5.During the tobacco hardening period, bed of tobacco seedling was the falling target of alate aphids, and was the main resource of tobacco virus spread by aphids.

• 炼苗期烟草苗床是传毒介体有翅蚜着落的靶子中心 ,是烟田蚜传病毒病的主要初侵染源 ,为防治烟草蚜传病毒病的关键时期。