Thesis (M.S.)--Mississippi State University. Department of Plant and Soil Sciences. / Title from title screen. Includes bibliographical references.

Thesis (Ph.D.) - University of KwaZulu-Natal, Pietermaritzburg, 2008. / Full text also available online. Scroll down for electronic link.

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xv, 126 p.; also includes graphics (some col.). Includes bibliographical references (p. 96-107). Available online via OhioLINK's ETD Center

Orientador: Nilza Maria Martinelli / Coorientadora: Ana Lúcia Benfatti Gonzalez Peronti / Banca: Odair Aparecido Fernandes / Banca: Valmir Antonio Costa / Resumo: A família Pseudococcidae é a segunda maior da Infraordem Coccomorpha, com cerca de 2000 espécies descritas. No Brasil, conhecidas popularmente como cochonilhas-farinhentas, compreendem a terceira maior família, com 77 espécies registradas, distribuídas em 22 gêneros. Destas, 32 espécies são conhecidas para o estado de São Paulo, sendo 30% polífagas e de origem exótica, infestando plantas de importância agrícola. O controle biológico é uma alternativa, e dentre os inimigos naturais os himenópteros parasitoides vêm sendo muito utilizados. O objetivo deste trabalho foi inventariar os micro-himenópteros parasitoides de 11 espécies de pseudococcídeos pragas, primarias ou secundarias, de várias culturas e plantas ornamentais no estado de São Paulo, como café, citros, pinha, goiabeira, entre outros, relacionando estes com seu hospedeiro, origem e distribuição geográfica. Os levantamentos dos himenópteros parasitoides foram realizados entre agosto de 2016 e agosto de 2017, de forma aleatória, em áreas rural e urbana de cinco municípios do estado São Paulo: Jales, Ribeirão Preto, Jaboticabal, São Carlos e Campinas. As espécies de pseudococcídeos amostrados para obtenção dos parasitoides foram: Dysmicoccus brevipes (Cockerell, 1893), Ferrisia virgata (Cockerell, 1893), Leptococcus capixaba Kondo, 2005, Leptococcus minutus (Hempel, 1932), Maconelicoccus hirsutus (Green, 1908), Nipaecoccus nipae (Maskell, 1893), Phenacoccus solenopsis Tinsley, 1898, Planococcus citri (Risso, 181... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The Pseudococcidae family is the second largest from the Coccomorpha Infraorder, with about 2000 described species. In Brazil, popularly known as mealybugs, it comprised the third largest family, with 77 species registered, distributed in 22 genera. From these, 32 species are known to the state of São Paulo, being 30% polyphagous from exotic origin, infesting plants of agricultural importance. Biological control is an alternative and among natural enemies, parasitoid Hymenoptera are being widely used. The objective of this work was to inventory the parasitoid microhymenoptera from 11 mealybug pest species, primary or secondary, from various crops and ornamental plants in the state of São Paulo, such as coffee, citrus, sugar-apple, guavas and others, relating these to their host, origin and geographical distribution. The parasitoid hymenopteran surveys were carried out between August 2016 and August 2017, in a random way, in rural and urban areas from five municipalities in the state of São Paulo: Jales, Ribeirão Preto, Jaboticabal, São Carlos and Campinas. The Pseudococcidae species sampled to obtain parasitoids were: Dysmicoccus brevipes (Cockerell, 1893), Ferrisia virgata (Cockerell, 1893), Leptococcus capixaba Kondo, 2005, Leptococcus minutus (Hempel, 1932), Maconelicoccus hirsutus (Green, 1908), Nipaecoccus nipae (Maskell, 1893), Phenacoccus solenopsis Tinsley, 1898, Planococcus citri (Risso, 1813), Planococcus minor (Maskell, 1897), Pseudococcus cryptus (Hempel... (Complete abstract click electronic access below) / Mestre

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)

Made available in DSpace on 2014-11-10T11:09:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-02-27Bitstream added on 2014-11-10T11:58:13Z : No. of bitstreams: 1 000793362.pdf: 2171550 bytes, checksum: cc9265ec01ac15bf4f3b278d742c1e9a (MD5) / Os besouros Carabidae (Coleoptera) apresentam grande importância para a agricultura como inimigos naturais de insetos pragas. No entanto, pouco se conhece sobre hábitos alimentares desses besouros. O presente trabalho visou verificar a ocorrência e o hábito alimentar de espécies de carabídeos associadas a plantas herbáceas floríferas nos diferentes Períodos fenológicos do algodoeiro colorido. O conteúdo alimentar foi avaliado em