An apparatus for collecting total conidia of Blumeria graminis f.sp. hordei from leaf colonies using electrostatic attraction

Conidia from living conidiophores of barley powdery mildew ( Blumeria graminis f.sp. hordei ) on host leaves were collected consecutively using an electrostatic spore collector. The collector consisted of an electrical conductor plate linked to an electrostatic voltage generator and insulator plates placed abreast on a timed conveyer. The conductor plate was negatively charged by the potential supplied from the voltage generator. The negatively charged conductor plate caused dielectric polarization of the insulator plate, and the surface charge on the insulator plate attracted mature conidia abstricted from conidiophores on colonies growing on leaves placed 2 cm from the insulator plate. The surface charge on the insulator plate was proportional to the voltage applied to the conductor plate. Under optimized conditions, abstricted conidia were attracted to the electrostatically activated insulator plates without any detriment to their survival. During a colony's life span of c . 460 h, conidia were released throughout the day and c . 12 × 10⁴ conidia were collected during the lifetime of the colony. This is the first report on the direct quantification of progeny conidia produced by powdery mildew infecting host leaves.