Thesis (M. Sc. (Zoology and Entomology))--Rhodes University, 2006.

No description available.

The objectives of this study were 1) to further clarify the status of the genera Polydrusus and Scythropus and 2) to redescribe and elucidate the morphology and distribution of the species of Scythropus in order to better facilitate their identification. Some 1650 specimens were used in the study and about 300 of these were critically examined for morphological variations of the head, beak, antennae, thorax, elytra, abdomen, integument, legs, genitalia, and eighth tergite and ninth segment of the male. Over one hundred genitalia were dissected and critically examined for good characters. The male genitalia were the most reliable single characters used in separating the species, however, other characters such as variations in antennae, color, vestiture, elytral patterns, integument color, and features of the head and legs were used to describe and further isolate them. A key has been constructed to facilitate more accurate identification of the species of Scythropus, and the distribution is given as well as the host plants when known. Seventy illustrations were made of the male genitalia, abdomen, pronotum, antenna, elytral vestiture, and the eighth tergite and the ninth segment of the males.

Factors associated with feeding injury to grass plants by two species of adult billbugs, Sphenophorus gentilis and S. parvulus, were evaluated. Early season tests utilized adult bluegrass billbugs while later studies involved wildrye billbugs. Types of feeding injury were determined and preferred feeding locations on host plants were identified for each billbug species. Greenhouse and field studies compared different species of grasses, individual plants within a species, and plants from different locations, for billbug susceptibility. The effect of grass plant age and stem size were also tested using bluegrass billbugs. Using analysis of variance and multiple comparison tests, significant differences in amounts of feeding injury were determined among entries. Wildrye plants from different geographic locations showed large differences in susceptibility to wildrye billbug feeding when compared in a greenhouse study. Grass stem size had an effect on amounts of feeding injury incurred to 2 out of 3 wheatgrasses by bluegrass billbugs. A field study suggested that host plant age was not a factor in susceptibility of slender wheatgrass to bluegrass bfllbugs. Implications for screening grasses for resistance to billbugs using adult insects are discussed. Comparisons between greenhouse and field studies are also examined.

A biological and integrated control program for Carduus thistles was developed using the biological control agents Rhinocyllus conicus Froelich and Ceuthorhynchidius horridus (Panzer) and the herbicide 2,4-Dichlorophenoxyacetic acid (2,4-D). Field studies on the development of Ceuthorhynchidius horridus (Panzer) on Carduus thistles in Virginia between 1975-1978 showed that the weevil has one generation annually. Oviposition occurred from mid-December until early April, and larvae occurred in rosettes from late December through late May. Teneral adults, which appeared in mid-May through June, underwent an aestival diapause during most of July through September. Adult reappearance in late September coincided with an increase in feeding. Although adult feeding marks, teneral adults and first and third instar larvae were easily found in the field, detection of eggs, second instars or overwintering adults was difficult and time consuming. Acute and chronic effects of spring application of 2,4-D (LVA) on adult C. horridus were examined. LC₅₀ values for males (70.2 kg/ha) and females (61.4 kg/ha) corresponded to 41.7 and 36.6 times, respectively, the recommended application rate of 1.68 kg/ha. Treatment with 1.68 kg/ha did not affect adult survival, but increased dosages (16.8-147.8 kg/ha) caused significantly greater mortality. Adult vitality, measured by number of feeding marks/weevil and weight change/time, was unaffected by the herbicide. Field application of herbicides did not prevent survival, reproduction, or population increase of C. horridus. Herbicidal effect on larval R. conicus was studied by examining the mortality, emergence rates and weights of weevils developing from plants treated with 2,4-D (LVA). Infested heads, obtained by caging ovipositing R. conicus on primary heads of musk thistle (Carduus nutans L.) (resembles C. thoermeri Weinmann), were treated with 2,4-D at 1.68 kg/ha 0-3 weeks after oviposition. Blooms treated immediately following oviposition failed to support larval development beyond the second instar. Developmental times and weights of weevils that emerged from blooms sprayed at 1, 2, and 3 weeks were not significantly different from controls. Plants sprayed up to 2 weeks after oviposition (late-bud to early-bloom) did not produce