Resumo: O interesse pelo controle biológico de nematóides vem aumentando ano após ano, estimulado pelas crescentes restrições ao uso de agrotóxicos. Entre os agentes do controle biológico de nematóides, os fungos predadores vêm se destacando, dada a facilidade de crescimento em meios artificiais e substratos diversos e a comprovada eficácia. No presente estudo, confirmou-se que espécies de Arthrobotrys e de Monacrosporium estão entre os fungos nematófagos mais comuns nos solos do Brasil. Esses fungos crescem em subprodutos da agroindústria, potencializando a formulação desses agentes a baixo custo e pode tornar-se o recurso mais vantajoso para o manejo de nematóides em cultivos de hortifrutigranjeiros em volta de centros urbanos. Bagaço de cana misturado com farelo de arroz, na proporção de 2:1, é um substrato adequado à formulação de fungos nematófagos. Para o cultivo de alface, uma única aplicação, antes do plantio, é suficiente para o manejo dos nematóides. A adição de formulações dos fungos ao substrato para a produção de mudas pode facilitar a utilização desse recurso, e formulações contendo mais de uma espécie com habilidades predatórias diferentes, incluindo parasitos de ovos, podem ser mais eficazes que formulações de uma única espécie. A especificidade dos fungos dificulta o comércio de formulações desses agentes, dado o risco de comprometimento à credibilidade dos produtos, se formulações não-específicas para os nematóides que ocorrem em certas áreas, forem utilizadas. Por conseguinte, as formulações desses agentes são mais adequadas para a distribuição assistida, já que os nematóides que ocorrem nos locais onde serão empregadas, podem ser previamente identificados. / Abstract: The interest in the biological control of nematodes is increasing year after year, stimulated by the increasing restrictions to the use of chemical defensives. Among the agents for the biological control of nematodes, the predators fungi have become the group of higher interest since they grow easily on different kinds of material and they also present known efficacy. In the present study, it was demonstrated that species of Arthrobotrys and Monacrosporium are among the most common nematophagous fungi in Brazilian soils. These fungi grow on by-products of the agroindustry, making formulations of these agents of low cost and can become the most advantageous resource for the nematode control in vegetable production areas around urban centers in Brazil. Sugar cane bagasse mixed with rice bran in the ratio of 2:1 is an adequate substratum for the formulation of nematophagous fungi. For the lettuce culture, only one application, before the planting date, is enough for the control of nematodes. The addition of fungi to the substratum for the production of seedlings in nurseries can facilitate the use of this resource. Formulations containing more than one species with different predatory abilities, including egg parasites, can be more efficient than formulations with only one species. The specificity of the fungi makes difficult the commerce of formulations of these agents, since the risk of unsuccessful use can put down the credibility on the products, if non-specific formulations for the nematodes that occur in certain areas are used. Therefore, the formulations of these agents are more suitable for attended distribution, since the nematodes that occur in places where the formulation will be used can be previously identified. / Orientador: Jaime Maia dos Santos / Coorientador: José Carlos Barbosa / Banca: Clélia Aparecida Iunes Lapera / Banca: Marineide Mendonça Aguillera / Banca: Carlos Amadeu Leite de Oliveira / Banca: Júlio César Galli / Doutor

