For the design of the device, we proposed a simple cytometer concept, where zoospores would be detected by the change in electrical impedance in a channel, when a zoospore passed into the gap between the two electrodes (Figure ). There are six issues to address: 1) detection of the zoospore, determined by the minimum reliably detectable impedance change and also by the transit time of a zoospore across the electrode gap; 2) sampling of a sufficient volume of solution given that the zoospore concentration might be low and variable; 3) specificity of detection, to discriminate against other particulate matter that might be present; 4) guiding or driving zoospores to enter the sensing channel, which can be achieved by using a syringe pump/chemical attractant and a suitable design of the channel shape; 5) prevention of encystment of the zoospores in the channels, which happens if the spores are in a stressful liquid environment; and 6) the design of an instrument system that was of reasonably low cost that could be used in-field and adapted for remote measurement.