viable seeds. Treatments at 3 weeks after oviposition (full-bloom) allowed 10% germination of seeds not damaged by R. conicus in primary heads, and plants survived to produce additional heads. Acute and chronic effects of the herbicide 2,4-D on adult R. conicus were also examined. LC₅₀ values for adults prior to over-wintering (males 78.6 kg/ha; females 61.0 kg/ha) were lower than those for overwintered weevils (males 117.1 kg/ha; females 126.6 kg/ha), but were still at least 40 times the recommended application rate of 1.68 kg/ha. Survival was not significantly affected by direct application of 2,4-D at 1.68 kg/ha plus sticker or by exposure to herbicide sprays and residue while on musk thistle rosettes. Mean egg production/ovipositing female/3 day period was not significantly different (range = 5.44 - 7.60), regardless of the 2,4-D dosage applied (range = 0.0 - 147.84 kg/ha); all ovipositing weevils produced viable eggs. Field treatment with up to 2.24 kg/ha of 2,4-D resulted in death of host plants, but did not prevent survival or reproduction of R. conicus populations. / Ph. D.

As respostas comportamentais do bicudo-do-algodoeiro aos compostos orgânicos voláteis de plantas em fase vegetativa, plantas com botão floral, botão floral, flor e maçã e plantas em floração do algodoeiro, e a presença dos semioquímicos que responsáveis pela interação inseto-planta foram investigadas neste trabalho. Todos os experimentos foram realizados em condições de laboratório usando insetos criados em dieta artificial e planta cultivadas em casa de vegetação. Bioensaios usando olfatômetro em ípsilon demonstraram que macho são atraídos pelos voláteis das plantas em fase vegetativa e flores, e as fêmeas pelos voláteis das flores e plantas em floração. Ambos os sexos do bicudo-do-algodoeiro não foram traídos pelos voláteis de planta com botão floral, botão flora e maçã. Compostos voláteis destes tratamentos foram coletados por oito horas e analisados por GC-MS, revelando 13 compostos liberados pelas plantas em floração e 11 nas flores e plantas em fase vegetativa. As plantas em sus respectivas fases de desenvolvimento liberam maiores quantidades de compostos que as flores. As antenas de machos e fêmeas foram eletrofisiologicamente responsivas aos extratos voláteis destes tratamentos, confirmando o mesmo padrão de resposta observado nos bioensaios de olfatometria. Os compostos sintéticos β-caryophyllene e cis-3-hexenyl-acetate presentes em maiores quantidades em plantas em floração não foram atrativos para as fêmeas na concentração utilizada nos bioensaios de olfatometria. Os resultados encontrados neste trabalho demonstram que machos e fêmeas exploram os compostos orgânicos voláteis liberados pelas diferentes fases desenvolvimento da planta e pelas flores, aportando assim, com novas evidencias sobre a interação entre A. grandis e seu principal hospedeiro, G. hirsutum, abrindo a possibilidade de realizar novos estudos visando a aplicabilidade de estes semioquímicos no monitoramento e controle deste importante inseto-praga. / The behavioral responses of the cotton boll weevil to the volatile organic compounds of plants in the vegetative stage, plants with square, squares, flower, boll and flowering plants of cotton, and the presence of semiochemicals responsible for the insect-plant interaction were investigated in this work. All experiments were carried out in laboratory conditions using insects raised in artificial diet and plant grown under greenhouse conditions. Y-tube olfactometer bioassays showed that male were attracted by volatiles of plants in vegetative phase and flowers, and the females by flowers and flowering plants volatiles. Both sexes of the cotton boll weevil were not attracted by plant with squares, squares and boll volatiles. Volatile compounds of these treatments were collected for eight hours and analyzed by GC-MS, revealing 13 compounds released by flowering plants and 11 by flowers and plants in the vegetative stage. Plants in their respective stages of development release larger amounts of compounds than flowers. Male and female antennae were electrophysiologically responsive to the volatile extracts of these treatments, confirming the same response pattern observed in the olfactory bioassays. The synthetic compounds β-caryophyllene and cis-3-hexenyl-acetate present in larger quantities at flowering plants were not attractive for females at the concentration used in Y-tube olfactometer bioassays. The results obtained in this work demonstrate that males and females exploit the volatile organic compounds released by cotton plant at different development stages and by the flowers, thus contributing with new evidence about the interaction between A. grandis and their major host plant, G. hirsutum, which will serve as support for studies aiming at the applicability of these semiochemicals in the monitoring and control of the cotton boll weevil.

