The seasonal occurrences of Ostrinia furnacalis and its egg parasitic wasps on sweet corn in Pearl River Delta Region

Chinese. 系统地研究了珠江三角洲地区亚洲玉米螟Ostrinia furnacalis (Guenée)在甜玉米地的周年发生动态、产卵寄主选择与甜玉米生育期的关系、卵期寄生性天敌种类、优势种寄生蜂及其种群消长规律以及玉米螟赤眼蜂Trichogramma ostrinia Pang et Chen对亚洲玉米螟的控制作用。结果表明，在这一地区的甜玉米上除在1月份没有查到玉米螟落卵外，2～12月均有产卵，种群动态呈现明显的单峰型，即5～8月是亚洲玉米螟发生危害的高峰期。亚洲玉米螟成虫产卵对甜玉米植株的生育期具有明显的选择性，以抽雄期的植株对亚洲玉米螟产卵最具吸引力。玉米螟赤眼蜂是当地亚洲玉米螟卵期寄生蜂的优势种。甜玉米田赤眼蜂寄生率的季节变化符合典型的天敌跟随现象，即2～6月卵块寄生率较低， 7～9月是赤眼蜂寄生的高峰期，田间寄生率可达90%以上。

English. The Asian corn borer (ACB), Ostrinia furnacalis (Guenée), is the most destructive insect pests limiting the production of sweet corn in the Pearl River Delta Region. Current control practices are largely limited to the application of broad spectrum insecticides that can cause serious hazard problems. Trichogramma release is an alternative biological control method which is environment friendly and safety to the human. The efforts were conducted to investigate the seasonal variation of ACB, oviposition by ACB in relation to sweet corn developmental stages, ACB egg parasitism species, the seasonal variation of Trichogramma parasitism on ACB, the dominant species of ACB egg parasitisms. ACB egg masses could be observed in the sweet corn through February to December with a single peak ranged from May to August. ACB females prefer significantly to lay egg masses on the corn plant at tasselling stage. T. ostrinia was the dominant species of ACB egg parasitoids. The parasitized ACB egg masses by Trichogramma spp. could be observed from April to December with a single peak ranged from July to September. The parasitism could be as high as 90%, which played an important role in controlling ACB. The seasonal dynamic of Trichogramma parasitism was typically adapted to the natural enemy following-up pattern.