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Aqueous necm seed kernel extract was tested for its effectiveness against eggs and larvae of the leafminer, Leucoptera malifolzelln Costa. When treating eggs with extracts from kernels of different origins, the results were inconsistent. The extract obtained from a batch of kernels (20 g kernels/liter) gave a 60 Yo reduction of the hatching rate, while no significant reduction was obtained when using kernels from another batch (at 25 g/liter). In both experiments the growth of hatched larvae was disrupted and no pupation occurred. A concentration as low as 1.25 g/l of the more effective kernels caused 80 % of larval mortality. 100 % mortality was obtained when treating 1st and 2nd-3rd instar larvae with 5 or 20 g/l extracts. In persistence tests, the extract was found to be still very effective 12 days after treatment. Systemic activity was confirmed either when applied as a soil drench or when sprayed only on the lower leaves of the plants.