espécies presentes em cultura de algodoeiro colorido, Gossypium hirsutum L. raça latifolium Hutch., cultivar BRS verde, herbáceo, adjacente de plantas espontâneas e das plantas herbáceas floríferas (PHF) Lobularia maritima (L.) (Brassicaceae), Tagetes erecta L. (Asteraceae), Fagopyrum esculentum Moench (Polygonaceae). Algumas espécies de carabídeos ocorreram em diferentes Períodos fenológicos do algodoeiro e o número mais elevado de indivíduos verificou-se no período reprodutivo do algodoeiro. Os resultados obtidos no aparelho digestivo das espécies de carabídeos mostram que esses insetos podem se alimentar de vários tipos de conteúdo alimentar, relacionados com artrópodes e vegetais associados aos canteiros de PHF, nos diferentes períodos fenológicos do algodoeiro, podendo ser considerados predadores polífagos, e a morfologia do aparelho digestivo das nove espécies de carabídeos mostraram padrões de estruturas adaptadas para o tipo de dieta consumida por essas espécies / The Carabidae beetles (Coleoptera) have great importance to agriculture as natural enemies of insect pests. However, little is known about the content of these beetles feed. This study aimed to assess the occurrence and feeding habits of Carabid species associated with herbaceous plants (PHF) in different growth periods of coloured cotton. The food contents was evaluated in species that occurred in coloured cotton, Gossypium hirsutum L. latifolium Hutch., variety BRS green, herbaceous cotton, adjacent weeds and PHF Lobularia maritima (L.), Tagetes erecta L., Fagopyrum esculentum Moench. Some species of Carabid beetles occurred at different cotton growth periods and the highest number of individuals was found in the cotton reproductive stage. The results showed many types of feed contents ingested by the Carabidae beetles gut tract, like arthropods and vegetable associated with PHF in different growth periods of cotton and can be considered polyphagous predators. The gut tract morphology showed that nine species of Carabid beetles showed standards structures adapted to the type of diet ingested

Orientador: Francisco Jorge Cividanes / Banca: Antonio Carlos Busoli / Banca: Sergio Ide / Resumo: Os besouros Carabidae (Coleoptera) apresentam grande importância para a agricultura como inimigos naturais de insetos pragas. No entanto, pouco se conhece sobre hábitos alimentares desses besouros. O presente trabalho visou verificar a ocorrência e o hábito alimentar de espécies de carabídeos associadas a plantas herbáceas floríferas nos diferentes Períodos fenológicos do algodoeiro colorido. O conteúdo alimentar foi avaliado em espécies presentes em cultura de algodoeiro colorido, Gossypium hirsutum L. raça latifolium Hutch., cultivar BRS verde, herbáceo, adjacente de plantas espontâneas e das plantas herbáceas floríferas (PHF) Lobularia maritima (L.) (Brassicaceae), Tagetes erecta L. (Asteraceae), Fagopyrum esculentum Moench (Polygonaceae). Algumas espécies de carabídeos ocorreram em diferentes Períodos fenológicos do algodoeiro e o número mais elevado de indivíduos verificou-se no período reprodutivo do algodoeiro. Os resultados obtidos no aparelho digestivo das espécies de carabídeos mostram que esses insetos podem se alimentar de vários tipos de conteúdo alimentar, relacionados com artrópodes e vegetais associados aos canteiros de PHF, nos diferentes períodos fenológicos do algodoeiro, podendo ser considerados predadores polífagos, e a morfologia do aparelho digestivo das nove espécies de carabídeos mostraram padrões de estruturas adaptadas para o tipo de dieta consumida por essas espécies / Abstract: The Carabidae beetles (Coleoptera) have great importance to agriculture as natural enemies of insect pests. However, little is known about the content of these beetles feed. This study aimed to assess the occurrence and feeding habits of Carabid species associated with herbaceous plants (PHF) in different growth periods of coloured cotton. The food contents was evaluated in species that occurred in coloured cotton, Gossypium hirsutum L. latifolium Hutch., variety BRS green, herbaceous cotton, adjacent weeds and PHF Lobularia maritima (L.), Tagetes erecta L., Fagopyrum esculentum Moench. Some species of Carabid beetles occurred at different cotton growth periods and the highest number of individuals was found in the cotton reproductive stage. The results showed many types of feed contents ingested by the Carabidae beetles gut tract, like arthropods and vegetable associated with PHF in different growth periods of cotton and can be considered polyphagous predators. The gut tract morphology showed that nine species of Carabid beetles showed standards structures adapted to the type of diet ingested / Mestre