Orientador: Sérgio Antonio de Bortoli / Banca: Nilza Maria Martinelli / Banca: Elisângela de Souza Loureiro / Resumo: Este trabalho teve como objetivo avaliar a capacidade predatória, aspectos comportamentais, reprodutivos e estabelecer a curva de resposta funcional do predador O. insidiosus predando ovos e lagartas de primeiro ínstar de Diatraea sacchara/is, P/utella xy/ostella, Spodoptera frugiperda e Anticarsia gemmatalis, e ninfas de terceiro/quarto ínstar de Aphis gossypii. Além destas avaliações, observou-se alguns aspectos reprodutivos de O. insidiosus, todos em função das diferentes densidades de A. gossypii. Para as espécies estudadas o predador apresentou curva de resposta funcional tipo 11, mostrando uma tendência de estabilização nas densidades mais altas. A taxa de ataque foi de 42,16; 9,35 e 22,81 ovos/hora e o tempo de manipulação de 1,56; 1,91 e 1,74 horas, para S. frugiperda, A. gemmatalis e P. xy/ostella, respectivamente. Observou-se também uma baixa capacidade predatória do O. insidiosus sobre ovos de D. saccharalis, proporcionando valores quase nulos para taxa de ataque e tempo de manipulação. A taxa de ataque foi de 15,55; 18,06; 1,77 e 3,68 lagartas/hora, e o tempo de manipulação de 2,13; 1,32; 0,86 e 1,99 horas para S. frugiperda, A. gemmatalis, D. saccharalis e P. xy/ostella, respectivamente. Para A. gossypii a taxa de ataque foi de 0,10 pulgão/hora e tempo de manipulação de 1, 82 h. O predador passou de 3,10 a 4,08 h se alimentando de seiva no nectário foliar do algodoeiro, não tendo a densidade da presa influência direta sobre esse comportamento. A proporção de postura por fêmea foi crescente até 10 ninfas, enquanto a proporção do número de ovos por postura aumentou com o aumento de presas disponíveis. / Abstract: The aim of this research was to evaluate the predatory capacity, behavior aspects and to establish O. insidiosus functional response curve preying Diatraea saccharalis, P/utella xy/ostella, Spodoptera frugiperda and Anticarsia gemmatalis eggs and first instar larvae, and Aphis gossypii third/fourth instar nymphs. By these evaluations it was observed some reproductive aspects of O. insidiosus, in function of A. gossypii different densities. The functional response type 11 was observed for ali species, showing a tendency of stability in the highest densities. The attack rate was 42.16, 9.35 e 22.81 eggs/hour and the handling time 1.56, 1.91 e 1.74 hours for S. frugiperda, A. gemmatalis and P. xy/ostella, respectively. It was also verified a low predatory capacity of O. insidiosus on D. saccharalis eggs, with almost null values for attack rate and handling time, making them despicable. The attack rate was 15.55,18.06,1.77 and 3.68Iarvae/hour, and the handling time 2.13, 1.32,0.86 e 1.99 hours for S. frugiperda, A. gemmatalis, D. saccharalis and P. xy/ostella, respectively. For A. gossypii the attack was 0.10 aphid/hour and the handling time 1.82 h. The predator teal on cotton sap and foliar nectary for 3.10 to 4.08 h, and there was no straight influence of the prey on this behavior. The egg-Iaying by female was crescent, until 10 nymphs, while the egg rate by egg-Iaying increased as the number of preys increased. / Mestre

Development of microbial herbicides is constrained by unreliability in the field where conditions are often sub-optimal for infection. Crucially, sufficient moisture, often dew, is required to establish infection. Two model systems, Colletotrichum dematium (Pers. ex Fr. ) Grove on Chenopodium album L. and Mycocentrospora acerina (Hartig) Deighton on Viola arvensis Murr., have been investigated and formulation requirements for each system identified, principally to reduce the dew period necessary for infection. Effects of adjuvants (surfactants, stickers and humectants) on spore germination and appressorium formation were investigated in vitro. Few were toxic and then, principally, at high concentration. The surfactants Tween 40,60 and 80 were compatible with both pathogens. Similarly, the stickers acacia, ghatti, guar, karaya, locust bean and xanthan gums and low viscosity alginic acid were all non-toxic as was the humectant glycerol. Each pathogen reacted differently to the adjuvants and any potential microbial herbicide will need individual matching of adjuvants to give an effective formulation. A working formulation (rapeseed oil-in-water (1: 10 v/v) emulsion using 0.1 % v/v Tween 40 as the emulsifier) was found to reduce the dew period requirement of M. acerina from 36 to 18 hours. The formulation protected spores from desiccation for 24 hours after application, or for 16 hours following a sub-optimum dew period occurring immediately after application. Scanning electron microscopy showed that the applied spores, and the developing mycelium, were immersed in the oil deposit. Transmission electron microscopy of sections through formulation deposits on the leaf revealed that some inversion of the emulsion, to form a water-inoil deposit, had occurred, suggesting a mechanism of protection against desiccation. The oil phase infiltrated the cortical intercellular spaces only when the leaf was infected. This intercellular oil contained more water than that on the leaf surface. Emulsion-formulation applied to run-off with an 'air brush', consistently gave significantly better weed control under sub-optimal dew conditions than a formulation of surfactant only. When applied with a conventional hydraulic nozzle at 400 1 ha" the emulsion was only occasionally superior to the surfactant alone. Such interactions require further in-depth investigation. The importance of correct inoculum placement for maximum effectiveness, independent of formulation type, was highlighted. Unless all meristems are killed, survivors quickly grow, despite the death of neighbouring leaves and petioles, and the weed suffers merely a growth check. Formulation as emulsion improved diseasee stablishmenta nd diseasee xpressioni n the target weedo nly in somec ircumstancesF. urther researchin to spraya pplicationm ethodsa ndt heir interactions with formulation, host and environment is clearly necessary