Eugenia uniflora L. (pitangueira) is a native fruit species in Brazil, with wide geographical distribution, has economic potential because its fruit marketed, can be recommended for planting in heterogeneous reforestation for the recovery of degraded areas and permanent preservation to be attractive to wildlife. The present study aimed to identify the species of insects associated with seed, assess the damage caused by insect predators, its consequences on viability and occurrence of fungi on seeds of Eugenia uniflora. The samples were collected in FEPAGRO located in Santa Maria, RS. The seeds were evaluated for the occurrence of posture, punching, number of insects per seed (conditioned in individual containers), percentage of predation and substrate consumption. Moreover, germination test was performed to evaluate the influence of predation on seed viability, the occurrence of insects that occasion and identification of fungal genera that occur in the seeds. Emerged from seeds two species of insects, Atractomerus pitangae (Marshall, 1925) (Coleoptera:Curculionidae) and a new species of Paracrias sp. nov. (Hymenoptera:Eulophidae), parasitoid larvae of Curculionidae. Atractomerus pitangae and Paracrias sp. nov. are found associated with the seeds of Eugenia uniflora. The occurrence of A. pitangae tends to increase at advanced stages of maturation. The insects cause damage to seeds that attack, but the number of predated seeds is not expressive. There is a decrease in the percentage of normal seedlings as the frequency rises insects. The presence of insects is higher at the end of the fruiting period. The insects have a higher occurrence in the advanced stages of maturation. The most common fungal genera are Penicillium sp., Fusarium sp., Alternaria sp. and Aspergillus sp. and vary depending on fruit maturation. / Eugenia uniflora L. (pitangueira) é uma espécie frutífera nativa do Brasil, com ampla distribuição geográfica, apresenta potencial econômico, pois sua fruta é comercializada, pode ser recomendada para plantio em reflorestamentos heterogêneos destinados à recomposição de áreas degradadas e de preservação permanente por ser atrativa para a fauna. O presente estudo teve como objetivo, identificar as espécies de insetos associadas às sementes, avaliar os danos causados por insetos predadores, suas conseqüências na viabilidade e ocorrência de fungos em sementes de Eugenia uniflora. As coletas foram efetuadas na FEPAGRO localizada no município de Santa Maria, RS. As sementes foram avaliadas quanto à ocorrência de postura, perfuração, número de insetos por semente (acondicionadas em recipientes individualmente), porcentagem de predação e consumo de substrato. Além disso, foi realizado teste de germinação avaliando-se a influência da predação na viabilidade das sementes, a ocorrência de insetos nessa ocasião e a identificação dos gêneros fúngicos que ocorrem nas sementes. Emergiram das sementes duas espécies de insetos, Atractomerus pitangae (Marshall, 1925) (Coleoptera: Curculionidae) e uma nova espécie de Paracrias sp. nov. (Hymenoptera: Eulophidae), parasitóide de larvas de Curculionidae. Atractomerus pitangae e Paracrias sp. nov. são encontrados associados as sementes de Eugenia uniflora. A ocorrência de A. pitangae tende a aumentar em estágios mais avançados de maturação. Os insetos causam danos às sementes que atacam, porém o número de sementes predadas não é expressivo. Ocorre uma redução na porcentagem de plântulas normais à medida que a frequência de insetos aumenta. A presença de insetos é maior no final do período de frutificação. Os insetos apresentam maior ocorrência nos estágios de maturação mais avançados. Os gêneros fúngicos mais frequentes são Penicillium sp., Fusarium sp., Alternaria sp. e Aspergillus sp., e variam em função da maturação dos frutos.