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I have been away at training this week. Every time we have training, there has been a tropical storm or hurricane lately. This one was not that bad thank the Lord. However, this did give the Turfgrass Staff at the University something to talk about in our training, especially from a disease standpoint.

Wet and humid conditions can be a great opportunity for disease development. There are a range of issues we could be seeing during this storm from pythium to large patch. We do not talk much about large patch this time of year but perhaps we should.

The most recent research indicates that our efforts on large patch are much more effective when applied at the right time. Time implies a certain date or time of year, but that isn’t necessarily the case. What we need to monitor to know when to apply fungicides for large patch prevention is the soil temperature.

In our area, large patch affects St. Augustinegrass, centipedegrass, and zoysiagrass. When working in St. Augustine or centipedegrasses, the magic soil temperature is 80°F. When we are 80° for three days then it is time to make an application. Zoysiagrass applications can wait until we hit 75° soil temperatures.

I say we do not usually talk about large patch at this time of year because it is normally early to mid-September before we start seeing the 80° soil temperatures here. I pulled the soil temperature data from the Tidewater Research station and was alarmed to find that we were under that threshold for six days in late July and with the onset of this storm, we have been below 80°F for the past five days (climate.ncsu.edu). Remember, we cannot cure this disease with fungicides, prevention is our only method of control. We may have missed our timing already for this season.

If you do not know what large patch is you should come to more of my classes! Large patch is a turf disease that affects the sheath of the grass. In our area, it is mostly an issue in centipede and St. Augustine grasses. In other areas, zoysiagrass seems to be most affected by this disease. The disease is most active in the fall when temperatures drop. This is when it does damage. Grasses infected with large patch will have large patches that do not green-up the following spring. Some years this disease is very prevalent and others we hardly see it. Disease development can be accelerated with thatch build-up, high mowing heights, and cool but humid weather.

In St. Augustinegrass, infections will display a yellow to orange ring or halo in the grass. In centipedegrass, the halo will appear to be black or purple when viewed from a distance. The turf will die or just not green back up in the spring inside of the ring. If not treated, the rings will grow every year. If you have had large patch in the past, you will more than likely have it continually moving forward. Again, prevention is the best medicine. Using fungicides that have the active ingredient azoxystrobin or a combination containing this active ingredient have the best efficacy.

If you are having an issue in your home garden or landscape, send your questions to Gene Fox, Consumer Horticulture Agent with the North Carolina Cooperative Extension Service, please email Gene at gene_fox@ncsu.edu or call at (252)946-0111. You can also ask to speak to a Master Gardener! On Mondays and Wednesdays between 10:00 and 12:00, they are on the Greenline to answer all home horticulture questions. Check out our Facebook page, Beaufort County Master Gardeners, for The Plant of the Week and Food Garden Friday. We are having an Extension Master Gardener Volunteer training starting in September. If you would like to know more about this program, please plan to join us on August 12 from 10:00 – 12:00. Until then, happy gardening!