The population dynamics of the cabbage aphid (Brevicoryne brassicae) were studied on Maris Kestrel kale during the summer months, in Vancouver British Columbia, Canada. The object was to describe the temporal variation in numbers, age distribution, and quality of B. brassicae in terms of quantitative relationships between the aphid and its biotic and abiotic environment, using a simulation model. A technique was developed whereby aphid fecundity and developmental time could be estimated for aphids within the population. Aphid fecundity and rate of development decreased continuously through the season, probably in response to changes in plant quality. The plant rarely posed an upper limit on aphid increase, but populations consistently showed an initial maximal rate of increase followed by a leveling off, and eventual population decline in the autumn. Evidence presented, suggests that syrphid predation was largely responsible for the major mid-season shifts in the rate of increase of the aphid. Thompson's (1924) 'random search' model did not adequately represent syrphid predation, and further detailed studies are required. Decreasing aphid developmental and reproductive rates, production of oviparae, predation, and leaf fall, were probably responsible for population declines in the autumn. The cabbage aphid system is compared with that described by Hughes (l963) and Hughes & Gilbert (1968). The problems of generality and biological control are discussed. / Land and Food Systems, Faculty of / Graduate

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No. of bitstreams: 2 Dissertação_Sheila Avila.pdf: 1444685 bytes, checksum: 5af742f17f8020ce9558feb7331065cc (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-08-31 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Pesquisar adubações orgânicas que almejam o equilíbrio trofobiótico na cultura de interesse é de extrema importância na busca de sistemas de produção de alimentos mais sustentáveis. Com esta premissa objetivou-se no trabalho analisar a influência de diferentes adubações orgânicas sobre a preferência alimentar de Brevicoryne brassicae em Brassica oleracea var. acephala, estabelecendo inter-relações entre o metabolismo vegetal da couve, as fontes de adubação testadas e a resistência e/ou suscetibilidade aos afídeos. Para tanto, foi feito o cultivo da hospedeira em casa de vegetação, onde a mesma foi cultivada em vasos com adubação orgânica acrescentada ou não de fitoprotetores, obedecendo aos seguintes tratamentos: T1) substrato orgânico comercial a 70% + 30% de húmus (SO+H) como controle; T2) (SO+H) + biofertilizante Vairo via solo; T3) (SO+H) + biofertilizante Supermagro via solo T4) (SO+H) + urina de vaca via solo; T5) (SO+H) + Húmus líquido pulverizado; T6) (SO+H) + soro de leite pulverizado e, T7) (SO+H) + biodinâmico pulverizado. O delineamento experimental foi inteiramente casualizado com 10 repetições, sendo cada repetição (parcela) uma planta. Para os bioensaios de preferência alimentar de múltipla escolha em laboratório foi feita a criação do afídeo, sendo as avaliações realizadas as 24 e 48 horas através da contagem de indivíduos em todas as folhas (halos) representando todos os tratamentos. Também foi feito análise química dos substratos e das couves, além dos fitoconstituintes das mesmas após receber os diferentes tratamentos. Os dados foram submetidos ao teste de hipótese de KruskalWallis (p<0,05), com comparação de grupos pelo método de Simes-Hochberg, sendo após, submetidos à análise de componentes principais. A aplicação dos tratamentos influenciou na preferência alimentar de B. brassicae em B. oleracea var. acephala. Estes forneceram diferentes fontes de nutrientes ao substrato e à planta hospedeira, afetando assim, seu metabolismo vegetal e conseqüentemente a resistência e/ou suscetibilidade aos afídeos. As plantas tratadas com húmus líquido e Vairo apresentaram menor preferência pelos pulgões. Estes induziram a resistência, envolvendo o acúmulo de ácido ascórbico que se correlacionou ao manganês. Os tratamentos urina de vaca, Supermagro e em menor grau o soro de leite foram os que apresentaram folhas com maior preferência pelos afídeos, sendo estes ricos em nitratos e açúcares solúveis, estando estes compostos relacionados respectivamente aos nutrientes nitrogênio, ferro e cálcio. Já os tratamentos controle e biodinâmico apresentaram resultados intermediários de preferência e de correlação aos nutrientes e fitoquímicos. / To search for organic fertilizers that target the trophobiotic balance in the culture of