Potential of Botanical Extracts in the Control of Kale Aphids (Brevicoryne brassicaea) and Their Effect on the Parasitic Wasp (Aphidius ervi)

The use of synthetic pesticides has made important impacts on aphid control. However, it has limitations due to the development of aphid resistance and negative effects on human health and the environment. In this research, we explore alternatives to pesticides by examining the effectiveness of plant extracts (Mexican marigold, Sodom apples, garlic and ginger) on reducing populations of the kale aphid while preserving its parasitoid, Aphidius ervi. Use of botanical plants would be of importance to small scale farmers due to their availability, affordability and environmental friendliness. The research was laid out in a Randomized Complete Block Design with three replications. Aphid numbers, mummified aphid numbers as well as parasitic wasps were counted; data was analyzed using Statistical Analysis Software (SAS) and mean separation done using Tukeys. Garlic extract was the most effective in control of aphids causing a reduction by 69.5%. Mexican marigold extract was the most effective as compared to garlic extract which controlled high percentage of kale aphids but was very lethal to the Aphidius ervi. Nonetheless, Mexican marigold extract was least effective in the control of aphids.