Dutch elm disease (DED) is a debilitating wilt disease that has decimated elm populations globally. The current pandemic of this disease is caused by the ascomycete fungal pathogen Ophiostoma novo-ulmi. A number of strategies have been used to attempt to mitigate the effects of DED but none have met any sustainable success, and the disease continues to have severe ecological and economic impacts. Consequently, research focus has turned to the development of control strategies at the genetic level. One such genetic strategy is the use of naturally occurring fungal viruses (mycoviruses) to induce hypovirulence in their fungal hosts. Hypovirulence, or attenuation of fungal pathogenicity using mycoviruses, has been well studied in other systems but has yet to be developed for O. novo-ulmi. A candidate virus, OnuMV1c, was found in an isolate of O. novo-ulmi (93-1224) at the western Canadian disease front and its genome was sequenced. OnuMV1c is a mitochondrial virus and has a 3.1 kb single-stranded positive RNA genome that encodes an RNA-dependent RNA polymerase (RdRp) involved in its replication as a double-stranded RNA molecule. It exists in O. novo-ulmi mitochondria in both its single-stranded and double-stranded forms. Our research group identified OnuMV1c as a potential candidate for biological control of Dutch elm disease. Our long-term research goal is to use the virus as a means to activate the RNA interference pathway of O. novo-ulmi, leading to down-regulation of genes involved in pathogenicity. If OnuMV1c is engineered such that it carries an RNA interference cassette in addition to its own complement of genes, it could act as an enhanced hypovirus. RNA interference (RNAi) is a cytoplasmic process, and therefore in order to use OnuMV1c for RNAi the viral genome needed to be reprogrammed such that it could be expressed in the cytoplasm rather than the mitochondria. The objectives of my master’s research were to 1) genetically engineer OnuMV1c to express in the cytoplasm using a cDNA reverse genetics approach, and 2) test the functionality of the re-engineered cDNA OnuMV1c virus (MV1cCyt). The first objective was accomplished by modifying codons in the RdRp sequence of OnuMV1c such that the sequence could be translated in the cytoplasm. This genetically engineered cytoplasmic version of OnuMV1c, named MV1cCyt, was flanked with exogenous promoter and terminator sequences to drive its transcription. The entire construct was engineered as a cDNA molecule and was cloned into the fungal transformation vector pAN7-1, which was used to transform O. novo-ulmi protoplasts. The second objective was achieved through the use of strand-specific RT-PCR, a technique that allowed the detection of both the positive and negative strands of MV1cCyt. Results indicated that while four individual cell lineages contained MV1cCyt cDNA stably integrated into the nuclear genome, only one transformant was able to produce double-stranded MV1cCyt RNA. These results have important implications for the use of OnuMV1c as an engineered hypovirus and represent the first step towards the development of a biological control strategy for Dutch elm disease. / Graduate