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The objective of this study was to evaluate the population fluctuation and the distribution of the soybean root weevils (Coleoptera: Curculionidae), and the population fluctuation was determined in a soybean area in the period December, 2006 to November, 2007, in the Restinga Seca county, RS. Distribution in space and time was evaluated in a soybean experimental area in 2006-2007 at UFSM. Twenty trenches with a dimension of 0.25 m2/unit were made every two weeks for evaluation of larvae and pupae population fluctuation and 105 trenches with the same dimension were made to determine larvae distribution. To evaluate population of adults, ten emergency cages of 2.00 m2/unit were used. Adults distribution was evaluated weekly with four cloth stroke in each of the 105 sampling points of the soybean area. Larvae were found almost during the 12 months period of evaluation. They were scarce from October to November, 2007, however, predominate medium and large sizes (3rd and 5th instars, respectively). 74 % of the larvae population found concentrated in the first 0. 10 m of depth in the soil. A population peak was observed in February 2007, with a population of 16 larvae/m2 including mainly 1st and 2nd instars. Only naupactini belonging to the species Naupactus purpureoviolasceus were collected in the cages for adults. A typical aggregated distribution for a soil insect was observed in this study. Pupae phase was observed as temperature raise in early spring and last about four weeks. Adults emerged in spring and summer, with higher populations from October to January. Adults of soybean root weevils were initially located at the edge of the soybean field, but they had an aggregated distribution from the first point of occurrence. The genera Naupactus e Pantomorus were predominant in the soybean area of Santa Maria, with six species being identified in this study. Adults sampling is recommended as a tool to predict the occurrence of larvae in the coming soybean season. / O objetivo do trabalho foi estudar os aspectos biológicos dos curculionídeos-das-raízes e identificar as espécies ocorrentes na cultura da soja, sendo que o estudo da flutuação populacional dos curculionídeos-das-raízes (Coleoptera: Curculionidae) foi realizado no município de Restinga Seca, RS, em área de cultivo de soja, no período de 12/2006 a 11/2007. Para a avaliação da distribuição espaço-temporal o trabalho foi realizado em Santa Maria, RS, em área experimental da UFSM em 2006-2007. Para avaliar a flutuação populacional de larvas e pupas foram realizadas trincheiras, (20 quinzenais) com a dimensão de 0,25 m2/unidade. Para avaliar a distribuição de larvas, foram realizadas 105 trincheiras, com a mesma dimensão. Para o levantamento de adultos, utilizaram-se 10 gaiolas de emergência com dimensão de 2m2/unidade, enquanto para avaliar a distribuição destes foram realizadas quatro batidas de pano por ponto de amostragem (105 pontos), avaliados semanalmente. Entre 10 e 11/2007, o número de larvas encontradas na área foi reduzido, porém predominaram larvas médias e grandes (3°e 5° instares). A população de larvas camada de zero a 0,10 m, totalizou 74%. O pico populacional ocorreu em fevereiro, com a população de 16 larvas/m2 com predominância de larvas de 1° e 2° ínstares. Foram encontradas larvas dos curculionídeos-das-raízes em praticamente os 12 meses de avaliação. Nas gaiolas, foram coletados somente naupactini pertencentes à espécie Naupactus purpureoviolasceus. Em relação distribuição destes insetos-praga observou-se que ocorrem de maneira agregada, que é comportamento típico de praga de solo. A fase de pupa ocorreu no início da primavera, quando as temperaturas tornaram-se mais elevadas, com duração aproximada de quatro semanas. Os adultos dos curculionídeos-das-raízes emergiram no verão e final da primavera, com picos populacionais entre outubro e janeiro. A população de adultos dos curculionídeos-das-raízes se distribuiu de forma agregada desde o primeiro foco de ocorrência, e inicialmente se concentraram nas bordas da lavoura. Os gêneros Naupactus e Pantomorus predominam em área de soja em Santa Maria, e foram identificadas seis espécies destes gêneros. Desse modo, a amostragem de adultos é recomendada para que o produtor possa prevenir-se de ocorrência de larvas na safra posterior.