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Science. Johannesburg, March 2017. / Water hyacinth (Eichhornia crassipes) is an example of an alien invasive plant, threatening ecosystems around the world. Taking into consideration all the negative impacts caused by the proliferation of water hyacinth, many control measures have been implemented to manage this weed. These include mechanical control, chemical control and biological control. But in recent years, the focus has shifted towards natural enemies for control (biological control) of water hyacinth because they have many advantages for environmental safety. However, in South Africa, success is limited in most parts of the country. Factors affecting the success of biological control of water hyacinth in South Africa have been attributed in part to weather conditions. Therefore, further studies and other strategies are needed to reinforce the biological control of water hyacinth. This is why this research investigated the influences of temperature on Neochetina eichhorniae larvae feeding and development on water hyacinth, to contribute to the future management of water hyacinth biological control. To measure the effect of temperature on the feeding and development of Neochetina eichhorniae larva, experiments were conducted at four fixed temperatures (15 °C, 20 °C, 25 °C, and 30 °C). Larval feeding is expected to be greater and the development faster at warm temperatures compared with cold temperatures. The results of this study confirmed that, both feeding and larval development increased with an increase in temperature. The highest larval feeding damage was recorded at 30°C and the lowest at 15°C. Similar to the feeding of larvae, warmer temperatures were more favourable to the growth of larvae than cold temperatures; all larvae found at 30°C were in their third instars (with 0.72 mm being the biggest headwidth found) while all larvae at 15°C were in the first instars (with 0.28 mm being the smallest headwidth found). Even if the optimal temperature for larval performance took place at 30 °C (with a high amount of biomass removal), it was at 25 °C that the larvae had a larger effect on the growth of water hyacinth. Larval feeding damage reduced the growth of water hyacinth by 30 % at 25 °C and only affected 24 % of water hyacinth growth at iv 30 °C. Therefore, for the biocontrol of water hyacinth, the ideal temperature to slow the progression of the weed will be recommended at between 25- 30 °C. / LG2017

Thesis (MEng) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: As overpopulation threatens the world’s ability to feed itself, food has become an invaluable resource. Unfortunately, almost a third of the food produced for human consumption is lost annually. Pests including insects, phytopathogens and weeds are responsible for more than a third of the annual major crop losses suffered around the world. The majority of current post-harvest control strategies employ synthetic agents. These compounds, however, have been found to be detrimental to the environment as well as human health, which has led researchers to investigate alternative strategies. Biocontrol agents are environmentally compatible, have a lower toxicity and are biodegradable, making them an attractive alternative to the synthetic control agents. The lipopeptides produced by Bacillus spp. in particular, have shown great potential as biocontrol agents against various post-harvest phytopathogens. Most biocontrol strategies apply the biocontrol organism, for example Bacillus, directly, whereas this study focused on the use of the lipopeptide itself as an antifungal agent. This is advantageous as the lipopeptides are less sensitive to their surroundings, such as temperature and pH, compared to living organisms, allowing for the production of a standardized product. This study investigated the production of the Bacillus lipopeptides surfactin, fengycin and iturin under controlled batch conditions. Parameters increasing lipopeptide production were quantified, focussing on antifungal lipopeptides (iturin and fengycin), and lipopeptide production was optimized. Experiments were performed in a fully instrumented 1.3 