Zoospores detect the presence of root hairs by sensing and responding to a number of factors, especially the chemical gradients. Various Phytophthora species are attracted to amino acids like aspartate, glutamate, asparagine, glutamine, arginine, and methionine, which are secreted by a wide range of plants. Phytophthora palmivora is drawn to isovaleraldehyde, valeraldehyde, and ante-isovaleraldehyde, which are compounds found in the root exudates of numerous plants, whereas Phytophthora sojae is attracted to isoflavones such as daidzein and genistein, which are released by soybean roots. We explored chemotaxis first in a culture dish and subsequently by observation in a microchannel, taking care to avoid any flow through the channel. We discovered that 1 wt% glucose in water was an effective attractant for Phytophthora cactorum (Figure ), that also had the advantage of being easily and repeatably prepared and low risk of triggering encystment (Supporting Information Video 2).