Water lettuce, Pistia stratiotes Lamarck (Araceae) is a South American plant that has the potential to be a very damaging and important aquatic weed in many tropical countries, including South Africa. It has the potential to rapidly multiply vegetatively and completely cover watercourses in a very short space of time outside of its natural range under ideal conditions and without its natural enemies. In such instances, the weed may cause hindrances to water transport and fishing, increasing chances of malaria, as well as affecting the natural ecology of the system. Water lettuce can also set seed, which may lay dormant for long periods, germinating when conditions are favourable. It is therefore very necessary to adopt control methods against the weed where it is a problem. However, water lettuce has also been effectively and completely controlled in many countries by the leaf-feeding weevil, Neohydronomus affinis Hustache. High nutrient levels in the form of nitrates and phosphates have been shown to have largely negative effects on biological control in several studies, with control being incomplete or taking longer than in similar areas with lower nutrient levels. The effectiveness of N. affinis on the biological control of water lettuce was investigated in a laboratory study, growing P. stratiotes plants with and without insects at different nutrient concentrations. In these studies biological control of water lettuce with N. affinis was found to be complete under eutrophic nutrient conditions, although control took longer when higher nutrient levels were tested. A field site study was conducted at a sewage settlement pond in Cape Recife Nature Reserve near Port Elizabeth, South Africa. This highly eutrophic system was used as a field example for the effectiveness of biocontrol of P. stratiotes by N. affinis under eutrophic conditions. The weevils at Cape Recife caused a massive and rapid crash in the percentage coverage of the weed, from 100% in May 2003, to approximately 0.5 % in September 2003. Plant growth parameters were also found to decrease considerably in size correspondingly with this crash from May 2003 until spring 2003. Plant size only again started to increase gradually but steadily through spring 2003 and into summer. In the laboratory studies, the fecundity of weevils was shown to be much higher on plants grown under higher nutrient concentrations than on plants grown in lower nutrient concentrations. The results from the wing-muscle analysis under different nutrient concentrations were not easy to interpret, and there were few differences in wing muscle state between most of the concentrations. From these findings it is suggested that nutrient concentration, particularly high levels of nitrates and phosphates is not a limiting factor in terms of effective biological control of P. stratiotes with N. affinis, but that under high nutrient conditions biological control might take longer.

In South Africa the genus, Eucalyptus plays an important role as a major economic component in the forest and mining sector. Unfortunately, this genus has problems due to damage by pests. The Eucalyptus snout beetle, Gonipterus scutellatus, feeds and defoliates the leaves of eucalypts. Plants produce secondary metabolites, which protects them against defoliation by insects and herbivores. This study focuses on the variations of total soluble phenolic content of nine Eucalyptus species between the species and within the species throughout the year. Total soluble phenols were quantified with the Folin-Ciocalteau reagent. There was a general increase in the concentration of total soluble phenols throughout the year. The content of total soluble phenols were generally higher compared to carbohydrates. This experiment needs to be done on a continuous basis so as to formulate a screening method for eucalypt species that are resistant to G. scutellatus. / Dissertation (M Inst Agrar (Sustainable Insect Management))--University of Pretoria, 2005. / Zoology and Entomology / unrestricted