1. aquatic plants that lack a vascular system. Some are microscopic and others are large. Examples are pond scum, kelp and red tides.
The wet condition the past few weeks have resulted in the presence or potential presence of algae. During this time of the year little turf injury is associated with algae and once dry conditions occur the amount of algae present will reduce. Algae however can produce scum or mucilage that can seal the soil surface resulting in reduce air exchange between the atmosphere and the soil. Once a sealing occurs turf decline is often rapid especially during periods of hot humid weather. Surface sealing caused by algae is most prevalent on shaded greens, poorly draining greens, or thinly covered turf. Situations where algae are a chronic problem be proactive in preventative treatments. Improving drainage, air movement, judicious irrigation and raising the height of cut are important practices for improving the environment for turf growth and minimizing algae effects. Spiking is a mechanical practice that helps reduce surface sealing and promotes air exchange. Frequency of spiking varies. Some people recommend spiking every 3 to 4 weeks. I tend to favor more frequent spiking where algae are a potential problem. The fungicides - chlorothalonil and mancozeb - are effective in controlling algae especially if applied preventatively. Regarding the potassium salts of fatty acids or the quaternary ammonium compounds, we do not have much data or experience to make a recommendation.