Hakea sericea Schrader was introduced to South Africa from Australia and has become a major problem in nearly all the coastal mountain ranges of the Cape Province. The hakea seed-moth, Carposina autologa Meyrick was released in South Africa for the biological control of H. sericea. The impact of the moth on the canopy-stored seeds of H. sericea was evaluated at two study sites in the south-western Cape over three years. The moth has reduced the accumulated seeds at the two study sites by 59.4% and 42.6%, respectively. The moth has shown a surprising ability to disperse and establish new colonies at low population levels. Factors contributing to the slow colonization of C. autologa in South Africa was investigated. The moths appear to be unable to distinguish between healthy and previously attacked fruits; 42.5% of the eggs were laid on attacked fruits. Only 13.1% of the healthy fruits with eggs yielded mature larvae. The high pre-penetration mortality found in the present study is similar to that found in Australia. The effect of the indigenous fungus, Colletotrichum gloeosporioides (Penz.) Sacc., on both H. sericea and C. autologa was investigated. H. sericea trees and branches that die as a result of fungus cause the accumulated fruits on the affected trees or branches to dehisce. This seed loss occurs at a crucial stage during C. autologa larval development. Only 42.1% and 33.0% of the trees were found to be healthy at the two study sites, respectively. One seed crop will always be available for regeneration, since recruitment is linked to fires, and wild-fires occur at a stage when the latest seed crop has escaped attack by c. autologa. C. autologa was released at six sites in the south-western Cape by attaching egg-bearing follicles to healthy fruits in the field. Three release sites were evaluated the year following release to determine whether the moth established or not. The role of C. autologa in the H. sericea biological control programme is discussed. Although seed destruction by C. autologa is not severe, it is expected to contribute to the control of H. sericea.

Jointed Cactus, Opuntia aurantiaca Lindley (see frontispiece), is the most important weed plant in South Africa, infesting approximately, 1,2 X 10¹° M² and costing approximately R240 000 per annum. Tordon herbicide effectively kills jointed cactus bushes to which it is applied. However, apart from being expensive and damaging to beneficial vegetation, spray programmes have not successfully controlled the weed because most small O. aurantiaca plants are impossible to detect in the field. Biological control may provide a solution to the problem. Two insects, the cochineal bug, Dactylopius austrinus De Lotto and the pyralid moth, Cactoblastis cactorum Berg., already exercise a degree of control over the weed. The introduction into South Africa of other natural enemies such as Zophodia tapiacola (Dyar) from Argentina, South America, may reduce the density of jointed cactus to below an acceptable economic threshold. Any insect considered for release should not colonise and destroy beneficial plants of which the culivated spineless cacti are the most vulnerable. Pre-release studies on Z. tapiacola have shown that it can only colonise a few species of low growing cacti and that it will not damage the large spineless cacti or other desirable plants. Further, the moths are relatively fecund and each larva destroys significant amounts of O. aurantiaca during its development. Consequently, Z. tapiacola is not only considered safe for release but it has the potential to act as a successful biological control agent of O. aurantiaca in South Africa.

1. Fifteen parasite species comprising the T. erytreae complex in Salisbury are listed. 2. Detailed, illustrated accounts are given of the biology of two primary parasites, Tetrastichus Pradiatus Waterston and Psyllaephagus pulvinatus (Waterston ), and their main hyperparasite, Aphidencyrtus cassatus Annecke. 3. The biology of the remaining twelve less important hyperparasites is briefly described and illustrated. 4. Keys are given to the adults, pupae and pupal remains of the parasites. 5 . The population fluctuations of T. erytreae and its parasites, as determined from field studies in the Salisbury area, are reported . 6. The interrelationships between T. erytreae and its parasites are summarised and discussed. Summary, p. 89.

Invasive alien tree species have negative environmental and economic impacts throughout the world. For example, black wattle (Acacia mearnsii) threatens native habitats by competing with and so repressing or excluding indigenous vegetation: in this way it replaces grass communities, reduces biodiversity, and increases water loss from riparian zones, thereby fundamentally damaging the ecosystem. The Acacia mearnsii threat requires urgent attention: effective control and management is urgently required if these deleterious impacts are to be reversed or prevented. The present study was conducted in the Elliot and Ugie communities situated in the Sakhisizwe and Elundini Local Municipalities. The objective of this study was to design integrated, efficient and cost-effective methods to help farmers and members of these communities with control and management of alien plant invasions. Further the study aimed to evaluate the implementation and efficacy of Working for Water (WfW) initiatives in poverty alleviation, and skills development: in addition the study attempted to assess WfW inputs as regards relevant legislation aimed at combating major wattle invasions. Mixed methodological approaches were employed, utilizing both qualitative and quantitative techniques. Questionnaire surveys, semi-structured interviews, use of photos, content analyses of local documents and experimental field work were all employed in order to collect and interpret data for the study. The study reveals that mechanical control and rehabilitation in combating should provide efficient and cost-effective methods for proper management of rangelands. Moreover the National Department of Agriculture, Forestry and Fisheries (DAFF) should be urged to devise and enforce legislation that will help to ensure sustainable control and management of black wattle through conservation of the natural environment. Furthermore funds should be made available for wattle eradication programmes so as alleviate poverty by creating more job opportunities for members of poor communities.

