The study was conducted at Sakha Agriculture Research Station Farm and the laboratory of field crop pests research department, Plant Protection Research Institute (PPRI) at Sakha to evaluate the influence of planting date and age of maize plants on the degree of infestation by Pseudonapomyza spicata Mall. and study also distribution pattern of this insect mines on maize (Zea mays  L.) leaves. Data showed that this leaf miner infested maize plants of July plantation as highest, followed by maize plants of June and September plantations. However, maize sown during April or May was insect-free. The leaves of 30-days old were the most infested with the leafminer, P. spicata followed by those of 20- and 10-day old. Older than one month, maize plants were not preferred by P. spicata. The infestations with P. spicata were concentrated in the lower leaves, and then the damage became slighter toward to the top of the plant. The insecticide, Gaucho 7% WP used at rate of 7 or 14 g/kg maize seed as seed-coating effectively reduced the infestation with P. spicata. This treatment is less harmful to natural enemies, because the insecticide is used with seeds not as a spray onto maize plants.