POPULATION ECOLOGY Parasitization of the Red Sunflower Seed Weevil (Coleoptera: Curculionidae) by its Larval Parasitoid Triaspis aequoris (Hymenoptera: Braconidae) in Cultivated Sunflower
نویسنده
چکیده
The red sunßower seed weevil, Smicronyx fulvus LeConte, is a pest of sunßower in the northern and central Plains sunßower production regions. Weevil larvae feed and develop in the sunßower achene dropping to the soil to overwinter. A total of 630 parasitoids emerging from seed weevil larvae recovered fromNorth and SouthDakota andMinnesota from1991 to 1995was identiÞed as Triaspis aequoris Martin, a solitary koinobiont endoparasitoid. The mean parasitization rate for the red sunßower seed weevil by T. aequoris ranged from 2.5 to 24.2% per year. There was an increase in the percentage parasitization as overallweevil populations decreased over years. InNebraska, percent parasitizationbyT. aequoris, theonly species recovered, increasedwith increasingdensities of S. fulvus between1993 and1995. Patterns of emergence forboth red sunßower seedweevil andT. aequoriswere similar in two locations in North Dakota. Oviposition pattern in seeds in the sunßower head showed decreasing density toward the center, but T. aequoris parasitization was equal throughout the head. Triaspis aequoris, an egg-larval parasitoid, effectively searched for and attacked weevil eggs as soon asweevil oviposition had begun in the Þeld.Date of planting studies showed that damage fromweevils increased as seeding of Þelds was delayed, but parasitization of weevil larvae was similar among all dates. Activity by T. aequoris may have contributed to the decline of the red sunßower seed weevil from North and South Dakota and Minnesota. Lower densities of weevils also may account for the reduction in thediversity of parasitoid species of thisweevil. Theparasitoid appears to bewell adapted to its host, efÞciently parasitizes the red sunßower seedweevil and is amenable for usewith some pest management strategies in cultivated sunßower.
منابع مشابه
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تاریخ انتشار 2002