Evaluating Neem Oil and Water Extracts for Aphid Control and Growth Performance of Brassica napus in Zambia

This study investigated the effectiveness of neem oil and neem water extracts in controlling aphids and improving the growth of Brassica napus in Zambia. Aphid infestation severely limits Brassica napus production, and many smallholder farmers rely on costly and environmentally harmful synthetic pesticides that are losing effectiveness due to resistance. With neem trees widely available across Zambia, this research sought to generate field-based evidence for sustainable, low-cost botanical pest management. A quantitative experimental approach was used, applying a Randomized Complete Block Design (RCBD) with a sample size of 90 plants, and the study was conducted at Maamba Boarding Secondary School in Sinazongwe District. Data were collected over six weeks through aphid counts, mortality assessments, plant height measurements, leaf characteristics, vigour scoring, and yield evaluation. Results showed that neem oil achieved the highest aphid suppression, reducing aphid population from 136 to 2 per plant corresponding to mortality rate of 92.7%, followed by neem water at 78.3%, while the control recorded only 12.5% natural mortality. Neem oil also produced superior vegetative growth and increased marketable yield by 42% over the control. The study concludes that neem oil is an effective, affordable, and eco-friendly alternative to synthetic pesticides, contributing to practice through a farmer-ready solution, to policy by supporting reduced chemical pesticide dependence, and to theory by validating neem’s dual pesticidal and growth-enhancing functions.