A pattern of dark green dots approximately 0.5-0.75 inch in diameter is often observed on many putting surfaces in the West in spring. What causes the polka dot symptom? There could be a couple of reasons.
The dark green polka dots are typically in the same exact pattern as the most recent core aeration treatment. The grass and roots growing within the aeration hole has better oxygen exchange in the rootzone and is healthier than the surrounding turf, which is growing in soil with more thatch and organic matter content and less space for oxygen exchange.
Another potential cause for the dot symptom is elevated levels of soluble salts between the green dots. Soil with high levels of organic matter and thatch can retain salts and sodium, causing a yellowing symptom on turf. To verify if soluble salts are the problem, use a portable electroconductivity meter (EC meter) to check salt levels in the green dots and the yellow area between the dots.
So, what are the green dots telling us? Here are a few take away messages:
- The green dots tell us that core aeration and sand topdressing is good for turf. The grass is much happier and healthier above the aeration hole where the roots get more oxygen. It is a sign that more core aeration is needed to affect more of the putting surface and address the areas between the green dots.
- If the yellowing between the green dots is the result of elevated soluble salts, the greens should be deeply watered – i.e., leached – one week before the next aeration treatment to flush the salts beyond the rootzone. Leaching the greens after aeration is not as effective because water moves rapidly down the aeration holes without adequately flushing the area between the holes.
West Region Agronomists:
Patrick J. Gross, regional director – pgross@usga.org
Larry W. Gilhuly, agronomist – lgilhuly@usga.org
Brian S. Whitlark, agronomist – bwhitlark@usga.org
Information on the USGA’s Course Consulting Service