L bench-top bioreactor and lipopeptide analyses were performed via high pressure liquid chromatography (HPLC) and liquid chromatography-mass spectroscopy (LC-MS). After screening four Bacillus spp., Bacillus amyloliquefaciens DSM 23117 was found to be the best antifungal candidate. This was based on it outperforming other candidates in terms of maximum antifungals produced, Yp/x,antifungals (yield per cells), and antifungal productivity. Nitrate, in the form of NH4NO3, was critical for lipopeptide production and an optimum concentration was observed above which the CDW (cell dry weight) no longer increased significantly and both μmax (maximum specific growth rate, h-1) and lipopeptide production decreased. For μmax, the optimum NH3NO4 concentration was 10 g/L and for lipopeptides it was 8 g/L. At these respective NH4NO3 concentrations μmax = 0.58 (h-1), the maximum antifungals (fengycin and iturin) were 285.7 mAU*min and the maximum surfactin concentration was 302 mg/L. The lipopeptides produced by B. amyloliquefaciens, the antifungals (fengycin and iturin) and surfactin, are secondary metabolites, regardless of the optimization treatment, i.e. increased NH4NO3 concentrations. Using 30% enriched air extended the nitrate utilization period, suggesting that when increasing supply concentration, more oxygen was available to act as electron acceptors, allowing nitrate to be used for lipopeptide production. The number of iturin and fengycin homologues generally increased with an increase in nitrate concentration. This suggested that process conditions, such as nitrate concentration, can be used to manipulate homologue ratios, allowing for the possibility to tailor-make biocontrol-agent upstream, during the production process, and possibly increase the efficacy of the biocontrol strategy. The lipopeptides produced by B. amyloliquefaciens showed complete inhibition against Botryotinia fuckeliana and diminished the growth capabilities of Botrytis cinerea. No inhibition was observed against Penicillium digitatum. These results indicate potential of the biocontrol strategy, although scale-up and fed-batch studies are recommended, especially when considering commercial implementation. Studies regarding the lipopeptide application method, i.e. a single application or multiple applications, should also be investigated as this will influence the efficacy of the lipopeptides against the target organisms. / AFRIKKANSE OPSOMMING: Met oorbevolking wat die wêreld se vermoë om die groeiende bevolking te onderhou belemmer, het dit noodsaaklik geword om huidige voedselbronne te beskerm. Daar word beraam dat een derde van die voedsel wat wêreldwyd geproduseer word vir menslike verbruik verlore gaan elke jaar. Verder is insekte, plantpatogene en onkruide verantwoordelik vir meer as ‘n derde van die verliese rakend jaarlikse oeste. Meeste bestaande na-oes beheermetodes maak gebruik van sintetiese stowwe. Ongelukkig kan hierdie verbindings nadelig wees vir die omgewing sowel as menlike gesondheid. Navorsers het hulsef dus toespits daarop om alternatiewe beheermetodes te ondersoek. Bio-beheermetodes is omgewingsvriendelik sowel as bio-afbreekbaar, wat hulle ideale alternatiewe maak vir die sintetiese stowwe. Bacillus spp. lipopeptiede het veral hoë potensiaal getoon as bio-beheermiddels teen verskeie na-oes plantsiektes. Meeste bio-beheermetodes wend die biobeheer organisme, soos Bacillus, direk aan, waar hierdie studie op die gebruik van lipopeptiede as ‘n beheermiddel gefokus het. Die voordeel is dat lipopeptidiede minder sensitief is vir hul omgewings, soos temperatuur en pH, i.v.m. organismes en die moontlikheid bied van ‘n gestandardiseerde produk. Hierdie studie het die produksie van spesifieke Bacillus lipopeptide, naamlik surfactin, fengycin en iturin, onder beheerde lottoestande ondersoek. Parameters wat lipopeptied produksie verhoog is gekwantifiseer, spesifiek antifungiese middels (iturin en fengycin) en lipopeptied produksie is geoptimeer. Eksperimente is uitgevoer in ‘n 1.3 L bioreaktor en lipopeptiedanaliese is met behulp van hoë druk vloeistof chromatografie en vloeistofchromatografie-massa spektroskopie uitgevoer. Van die vier moontlike Bacillus spp., was Bacillus amyloliquefaciens DSM 23117 die mees belowende antifungus-produserende kandidaat. Dit het beter resultate gelewer in terme van maksimale antifungiese produksie, Yp/x,antifungies (opbrengs per sel) asook antifungiese produktiwiteit. Nitraat, in hierdie