No description available.

This thesis was designed to address three seldom studied aspects of the relationship between herbivores and vegetational diversity. 1. Interactions between vegetational diversity and herbivore mortality due to predation were assessed by experimentally manipulating both the species diversity of plants and the densities of a common generalist predator, the spider Enoplagnatha ovata. 2. The importance of plant size to herbivore densities was examined by quantifying plant size (measured as plant height, width, leaf area and growth rates) and adjusting for it through covariate analysis. 3. Differences in population responses of several species of herbivores to both vegetational diversity and a predator, were compared by concurrently studying four lepidopterans. The main experiment used a two factor design, with two planting treatments and two predator treatments. The planting treatments consisted of plots planted with monocultures of brussels sprouts (Brassica oleraceae) and dicultures of brussels sprouts intercropped with peppermint (Mentha piperita). The natural enemy treatments involved augmentations of E ovata in some plots and untreated controls. Two of the herbivores studied, Plutella xylostella and Pieris rapae are monophagous lepidopterans, specializing on crucifers, while the others, Autographa californica and Mamestra configurata are polyphagous. For two species, P. xylostella and M. configurata responses to augmentations of the spider, E. ovata. were different in monocultures and dicultures. Reduced densities of these two species were found in monoculture plots with added spiders; in dicultures increased densities were found in plots with added spiders. This interaction effect points out that generalist predators can be effective in monocultures. I suggest that the importance of natural enemies in monocultures is often overlooked because only the initial colonization phase is being studied. By augmenting predator populations I was able to simulate densities equivalent to those in more established cropping systems. The increased herbivore densities in dicultures with added spiders might be explained by possible predation by E. ovata on other natural enemies of P. xylostella and M. configurata in dicultures but not in monocultures. Supporting evidence for this interpretation lies in the fact that percent parasitism of P. xylostella by the ichneumonid, Diadegma insulare was lower in plots with added spiders than in control plots. Furthermore, parasitism of P. xylostella by D. insulare increased with host density in diculture plots, but not in monoculture plots. Mamestra configurata was not subject to parasitism in this study, precluding assessment of a similar relationship. No A. californica larvae were found in plots with additional spiders. In contrast, P. rapae larvae were not affected by the experimental treatments. Plant size was a crucial determinant of both herbivore populations and percent parasitism of those herbivores. Most importantly, had plant size not been accounted for, the importance of vegetational diversity to both herbivore densities and percent parasitism would have been overestimated. For example, the incorrect conclusion, that vegetational diversity alone was important in determining the abundance of both of the generalist feeders would have been reached. The greater densities of A. californica in monocultures and M. configurata in dicultures were accounted for by plant size. Without plant size adjustments, percent parasitism of P. xylostella by D. insulare would have been misinterpeted as being greater in monocultures than dicultures. With plant size adjustments, the importance of E. ovata augmentations on lowering percent parasitismwas unmasked. All important interaction effects were discovered only after adjustments for plant size had been made. Despite the low densities of all herbivore species, significant responses to experimental treatments were found in three of the four species studied. Only P.l rapae was unaffected by any of the treatments. However, conclusions based on the feeding ng habits of the herbivores could not be made. The polyphagous feeders were affected by generalist predation as much as the crucifer specialist. Parasitism was found in only two of the species, P. xylostella and A. californica. Of these two species parasitism of the specialist, P. xylostella was affected by both vegetational diversity and generalist predation, whereas parasitism of A. californica was not. My study emphasizes multifaceted interactions between the size and diversity of a primary resource and several trophic levels of consumers. Multifactor models, involving several aspects of a cropping system, are required to uncover the important mechanisms behind variable herbivore responses to vegetational diversity. / Land and Food Systems, Faculty of / Graduate