Why They Call it the Transition Zone

Spring dead spot of bermudagrass

As the old joke goes, "In the transition zone, we can grow all of the turfgrasses, we just can't grow any of them well".

The last year has been an excellent demonstration of this fact. Spring 2010 brought major problems with winter-kill in the warm-season grasses across much of the southeast. Everyone will remember the summer of 2010 as the year when record heat caused widespread failure of creeping bentgrass putting greens. 

Large patch of bermudagrass

The spring of 2011 hasn't been much kinder. Spring dead spot is particularly severe on bermudagrass this spring, and I've heard several reports of control failures from preventive fungicide applications. We've seen an unusual number of cases of spring dead spot on zoysiagrass as well (more on that next week).

Large patch (aka zoysia patch, aka brown patch, aka large brown patch....did I miss any? Seriously, can't we all just call it large patch?) is raging on all of the warm-season grasses as well. This spring is the first time I've seen large patch cause significant damage to bermudagrass in the Raleigh area. Zoysiagrass, St. Augustinegrass, and centipedegrass are affected very severely as well.

Many people struggle with these diseases of warm-season grasses because they have to be treated long before the symptoms express themselves. It is easy to forget about spring dead spot and large patch in the fall when everything is looking good. 

In addition, the economic downturn has led to severe budget cuts at many facilities, and the poor warm-season grasses are usually the ones that are left to fend for themselves without fungicide protection.

Over the next few weeks, I'll be writing in more detail about spring dead spot and large patch in the warm-season grasses. We'll cover things you can do now and during the growing season to help manage these diseases and how to prepare for preventive fungicide applications this fall. Stay tuned!

Large patch is brewing in the warm-season grasses

With cool, wet weather setting in across much of the southeast, now is the time to initiate a preventive fungicide program for large patch on the warm-season grasses. Zoysiagrass, centipedegrass, and St. Augustinegrass are most prone to this disease; large patch rarely causes significant damage to bermudagrass turf. Not all turf needs to be treated with fungicides to control large patch, but areas that have sustained severe damage in the past should be sprayed on a preventive basis.

One great advantage of the warm-season grasses is that they are fairly resistant to diseases; in most parts of the southeast, we only need to worry about one or two diseases on these grasses. Spring dead spot is a major problem on bermudagrass, and large patch can cause severe problems on all the others - zoysiagrass, centipedegrass, and St. Augustinegrass.

One problem with large patch is that it comes at a time when the warm-season grasses are shutting down for the winter or greening-up in the early spring. As a result, the potential for recovery once symptoms appear is slim to none. Once an outbreak occurs, you're probably going to be looking at those symptoms until April or May when the turf really starts growing again.

The other problem with large patch is that the appearance of symptoms is very unpredictable. Sometimes they appear in late summer, other times during the fall, and in many cases no symptoms are observed in the spring. So how are you supposed to prevent the symptoms if you don't know when they are going to appear?

The answer is easy - don't time your fungicide applications based on when symptoms have appeared in the past. Instead, you should time applications based on when the pathogen is active. As it turns out, we know that the large patch pathogen becomes active when soil temperatures consistently dip below 70 degrees at the 1 to 2 inch depth. In other words, NOW IS THE TIME TO START PREVENTIVE PROGRAMS FOR LARGE PATCH IN MANY AREAS!

There has been much confusion over the name of this disease, and as a result, very few fungicides are specifically for 'large patch'. Some labels still refer to the disease as 'brown patch', whereas others call it 'zoysia patch'. Since they are all caused by Rhizoctonia solani, any fungicide that has one of these diseases on the label can be used for large patch control.

In some cases, one well-timed fungicide application in the fall can provide season long control of large patch. However, in severely affected sites, where disease pressure is high, repeated applications are often necessary. Two applications in the fall, 4 to 6 weeks apart, and one application in the spring when the turf is nearing full green-up is the ideal program. If three applications are not possible financially, the fall applications are probably more important than the spring application.

Strong brown patch fungicides like Heritage (0.4 oz of 50WG or 2 fl oz of TL), Insignia (0.9 oz) and ProStar (2.2 oz) are very effective for large patch control. Some of the DMI fungicides, Bayleton (1 oz) in particular, have performed very well also. Recent trials have also shown that Headway (3 fl oz), a pre-mix of Heritage and Banner, is a very effective large patch fungicide.

For more information about large patch management with fungicides and cultural practices, please refer to our Large Patch Disease Profile on TurfFiles.