interest and of extreme importance in the search for more sustainable food production systems. The objective of this work was to analyze the influence of different organic fertilizers on the Brevicoryne brassicae food preference in Brassica oleracea var. acephala, establishing interrelations between the vegetable metabolism of the cabbage, the sources of fertilization tested and the resistance and / or susceptibility to the aphids. For this, the host was cultivated in a greenhouse, where it was cultivated in pots with organic fertilization added or not of phytoprotectants, following the following treatments: T1) commercial organic substrate at 70% + 30% humus (SO + H) as control; T2) (SO + H) + biofertilizer Vairo via soil; T3) (SO + H) + biofertilizer Supermagro via soil T4) (SO + H) + cow urine via soil; T5) (SO + H) + pulverized liquid humus; T6) (SO + H) + powdered whey and, T7) (SO + H) + pulverized biodynamic. The experimental design was completely randomized with 10 replicates, each replicate (plot) being one plant. For the bioassays of multiple choice food preference in the laboratory was created the aphid, and the evaluations were performed at 24 and 48 hours by counting individuals on all leaves (halos) representing all treatments. Chemical analysis of the substrates and cabbage was carried out, besides the phyto-constituents of the same ones after receiving the different treatments. The data were submitted to the Kruskal-Wallis hypothesis test (p <0.05), with a comparison of groups by the Simes-Hochberg method, after which they were submitted to principal components analysis. The application of the treatments influenced the food preference of B. brassicae in B. oleracea var. acephala. These provided different nutrient sources to the substrate and host plant, thus affecting its plant metabolism and consequently the resistance and/or susceptibility to aphids. Plants treated with liquid humus and Vairo showed less preference for aphids. These induced resistance, involving the accumulation of ascorbic acid that correlated with manganese. The treatments of cow urine, Supermagro and, to a lesser extent, whey were the ones that presented leaves with a higher preference for aphids, being these rich in nitrates and soluble sugars, these compounds being related respectively to nutrients nitrogen, iron and calcium. The control and biodynamic treatments presented intermediate results of preference and of correlation to nutrients and phytochemicals.

PhD (Agric) (Plant Production) / Department of Plant Production / Brassicas are important vegetable crops grown for home consumption and market gardening in eastern and southern Africa. However, productivity is affected by aphids, through both direct feeding and disease transmission. Botanical insecticides have potential to control the aphids, but so far few plants have been evaluated for use on brassicas. This study was conducted to evaluate the effectiveness of Solanum panduriforme to control aphids on brassicas. Botanical extracts from three parts of S. panduriforme were assessed for their insecticidal effects on the cabbage aphid, Brevicoryne brassicae. The extracts from leaf powder (LP), ripe berry powder (BP), fresh ripe berries (RB) and fresh unripe berries (UB) were extracted with four solvents; water, ethanol, hexane and diethyl ether, using homogenisation, maceration and solvent-assisted / sequential extraction methods. The effectiveness of the extracts was determined by laboratory bioassays as well as by plant assays in the screen house and under field conditions. The experiments were replicated three or four times depending on the assays and the design used was completely randomized design (CRD). The immature (LP and UB) plant parts were generally more effective than the mature (BP and RB) plant parts, with mortalities ranging from 100 % down to 40 % respectively depending on assays. Ethanol extracts were more effective than aqueous extracts (LP 96% and 63%; BP 96% and 64%; RB 100% and 64%; UB 100% and 90%). The dried crude extracts from hexane were more effective than di-ethyl ether extracts. The group chemical analysis indicated presence of alkaloids in the berries (BP, RB and UB), which were absent in the leaves (LP). Phenolic compounds and flavonoids were present in all the extracts (LP, BP, RB, and UB). Saponins were present in the fresh parts (RB and UB). The results show how the locally available S. panduriforme plants can be used as an aphicide to control aphids on brassicas. Farmers can directly prepare an easy and cheap botanical / NRF