Efficacy of Azadirachta indica seed extract against leaf miner on lemon seedlings under Namibian nursery conditions

This study compared the effectiveness of two concentrations of Azadirachta indica (neem) seed extract in controlling citrus leaf miner (Phyllocnistis citrella) infestation on lemon seedlings. The experiment was conducted at the University of Namibia, Ogongo Campus Tree Nursery, using a Completely Randomized Design with three treatments replicated four times. The treatments comprised of neem Seed Extract Concentration 1 (1.5 kg/10 L water), neem Seed Extract Concentration 2 (2.5 kg/10 L water), and a control (tap water), applied to twenty lemon seedlings per treatment over five months. A two-way ANOVA indicated that treatment, time, and their interaction significantly influenced infestation percentage, leaf desiccation, and estimated leaf curling extent (p< 0.001). Treatments accounted for the greatest variation in infestation percentage (38.13%) and leaf curling extent (24.05%), while time contributed most to variation in leaf desiccation (36.29%). The control group recorded the highest infestation (51.1%), followed by neem seed extract concentration 1 (23.3%), and neem seed extract concentration 2 (23.2%). No significant difference was observed between Concentration 1 and Concentration 2, indicating that both neem extract concentrations significantly reduced infestation compared to the control. Leaf desiccation differed significantly among treatments, with the control group showing the highest desiccation (28.43%), followed by neem seed extract concentration 1(13.27%), and neem Seed extract concentration 2 (10.54%). Similarly, the highest leaf curling extent was recorded in the control group (3.238), followed by neem seed extract concentration 1 (2.342) and neem Seed extract concentration 2 (1.975). Across the study period, infestation and associated symptoms increased, with December exhibiting the highest infestation rates and leaf damage. These findings demonstrate that neem seed extracts are effective in mitigating citrus leaf miner damage in lemon seedlings, supporting their potential use as sustainable alternatives to synthetic pesticides.