A dissertation submitted in partial compliance with the requirements for the Masters Degree in technology: Homoeopathy, Technikon Natal, 1999. / The most common and difficult insect to control in the greenhouse is the whitefly. Sweetpotato whitefly (Bemisia tabaci Genn.) was the species of whitefly selected to be investigated in this trial. Sweetpotato whitefly is a major pest on a variety of plants, ranging from ornamental flowers to agricultural crops such as tomato and cotton, resulting in important financial losses. Effective control options of sweetpotato whitefly are limited. / M

In Bolivia, tomato acreage is 6717 and has a yield of 12005 kg/ha and the total production is 80,636 TM. Departments that harvest tomato are Santa Cruz, Cochabamba and La Paz, Santa Cruz being the department that shows the highest rates of production with 40653 TM in comparison with La Paz which has a production of 3109 TM and Cochabamba of 2420 TM. The principle factors in affect are, the best climatic conditions in Santa Cruz, while Cochabamba and La Paz have differences in seasonal changes (National Institute of Statistics, 1998). The importance of the tomato harvest lies in consumption preference, for the nutritional properties, as they provide a rich source of Vitamins A and C, principally for its qualities of high productivity in terms of yield per area, being a factor of great importance in the economy of the farmer. The repeated production of tomato in the same area or locality tends to create problems phytopathologicals caused by fungi, bacteria and viruses, that at times become difficult to handle, thus becoming serious limiting factors that are able to seriously affect the yields, as such the investigation of sickness control is of extreme importance. The community of Carmen Pampa belonging to the municipality of Coroico, Nor Yungas, constituting a suitable area for the cultivation of tomato, but the attack of diseases caused by fungi, principally Phytophtora infestans, with an incidence of rate of 98%, which is increased by high temperature, humidity, precipitation and fog, all of which favor the spread of this fungus. For this reason farmers are forced to use chemical products that cause problems of resistance of the causal agent of the illnesses. The FAO (1992) estimates 3 million poisonings annually at a global level of farmers and families as a result of chemicals, which cause in turn a residual effect, environmental pollution and creates and additional cost in production. In the investigation of intoxication by agrochemicals in Bolivia, in a population of 870 persons studied mentioned that, 88% are unaware of the risks associated with the use and management of using them; the cases of poisonings are more frequent in tropical plains with 46%, the valleys with 26%, the inter-Andean valleys with 14% and the high plains with 12%, without mentioning those of suicide origin. For this reason, the object of the present investigation is to try to control the late blight disease (Phytophtora infestans) in the cultivation of the tomato (Lycopersicum sculentum), with biocides, to eliminate or diminish the use of agrochemical products.

The use of pheromone-based or semiochemical lures and devices for the detection of insect pest population and monitoring in agriculture is a common practice. In many countries the use of these devices is exempt from registration requirements based on regulatory thresholds set by the relevant authorities, however, not in South Africa. The question arises whether the pheromones or semiochemicals dispensed through such devices, influence the naturally occurring compounds observed and whether a concern of toxicity and ecotoxicity is justified. A tomato field was selected in a commercial growing area of South Africa and a novel five-component lure, T.V. PheroLure®, was identified from a local manufacturer, Insect Science (Pty) Ltd. The T.V. PheroLure® consists of a Volatile Organic Compound (VOC) blend which is placed in a polyethylene bulb. Tomato VOCs were collected before, during and after the application of the T.V. PheroLure® which was used in combination with a yellow bucket funnel trap. The VOCs were collected at different heights (0 cm, 30 cm and 60 cm) of the tomato plants, from planting until harvest (22 weeks) and surrounding tomato fields without the T.V. PheroLure®. The results obtained indicated that: (i) the T.V. PheroLure® had no significant influence on the natural VOCs observed in the tomato field and (ii) that the height of sampling had no influence on VOCs observed. This study also indicated that apart from a slight increased contribution of limonene, there was no significant influence observed from the T.V. PheroLure® compounds on the natural background VOCs found in the tomato field. Therefore, it could be argued that the natural phenology of the plant has a greater influence on the VOCs observed than T.V. PheroLure® and that the concern of toxicity and ecotoxicity is unjustified when using these devices for monitoring purposes only. / Environmental Sciences / M. Sc. (Environmental Science)