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The complexity of the behaviour of neonate Eldana saccharina Walker (Lepidoptera: Pyralidae) larvae and the limited information on their response to the morphological characteristics of South African sugarcane varieties was the primary justification to study antixenotic/antibiotic effects on larval behaviour. Laboratory experiments were conducted with stalk segments in plastic jars inoculated with larvae and in a metal cage covered with gauze. In jars, the larvae were observed until they penetrated the stalks. After 14 days, the stalks were dissected and larvae weighed. In all varieties, larvae moved directly to the node after inoculation and penetrated the stalk through leaf scars and buds. No significant differences in larval mass were observed among varieties. In cage experiments different parts of the node, namely the rind below the wax band; the bud; and the root primordia were tested. There was a clear indication that rind hardness and the budscale properties are associated with varietal resistance and only affect early instars. The experiments were repeated using whole cane plants in a glasshouse. The results were similar to those of laboratory experiments. In the Insect Rearing Unit, scraped waxes from different varieties were incorporated into the diet. Larval masses from different diets showed significant differences among varieties, but they did not conform to the known resistance ratings, as cane varieties N12 and N21 showed high susceptibility, instead of resistance. Dispersal behaviour of neonates shortly after hatching was investigated in 'mobility experiments' conducted on live cane plants. Mobility is important because the more time neonates spend wandering around on the stalk surface or on exposed parts of the plant, the more vulnerable they are to predation and other adverse factors that may reduce their survival. Experiments to test stalk penetration by larvae on the node showed that neonates required a softer food source before attacking the hard nodal parts. Second and third instar larvae were used subsequently to the mortality of all neonates fed on the rind, which in turn resulted in non-significant differences, suggesting that feeding on debris and/or leaves is critical to the survival and penetration of larvae into the sugarcane stalk. Incorporation of the characteristics tested in these experiments aims to reduce the number of larvae that penetrate the stalk and to expose them for longer on the surface where their numbers may be controlled by predators and insecticides. The resistant varieties used in these experiments have high fibre and less sugar, but newer varieties, such as N29 and N33 incorporate both high resistance and high sucrose yield, which are the two key elements for optimised sugar production. Chemical characteristics of the plants need to be taken into consideration as high sucrose is seldom found in fibrous varieties. Leaf sheath tightness is another characteristic that would go well with leaf sheath hairiness, because though not tested in this work-would make it difficult for the larvae to get to the smooth adaxial surface of the leaf. The hardness of trichomes is another feature that needs to be investigated, because a variety may have dense, but soft pubescence that does not repel even the most sensitive larvae, neonates. At present, integrating plant resistance with cultural control, i.e. field hygiene etc. is cost-beneficial for the sugar industry. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2002.

The limited availability of land to forestry and the ensuing emphasis on intensive silviculture, developed a renewed interest in soil pests in the establishment of plantations. Ten field trials were planted over three seasons to determine the mortality factors influencing the establishment of commercial eucalypt and black wattle plantations in the Natal Midlands, and simultaneously, to investigate the chemical control of the soil pest component. A complex of indigenous soil pests contribute to an average 22,9 % failure of Acacia mearnsii and Eucalyptus grandis seedlings from reaching full establishment. This pest complex, which includes termites, whitegrubs, cutworms, tipulid larvae, wireworms, millipedes and nematodes, was responsible for an average 12,3 % of the failure of the plantings to establish. In the absence of termites, in shallow humic soils, whitegrubs followed by cutworms were the most frequent and economically important pests. Eucalypts are more susceptible than wattle seedlings to whitegrub damage when planted in marginal sites. Seedlings in the summer rainfall region were most susceptible to whitegrub damage from December to April; and to cutworm damage during the first two months after planting. An average of 398 hectares was annually damaged by whitegrubs and cutworms. The total annual loss in planting costs and the additional costs of blanking over the three year study period were 1,22 and 2,65 million rands respectively. Existing non-chemical control applicable to woodlot forestry is reported. Chemical control as one of the options in the management of whitegrubs and cutworms was evaluated. The controlled release formulations of carbosulfan 10% and chlorpyrifos 10% at 1,0 g active ingredient/tree (a.i./tree), gamma BRC 0,6% dust at 0,06 g a.i./tree and the synthetic pyrethroid deltamethrin 5 % SC at 0,025 g a.i./tree were persistent and effective in controlling whitegrubs, even when applied early in the planting season. Deltamethrin 5 % SC at 0,025 g a.i./tree was also successful in controlling cutworms. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1995.

False codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) is considered the most important indigenous pest of citrus in southern Africa. Major concerns such as progressive insecticidal resistance, the negative impact of insecticides on the environment, as well as the influence of consumers opposed to chemical residues on fruit, created opportunities for biological control methods such as Sterile Insect Technology (SIT). This technology is now established in the Western and Eastern Cape provinces of South Africa as an effective, sustainable alternative to conventional FCM control methods. Due to the prevalence of the pest in all citrus producing areas of South Africa, potential for SIT to expand is enormous. Success of an SIT programme is highly dependent on efficient application of the technology to achieve its objectives in a timeous manner. The aim of this study was to advance the application of SIT for control of FCM on citrus in South Africa, by investigating the effect of certain critical stages in the process. The effect of long-distance transportation on fitness of irradiated FCM was determined, showing reduced performance with cold-immobilized transport. A significant decrease in flight ability and longevity of irradiated FCM was found, although critically, realized fecundity was not affected. The effect of two different insecticides in the pyrethroid and organophosphate chemical groups were investigated for their residual effect on mortality of released irradiated FCM, to determine if these pest control programmes could be integrated. Both chlorpyrifos and tau-fluvalinate were effective in killing irradiated FCM for a number of days after application, after which degradation of the active ingredient rendered it harmless. This effect was found to be similar for irradiated and non-irradiated males, consequently ratios of sterile : wild male FCM should be retained regardless of whether sprays are applied or not. The modes for release of sterile FCM in an SIT programme were investigated. Efficacy of ground and aerial release platforms were tested by evaluating the recovery of released irradiated male FCM in these orchards. More irradiated FCM were recovered in orchards released from the ground compared to air. However, an economic analysis of both methods shows application of irradiated insects over a large geographical area is more cost-effective by air. Depending on the terrain and size of the target area, a combination of both methods is ideal for application of SIT for control of FCM in citrus. Development of application technology for advance of the programme is discussed and recommendations for future research and development are offered.

Orientador: Daniela Carvalho dos Santos / Banca: Hélio Conte / Banca: Daniela Oliveira Pinheiro / Resumo: Ceraeochrysa claveri, popularmente conhecido como bicho lixeiro, é um inseto predador de ovos e larvas de insetos pragas encontrados em diferentes ecossistemas agrícolas. O bicho lixeiro se destaca por apresentar potencial para ser utilizado em programas de Controle Biológico, uma vez que é predador na fase de larva, apresenta curto tempo de desenvolvimento, fácil criação massal e alto potencial reprodutivo na fase adulta. Com o propósito de aprofundar o conhecimento na morfologia e ultraestrutura do intestino médio de C. claveri, o objetivo deste trabalho foi caracterizar histológica e ultraestruturalmente o intestino médio de C. claveri no terceiro ínstar de larva, pupa e adulto. Objetivamos, ainda, avaliar o efeito da ingestão do óleo de nim (Azadirachta indica A. Juss) (Meliaceae) sobre as células epiteliais do intestino médio de larva de terceiro ínstar, pupa e adulto de C. claveri. Ovos de Diatraea saccharalis foram tratados com óleo de nim em três diferentes concentrações (0,5; 1 e 2%) e oferecidos como alimento a larvas de C. claveri durante todo período larval. Após coleta e fixação do intestino médio de larva, pupa e adulto (grupos controle e tratados com óleo de nim), as regiões do mesêntero (anterior, média e posterior) foram processadas para análise histológica (citoquímica e imunocitoquímica) e para análise ultraestrutural. Nossos resultados mostraram que o intestino médio de C. claveri, para as três fases do ciclo de vida, é do tipo pseudoestratificado, composto por células colunares, regenerativas e endócrinas; diferenças morfológicas e ultraestruturais no epitélio permitem caracterizar duas regiões, anterior e posterior, atuando respectivamente na secreção e absorção; região média apresenta características... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Ceraeochrysa claveri, popularly known as trash-carriers is a predator insect of eggs and larvae of insect pests found in different agroecosystems. The trash-carriers stands out because it has the potential to be used in biological control programs, once it is a predator in the larval stage; it has short developmental times, easy mass-rearing and high reproductive potential in adult stage. In order to deepen the knowledge on the morphology and ultrastructure of the midgut of C. claveri, the aim of this study was to characterize histological and ultrastructurally the midgut of C. claveri in the third instar larva, pupa and adult. We also evaluate the effect of ingestion of neem oil (Azadirachta indica A. Juss) (Meliaceae) on the midgut epithelial cells of third instar larva, pupa and adult of C. claveri. Diatraea saccharalis eggs were treated with neem oil at three different concentrations (0.5, 1 and 2%) and provided as food to larvae of C. claveri throughout the larval period. After collected and fixed the midgut of larva, pupa and adult (control and treated groups with neem oil), the midgut regions (anterior, middle and posterior) were processed for histological (cytochemistry and immunocytochemistry) and for ultrastructural analysis. Our results showed that the midgut of C. claveri for the three phases of the life cycle is of pseudostratified type, consisting of columnar cells, regenerative cells, and endocrine cells, morphological and ultrastructural differences in the epithelium allowed to characterize two regions, the anterior and posterior, they working mainly in the secretion and absorption respectively; the middle region has intermediate characteristics, and it is considered a transitional area. The ingestion of neem oil in the larval stage of C. claveri showed to be toxic to this predator, causing ultrastructural alterations... (Complete abstract click electronic access below) / Mestre

Made available in DSpace on 2014-06-11T19:30:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-24Bitstream added on 2014-06-13T18:59:57Z : No. of bitstreams: 1 scudeler_el_me_botib.pdf: 6021367 bytes, checksum: 931a3db0cfc7da410cba6a737f5365bf (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Ceraeochrysa claveri, popularmente conhecido como bicho lixeiro, é um inseto predador de ovos e larvas de insetos pragas encontrados em diferentes ecossistemas agrícolas. O bicho lixeiro se destaca por apresentar potencial para ser utilizado em programas de Controle Biológico, uma vez que é predador na fase de larva, apresenta curto tempo de desenvolvimento, fácil criação massal e alto potencial reprodutivo na fase adulta. Com o propósito de aprofundar o conhecimento na morfologia e ultraestrutura do intestino médio de C. claveri, o objetivo deste trabalho foi caracterizar histológica e ultraestruturalmente o intestino médio de C. claveri no terceiro ínstar de larva, pupa e adulto. Objetivamos, ainda, avaliar o efeito da ingestão do óleo de nim (Azadirachta indica A. Juss) (Meliaceae) sobre as células epiteliais do intestino médio de larva de terceiro ínstar, pupa e adulto de C. claveri. Ovos de Diatraea saccharalis foram tratados com óleo de nim em três diferentes concentrações (0,5; 1 e 2%) e oferecidos como alimento a larvas de C. claveri durante todo período larval. Após coleta e fixação do intestino médio de larva, pupa e adulto (grupos controle e tratados com óleo de nim), as regiões do mesêntero (anterior, média e posterior) foram processadas para análise histológica (citoquímica e imunocitoquímica) e para análise ultraestrutural. Nossos resultados mostraram que o intestino