菜蛾啮小蜂的生物学及温度对其种群增长的影响

Biology of Oomyzus sokolowskii and effect of temperature on its population parameters

菜蛾啮小蜂Oomyzussokolowskii (Kurdjumov)是小菜蛾PlutellaxylostellaL .的一种主要寄生天敌。观察表明 ,该蜂喜产卵于小菜蛾各龄幼虫 ,也可产卵于预蛹 ,进行幼虫至蛹期的跨期聚寄生。每头寄主蛹出蜂多为 5～ 10头 ,平均 7 8头 ,其中雌蜂占 85 %～ 90 %。该蜂也可产卵于在小菜蛾幼虫体内寄生的菜蛾绒茧蜂高龄幼虫 ,故又是小菜蛾的兼性重寄生蜂。在杭州 ,每年该蜂在田间的活动期为 4～ 10月 ,10月中下旬陆续以老熟幼虫或预蛹进入休眠越冬 ,第二年 4月陆续羽化并开始产卵寄生。该蜂发育、存活和繁殖的适温范围为 2 0～ 30℃ ,低于 2 0℃或高于 30℃对其存活不利 ,但在适温下发育羽化的雌蜂 ,短时间内在 32～ 35℃高温下仍可大量产卵寄生。在2 0℃、 2 5℃和 30℃下 ,平均每雌一生可寄生小菜蛾幼虫数分别为 3 1、 13 2和 6 8头 ,产子蜂数分别为 2 0 5、 92 1和 5 0 4头 ,内禀增长率分别为 0 0 82、 0 2 40和 0 2 6 3(雌 /雌·天 )

Oomyzus sokolowskii (Kurdjumov), a major parasitoid of the diamondback moth, Plutella xylostella L., is a larval pupal parasitoid that prefers ovipositing into host larvae of all instars but depositing its eggs in host prepupae too. The parasitoid can also deposit eggs into grown larvae of Cotesia plutellae (Kurdjumov) that have been parasitizing the larvae of diamondback moth. Thus, O. sokolowskii is a facultative hyperparasitoid of the diamondback moth In Hangzhou, the parasitoid is active in the field from April to October, and enters into a quiescent state as matured larvae or prepupae inside the hosts in mid to late October to overwinter until next April. Laboratory experiments showed that the favourable temperature for development, survival, and reproduction of the parasitoid ranged from 20 to 30℃, and temperatures below 20℃ or above 30℃ were unfavourable for its survival. However, the wasps that developed and emerged at favourable temperatures could effectively parasitize the host at 32～35℃ in a short period of time. At 20℃, 25℃ and 30℃, a female wasp on average parasitized 3 1, 13 2 and 6 8 larvae of the diamondback moth, and produced 20 5, 92 1 and 50 4 offsprings, respectively. The intrinsic rates of increase ( r m) of the parasitoid at 20℃, 25℃ and 30℃ were estimated to be 0 082, 0 240 and 0 263 female/female/day, respectively.