In order to prevent cones from being damaged by cone insects, Gravitarmata margarotana and Dioryctria abietella, sprinkler system was installed on the Pinus koraiensis Seed Orchard. Such a test was conducted at Chung-ju, Chungcheong buk-do, Korea in 2002. Insectides of Diflubenzuron 25% WP ×2,500 and Cyfluthrin 2%EC × 1,000 were sprayed at fifteen-day and twenty-day intervals during the period of insects adult occurrence by sprinkler system. The Gravitarmata margarotana generally emerged for about 53 days from middle April to early June, and peak emergence was 10 days from April 20 to April 30. Dioryctria abietella generally emerged for about 108 days from late April to early August, and peak emergence was 10 days from May 20 to May 30. Damage rate of cones were 8.7~9.7% and 10.9~12.7% on average with crown insecticide spraying with Cyfluthrin and Diflubenzuron, while 67.5% when not treated. Control effectiveness of this insecticide spraying was 85.6~87.1% and 83.9%와 81.2%, respectively. When it considers the forest environment, it is recommended diflubenzuron which is low toxic pesticide. In conclusion, effectual times and number of diflubenzuron 25% WP application with sprinkler system against cone insects were from early May through late August and six times at twenty-day interval.