médio de C. claveri, para as três fases do ciclo de vida, é do tipo pseudoestratificado, composto por células colunares, regenerativas e endócrinas; diferenças morfológicas e ultraestruturais no epitélio permitem caracterizar duas regiões, anterior e posterior, atuando respectivamente na secreção e absorção; região média apresenta características... / Ceraeochrysa claveri, popularly known as trash-carriers is a predator insect of eggs and larvae of insect pests found in different agroecosystems. The trash-carriers stands out because it has the potential to be used in biological control programs, once it is a predator in the larval stage; it has short developmental times, easy mass-rearing and high reproductive potential in adult stage. In order to deepen the knowledge on the morphology and ultrastructure of the midgut of C. claveri, the aim of this study was to characterize histological and ultrastructurally the midgut of C. claveri in the third instar larva, pupa and adult. We also evaluate the effect of ingestion of neem oil (Azadirachta indica A. Juss) (Meliaceae) on the midgut epithelial cells of third instar larva, pupa and adult of C. claveri. Diatraea saccharalis eggs were treated with neem oil at three different concentrations (0.5, 1 and 2%) and provided as food to larvae of C. claveri throughout the larval period. After collected and fixed the midgut of larva, pupa and adult (control and treated groups with neem oil), the midgut regions (anterior, middle and posterior) were processed for histological (cytochemistry and immunocytochemistry) and for ultrastructural analysis. Our results showed that the midgut of C. claveri for the three phases of the life cycle is of pseudostratified type, consisting of columnar cells, regenerative cells, and endocrine cells, morphological and ultrastructural differences in the epithelium allowed to characterize two regions, the anterior and posterior, they working mainly in the secretion and absorption respectively; the middle region has intermediate characteristics, and it is considered a transitional area. The ingestion of neem oil in the larval stage of C. claveri showed to be toxic to this predator, causing ultrastructural alterations... (Complete abstract click electronic access below)

The false codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), is an important pest of citrus in South Africa and challenging to manage due to its inconspicuous nature. An effective method currently being employed for the area-wide suppression of the FCM is the Sterile Insect Technique (SIT) and the effective dispersal of sterile moths is very important for success with SIT. This study was conducted in the Addo area of the Sundays River Valley (Eastern Cape) where the programme is commercially used. In this study, sterile male moths were released in different orchards on a citrus farm, and in nearby veld at different times of the year, and their dispersal was monitored through the use of pheromone traps. Various climatic factors were monitored. This provided insight into the local dispersal of sterile male FCM adults in response to abiotic cues (particularly climatic factors). The movement of the FCM in four citrus cultivars, namely lemons, navel and Valencia oranges and mandarins and in the nearby veld (open field), was determined at six different stages of the year. Results clearly indicated that sterile FCM movement is concentrated within citrus orchards, as very few moths were trapped beyond 30 m from the release point, particularly in navel and Valencia orchards. Of the climatic factors measured, minimum and maximum temperatures had the most significant influence on FCM dispersal, and based on the results, various recommendations are made for the releases of sterile FCM in an area-wide SIT management programmes on citrus. A better understanding of the dispersal capabilities of the FCM in an agricultural system, under different conditions and at different times of the year, is invaluable not only in improving release strategies in an SIT programme but in planning future control strategies against the FCM.