geval NH4NO3, was noodsaaklik vir lipopeptied produksie en ‘n optimale konsentrasie is waargeneem waarbo die seldigtheid nie meer beduidend toegeneem het nie en beide die μmax (maksimale spesifieke groei tempo, h-1) en lipopeptied produksie afgeneem het. Die optimale NH4NO3 konsentrasie vir μmax was 10 g/L en vir lipopeptiedproduksie was 8 g/L. By 10 g/L NH4NO3 was μmax = 0.58 (h-1) en by 8 g/L was die maksimale antifungiese produksie (fengycin en iturin) 285.7 mAU*min en die maksimale surfactin produksie 302 mg/L onderskeidelik. Die lipopeptide, die antifungiese middels (fengycin en iturin) en surfactin, geproduseer deur B. amyloliquefaciens is sekondêre metaboliete, ongeag van die optimerings-behandelinge wat toegepas word, soos ‘n verhoging in NH4NO3 konsentrasie. Die gebruik van 30% verrykte suurstof het die nitraat verbruikingsperiode verleng, wat voorgestel het dat met die verryking, meer suurstof beskikbaar was om te dien as finale elektron ontvanger en sodoende die nitraat beskikbaar te stel vir lipopeptied produksie. Iturin en fengycin homoloë, oor die algemeen, het toegeneem soos wat die nitraat konsentrasie verhoog is. Hierdie resultate dui daarop dat prosestoestande, soos nitraat konsentrasie, gebruik kan word om die verhouding waarin lipopeptied homoloë geproduseer word te manipuleer. Hierdie resultate dui op die potensiaal vir die stroomop produksie van ‘n unieke bio-beheermiddel, wat die effektiwiteit van die bio-beheermetode moontlik sal verhoog. Die geproduseerde lipopeptiede het totale inhibisie getoon teen Botryotinia fuckeliana en ook fungiese aktiwiteit belemmer met Botrytis cinerea. Geen inhibisie is getoon teen Penicillium digitatum nie. Hierdie resultate toon die potensiaal van die bio-beheermetode, maar ‘n opskalerings-studie asook ‘n voerlot studie word aanbeveel, veral met die oog op moontlike kommersiële implementering van die strategie. Verdere studies met betrekking tot die aanwendingsmetode van die lipopeptiede moet ook verder ondersoek word, m.a.w. enkel teenoor menigte aanwendigs, aangesien dit die effektiwiteit van die lipopeptiede teen die teikenorganismes sal beïnvloed.

Thesis (PhD (Agric))--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Biological control studies were conducted with isolates of entomopathogenic fungi Beauveria bassiana and Metarrhizium anisopliae from Ethiopia and South Africa against the spotted stem borer Chilo partellus. The study was conducted from April 2002 to April 2003, at the department of Entomology and Nematology, University of Stellenbosch, South Africa. The objectives were to screen these isolates for pathogenicity and to determine the susceptibility of different larval instars; to study the effect of temperature on fungal development and virulence; to investigate food consumption of fungus treated larvae; to determine compatibility of fungal isolates with insecticides; to study the effect of exposure methods and diets on larval mortality; and to evaluate promising isolates under greenhouse conditions using artificially infested maize plants. Four isolates of B. bassiana and six isolates of M. anisopliae were tested against second instar larvae. Of these isolates, B. bassiana (BB-01) and M. anisopliae (PPRC-4, PPRC-19, PPRC-61 and EE-01) were found to be highly pathogenic inducing 90 to 100 % mortality seven days after treatment. In subsequent assays, the fungal isolates were tested against third, fourth, fifth and sixth instar larvae. Second and sixth instar larvae were more susceptible to these isolates than third, fourth and fifth instar larvae. Conidial germination, radial growth and sporulation of the isolates PPRC-4, PPRC-19, PPRC-61, EE-01 and BB-01 were retarded at 15 and 35 0C. A suitable temperature range for the isolates was from 20 - 30 0C. At 25 and 30 0C the isolates induced 100 % mortality to second instar larvae within four to six days. Second and third instar C. partellus larvae were treated with the isolates PPRC-4 and BB-01, and daily consumption of maize leaf was measured. Treatment with the fungi was associated with a reduction in mean daily food consumption. In in-vitro studies, five concentrations (0.1 ppm, 1 ppm, 5 ppm, 10 ppm, and 100 ppm active ingredients) of the insecticides benfuracarb and endosulfan were tested with the isolates PPRC-4, PPRC-19, PPRC-16, EE-01 and BB-01. Increasing the concentration of the insecticides adversely affected germination, radial growth and sporulation of the isolates. In