关键词: 三化螟, 捕食率, 寄生率, 种植密度, 生育期

Abstract: The incidence of predation and parasitism on egg masses of the yellow stemborer Scirpophaga ineertulas (Walker) and related natural enemy populations were monitored under four rice planting densities (900000, 660000, 550000, and 160000 hills/ha) and growth stages (20,40,60 and 80 days after transplanting [DAT]) for two seasons. Egg predation was significantly higher at 20 and 40 DAT but not at the later stages although the predator populations increased as the planting density increased and season progressed. Conversely, egg parasitism declined as the plantingdensity increased and season progressed. At the higher planting density and later in the season parasitism declined along with number of species per egg mass. In general, egg mortality caused by predators and parasites declined significantly as the plantingdensity increased and the season progressed even though the enemy population increased. The significance of conservation and utilization of natural enemies of rice pests by manipulation of the planting density is discussed.

Key words: Scirpophaga incertulas——predation——parasitism——planting