Petrol and ethanolic extracts of six asteraceous weeds were added to artificial diet and screened for inhibition of larval growth on variegated cutworm, Peridroma saucia (Hbn.). Petrol and ethanolic extracts of Artemisia tridentata and Chamomilla suaveolens and ethanolic extracts of Chrysothamnus nauseosus and Centaurea diffusa were highly inhibitory at five times the naturally occurring concentrations. The two C. suaveolens extracts and the ethanol extract of A. tridentata were active at the natural concentration (100%) and were further examined at 20, 40, 60, and 80% of this level. Inhibition of larval growth was directly related to concentration for each of the three extracts tested. EC₅₀'S (effective concentration to inhibit growth by 50% relative to controls) for the three extracts were 36-42% of the naturally occurring level in the plants. Nutritional indices were calculated for second instar P. saucia feeding on the active ethanolic A. tridentata extract and the petrol extract from C. suaveolens. The relative growth rate (RGR) of P. saucia larvae fed the ethanolic extract of A. tridentata in artificial diet was significantly lower than that in larvae fed diet with the petrol extract of C. suaveolens and larvae on control diet. Dietary utilization was significantly lower for larvae fed the A. tridentata extract. Results of a field trial indicated that a single treatment of A. tridentata extract at the equivalent of 0.2 g/ml could protect cabbage significantly better than the carrier solvent (30% aq ethanol) or distilled water as measured by a visual damage estimate. An insecticide standard, deltamethrin (17.9 µg/1 with 0.4% Superspred TM ), suppressed pest damage significantly better than the A. tridentata-extract treatment. A residual oviposition deterrency to Pieris rapae was found in the field results. Caged experiments in the laboratory confirmed the contact oviposition deterrency of the A. tridentata extract at 0.2 g/ml. Offspring of field-collected P. saucia larvae grew 2.5-fold heavier than larvae from the laboratory colony. However, diet with the A. tridentata extract inhibited both field-collected and laboratory reared saucia larvae equally when compared to their respective controls fed untreated diet. In summary, these results indicate the potential benefit of using specific unrefined plant extracts for growth inhibitors and oviposition deterrents against insect pests. The contribution of individual phytochemicals in the A. tridentata ethanolic extract to growth inhibition or oviposition deterrency is currently speculative. / Land and Food Systems, Faculty of / Graduate

Studies were conducted on the penetration and permanence of 1.0% chlorpyrifos [0,0-diethyl 0-(3,5,6-trichloro-2-pyridyl) phosphorothioate], formulated as Dursban® TC (Dow Chemical Co.), in pine (Pinus spp.), spruce (Picea spp.), and fir (Abies spp.). Results indicated the highest degree of penetration in southern yellow pine. Surface roughness and orientation had an effect upon chemical penetration. Longevity studies ranging over time periods from three to 52 months revealed rapid loss of chlorpyrifos from the surface of the wood but relatively stable below-surface concentrations. Similar studies with 0.5% permethrin [(3-phenoxypheny]) methyl] (+) - cis, trans-3-(2,2-dichloroethenyl)-2,2dimethylcyclopropane-carboxylate] applied to the same wood types revealed comparable penetration differentials between types of wood. Formulation differences had little significant effect on penetration. One-year longevity studies revealed surface losses less drastic than those reported for chlorpyrifos, as well as superior below-surface stability. Studies employing volumes five, 10, and 25 times less than that required to achieve a runoff application revealed significantly lower chlorpyrifos penetration with reduced volume. Some reduced volumes resulted in below-surface concentrations of chlorpyrifos higher than the LC₉₀ value for Hylotrupes bajulus (Coleoptera: Cerambycidae). Toxicity testing with chlorpyrifos on first-instar larvae of H. bajulus, the old house borer, revealed contact LC₅₀ and LC₉₀ values of 14 ppm and 78 ppm, respectively. Similar tests with permethrin indicated LC₅₀ and LC₉₀ values of 2 ppm and 8 ppm. Tests with first-instar larvae on wood treated with 1.0% chlorpyrifos and 0.5% permethrin resulted in 100% mortality on wood aged for nine months in the case of chlorpyrifos, and six months in the case of permethrin. Tests utilizing H. bajulus eggs placed on treated wood revealed ovicidal properties of permethrin and lack of ovicidal effect with chlorpyrifos. Accelerated ageing studies employing an environmental chamber (40°C, 70% RH) at a 1:6 ratio of accelerated to natural weathering indicated no significant difference in surface or below-surface concentrations of permethrin in wood aged artificially for one month and in wood aged naturally for six months. Similar results were obtained with chlorpyrifos-treated wood artificially aged for 10 months and aged naturally for 4-1/3 years. Mathematical models were developed to predict surface and one millimeter concentrations of chlorpyrifos and permethrin after five and 10 years. / Ph. D.