in-vivo studies combining the fungi, PPRC-4 and BB-01,with low concentrations (1 and 5 ppm a.i.), of the insecticides increased the mortality of third instar larvae from 65 to 100 %. Larvae sprayed directly with conidia, exposed to conidia treated leaves and dipped into conidial suspensions suffered high mortality of 98 to 100 %. Larvae exposed to treated leaves and larvae sprayed directly with conidia produced high numbers mycoses in cadavers. Exposure of larvae to treated leaves yielded high sporulation. At a low conidial concentration (1.25x107 conidia/ml), mycosis and sporulation were high. The optimum temperature was 20 0C for mycosis and 15 0C for sporulation. In greenhouse trails, a conidial suspension of 2 x 108 conidia/ml of the pathogenic isolates was sprayed on 3 to 4 week-old maize plants infested with 20 second instar larvae per plant. This resulted in suppression of foliar damage. Treatment with the fungi also reduced stem tunneling and deadheart. In addition, fungal treatment increased mean plant fresh and dry biomass compared to untreated control plants. In general, results from laboratory and greenhouse studies indicated that there was good potential for the use of these fungal isolates for controlling C. partellus larvae. / AFRIKAANSE OPSOMMING: Biologiese beheerstudies is uitgevoer met isolate van die insekpatogeniese swamme, Beauvaria bassiana en Metarrhizium anisopliae teen die gespikkelde stamboorder, Chilo partellus. Die doelwitte was om hierdie isolate te evalueer vir patogenesiteit; die vatbaarheid van verskillende larvale instars teenoor hulle te bepaal; die invloed van temperatuur op swamontwikkeling en virulensie te bepaal; die voedsel inname van swambehandelde larwes te ondersoek; die verenigbaarheid van die swamisolate met insektedoders te bepaal; die invloed van blootstellingsmetodes en diëte op larvale mortaliteit; en om belowende isolate in glashuisproewe te evalueer met gebruik van kunsmatig besmette mielieplante. Vier isolate van B. bassiana en ses isolate van M. anisopliae is teen tweede instar larwes getoets. Uit dié isolate is B. bassiana (BB-01) en M. anisopliae (PPRC-4, PPRC- 19, PPRC-16 en EE-01) as hoogs patogenies bevind. Hulle het 90 tot 100 % mortaliteit na sewe dae veroorsaak. In daaropvolgende essays, is die swamisolate teen derde, vierde, vyfde en sesde instar larwes getoets. Tweede en sesde instar larwes was gevoeliger vir die isolate as die derde, vierde en vyfde instar larwes. Spoorkeming, radiale groei en sporulasie van die isolate PPRC-4, PPRC-19, PPRC-61, EE-01 en BB-01, is by 15 en 35 0C vertraag. ‘n Aanvaarbare temperatuurreeks vir die isolate is vanaf 20 tot 30 0C. By 25 en 30 0C het die isolate 100 % mortaliteit teen tweede instar larwes binne vier tot ses dae geïndusseer. Tweede en derde instar C. partellus larwes is met die isolate PPRC-4 en BB-01 behandel en die daaglikse inname van mielieblare gemeet. Behandeling met die swamme is met ‘n afname in die gemiddelde voedselinname geassosieer In in-vitro studies is vyf konsentrasies (0.1 dpm, 1 dpm, 5 dpm, 10 dpm en 100 dpm aktiewe bestandele) van die insekdoders, benfuracarb en endosulfan getoets saam met die isolate PPRC-4, PPRC-19, PPRC-16, EE-01 en BB-01. ‘n Toename in die konsentrasie van die insekdoders het ontkieming, radiale groei en sporulasie van die isolate benadeel. In in-vitro studies het die kombinering van die die swamme, PPRC-4 en BB-01, met lae konsentrasies (1 en 5 dpm a.b.) van die insekdoders mortaliteit van derde instar larwes vanaf 65 tot 100 % laat toeneem. Larwes wat direk met spore gespuit is, aan behandelde blare blootgestel is en in spoorsuspensies gedoop is het tot hoë mortaliteit gelei, (98 tot 100 %). Blootstelling aan behandelde blare saam met ‘n lae konidiakonsentrasie, 1.25x106 spore/ml) en ‘n temperatuur van 15 tot 20 0C het tot hoë swammikose en sporulasie in kadawers gelei. In glashuisproewe, is ‘n spoorsuspensies van 2 x 108 spores/ml van die patogeniese isolate op 3 tot 4 weekoud mielieplante wat met 20 tweede instar larwes per plant besmet is gespuit. Dit het blaarskade onderdruk. Behandeling met die swamme het ook stamtonnels en dooiehart verminder. Boonop het swambehandeling die vars- en droë plantbiomassa laat toeneem in vergelyking met die onbehandelde kontrole plante. Oor die algemeen het resultate van laboratorium- en glashuisproewe getoon dat daar goeie potensiaal is vir die gebruik van hierdie swamisolate vir die beheer van C. partellus larwes.