| Summary: | 碩士 === 國立臺灣大學 === 植物醫學碩士學位學程 === 103 === Organic agriculture is a system aimed at producing food with minimal harm to ecosystems, animals and humans. The organic yields are 25% lower than conventional ones, and the yield differences are highly dependent of ecological balance between argoenvironment and culture practices. As located in subtropical area, the weather in Taiwan is usually hot and humid, resulting in the fact of frequent occurrence of insect pests that pose enormous threats to the crop. To date, major interests of materials for controlling insect pests in organic agriculture system rely on natural product including plant oils, plant essential oils, plant protection agents and mineral materials. The present study is to identify safe and cheap natural product such as plant oils blended with plant secondary metabolites to control Lipaphis erysimi. A variety of plant oil including soybean oil, sunflower oil, blended oil (mixture of sunflower oil, canola oil and safflower seed oil) was emulsified using liquid soap (CRYSTAL® ). No significant difference was found among tested plant oil emulsion in term of control rate experiments (up to 75%). Based on mortality of Lipaphis erysimi, the LC50 of sunflower oil was 5.53 mL/L; the LC50 of blended oil was 5.14 mL/L; the LC50 of soybean oil was 2.44 mL/L; the LC90 of sunflower oil was 12.95 mL/L, the LC90 of blended oil was 17.89 mL/L, the LC90 of soybean oil was 6.42 mL/L. The LC50 and LC90 of soybean oil were lower than sunflower oil and blended oil. Soybean oil costs NT$ 388 per hectare and is more economic than others. Infusion solutions from artemisias, peppermint, patchouli and tobacco were combined with plant oil emulsion and used as plant protection agents. Control rates of tobacco infusion solution complex (soybean oil emulsion 1,000X + tobacco of infusion solution 100X) were 87.6%. Control rate of plant protection agents are significantly greater than soybean oil emulsion alone. Yield loss 15% of the organic vegetables with high population density of L. erysimi (maximized with minimum of 300 L. erysimi in 1.5 m × 1.5 m area). Soybean oil LC50 concentration + tobacco infusion solution 100X was suggested to control L. erysimi during peak season (from September to February of next year) in Taiwan. When L. erysimi high population density (reaches 300 per 1.5 m × 1.5 m area), it is suggested to control aphids using soybean oil at LC90 concentration + tobacco infusion solution 100X. During season with low population density of L. erysimi, soybean oil emulsion 1,000X + tobacco infusion solution 100X were suggested. The study demonstrates that importance of environmental factors such as temperature in controlling L. erysimi by using plant protection agent or soybean oil emulsion.
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