumento do tempo entre o tratamento dos grãos tratados; mantendo uma mortalidade superior ao 50% dos insetos até 7 dias após a exposição. Entretanto, foi observada repelência do óleo essencial de canela para este inseto somente ao utilizar-se a DL90; o óleo essencial de cravo não apresentou repelência contra A. obtectus nas doses testadas. A perda de massa dos grãos no período de 48 dias foi diretamente proporcional ao número de insetos emergidos em cada teste. Para o feijão tratado com óleo essencial de cravo, a perda média da massa foi de 6,6%, e no controle de 9,6%; nos ensaios com óleo essencial de canela, a perda média foi de 6,8% e 9,2% para os tratamentos e controle, respetivamente. Assim, com os resultados obtidos nesta pesquisa, pode-se concluir que os óleos essenciais de cravo e de canela têm efeito por contato na mortalidade de A. obtectus, sendo uma alternativa ao uso de inseticidas tradicionais.

Lantana camara L. (Verbenaceae) remains a highly invasive and ecologically damaging weed in South Africa, despite some 50 years of biological control efforts. Lack of success has been ascribed to varietal differences, climate and predation of agents but these have not been tested. In this study, the effects of ant predation were tested on populations of three biological control agents for L. camara. Colonies of two species, Crematogaster sp. 1 and 2 were investigated. Crematogaster sp. 1 colonies were offered no choice between immature stages of the agents Hypena laceratalis Walker (Lepidoptera: Noctuidae), Falconia intermedia Distant (Hemiptera: Miridae) or Teleonemia scrupulosa Stål (Hemiptera: Tingidae) on lantana shoots. Density-dependent predation on F. intermedia and T. scrupulosa nymphs on lantana shoots was tested using Crematogaster sp. 2 colonies. In choice experiments Crematogaster sp. 2 colonies were offered F. intermedia or T. scrupulosa nymphs on potted lantana plants. Preliminary food trials confirmed that colonies foraged for protein, thereby validating results of no-choice experiments. Crematogaster sp.1 foragers removed 50% of F. intermedia nymphs, followed by 45% of H. laceratalis larvae and only 9% of T. scrupulosa nymphs. Foragers recruited most actively to H. laceratalis larvae and significantly more H. laceratalis biomass was removed than either F. intermedia or T. scrupulosa. A trade-off existed in prey size selection because larger larvae provided considerably more biomass but required forager cooperation and a longer time to subdue than did smaller prey. This increases both forager energy expense and mortality risk by other predators. This study showed that all Crematogaster sp. 1 colonies removed small (≤10mm) H. laceratalis larvae more frequently than larvae larger than 10mm. Thus, of these biological control agents, predators probably prefer small H. laceratalis larvae. Significantly more F. intermedia than T. scrupulosa nymphs were removed by Crematogaster sp. 1, while Crematogaster sp. 2 colonies removed comparable numbers of both agent species. Falconia intermedia nymphs' fast movement triggered a predatory response by these ant species. In contrast, the relatively immobile behaviour of T. scrupulosa nymphs was identified as a highly effective predator avoidance strategy. Since T. scrupulosa nymphs are unable to escape predators by moving, they appear to depend on the presence of alternative prey attracting predator attention. At high agent and/or forager density, T. scrupulosa nymphs attempted escape, but foragers identified them as prey once they moved and caught them. Predation on F. intermedia was also density dependent in that at high nymph and/or forager densities, escape routes were congested and nymphs were more easily caught. Survival of F. intermedia and T. scrupulosa nymphs in particular was low on ant-accessed shrubs in choice experiments and high on ant-excluded shrubs. It is likely that ants significantly depress F. intermedia populations in the field since besides predation, ant foragers probably interrupt F. intermedia feeding and ovipositioning. The combination of parasitism and predation on early instar larvae may explain why H. laceratalis occurs across lantana's range in South Africa but populations remain low. It is unlikely that T. scrupulosa nymphs are habitually preyed on by ant species unless they attract attention by being mobile. Although biological control of L. camara is influenced by climate and physiological defence mechanisms, this study has shown that predation by two ant species severely impacts leaf-feeding agents for L. camara. Thus, it is recommended that future selection of additional agents to control lantana should exclude leaf-feeding .

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.