Brown Patch: the big nasty turf spoiler

Rhizoctonia solani…

Brown patch is caused by the ubiquitous pathogen, Rhizoctonia solani, and it infects virtually every species of turf in the US. Tall fescue and turf-type fescue is far more susceptible than Kentucky bluegrass, but the latter gets it, too. In zoysiagrass this same organism causes zoysia patch disease. For you golfers, blame those ugly summer greens on brown patch! Seedling turf is extremely susceptible to brown patch, which is why most experts discourage spring seeding.

The fungi lives on decaying organic matter in our lawns, at the interface of organic matter and the soil surface. It rears its pathogenic side during prolonged periods of hot and humid weather, especially during dry spells. You can bet your bum that when the dew points and the night time lows are in the 70’s, we’ll have an outbreak. For photos, just Google “brown patch in fescue turf” for more pics than you can handle. I’ll tell you right now that 95% of disease in Midwestern transition zone turf is brown patch.

There are numerous cultural practices that you should employ in an attempt to minimize the impact of brown patch on your lawn, but to really control this disease, you’ll need the help of fungicides. First, let’s talk about those things you can manage from a cultural perspective.

  1. Keep the blade sharp:  No, I’m not talking about the 7 habits bull crap. Literally. Keep. The. Blade. Sharp. (My daughters tell me this infers extreme emphasis…does it?) Come mid-May, you should be sure to have a brand-new sharpening job on that blade. Buy an extra and always have a sharp one handy.  Don’t go more than 3 months without sharpening your blade (average homeowner).
  2. Keep the deck high:  Mow cool season turf in full sun at maximum height on your mower. 4 inches is better than 3 inches! For cool season turf in good shade, you can mow lower, say 2.5 inches, because you don’t want turf to stay wet from dew, irrigation or rainfall excessively long. If you’re serious about being the beast of turf in your neighborhood, you should have a reasonably new mower, capably of 3.5 or 4 inch mowing heights.
  3. Water in the morning:  All diseases need moisture for the spores to germinate and grow. Watering at night keeps the grass covered in a film of moisture all night long. Thus, more disease.
  4. Bag your clippings in the dog days of summer:  Bagging the diseased-laden grass when the outbreak is bad has been shown to reduce the spread of the disease. When you’re miserable outside so is your turf. I like to tell folks when the heat index is above 90F, your turf isn’t happy. When the heat index is above 100F, your turf is pissed at you…for watering it, fertilizing it, and doing all those things to keep it from going dormant.
  5. Avoid excessive nitrogen in June, July and August:  Points 1 to 4 are important, but my experience shows that 90% of you with terrible brown patch used the wrong fertilizer at the wrong time. Anybody putting traditional, synthetic fertilizer formulations down after mid-May is begging for the disease. You don’t want soft and succulent turf around when the conditions are right. The biggest national brand sells stuff so high in nitrogen it should only be used on zoysiagrass in the summer. Weed-and-Feed formulations are terribly high in nitrogen. They suck! Both for killing weeds and too much N…I’ll save this rant for later this summer. Seriously, cool season turf in St. Louis and the rest of the transition zone should get 75% of its nitrogen in the fall, to support the plant’s natural growth cycle. Using high nitrogen fertilizers in the early spring isn’t a death knell, but your crabgrass product is best with 12% or less nitrogen. Retail stuff sucks, with 24% or more nitrogen in the bag. And retail stuff has a crappy herbicide, too. Your grass will green up wonderfully in the spring if you do most of your fertilizing in the fall. The astute reader is now asking herself, “Well then, what the hell SHOULD I use in the summer?” I love organic nitrogen in the summer, but ONLY for irrigated lawns. I especially like Milorganite (and the knock offs) for irrigated turf, because it has low nitrogen content, all slow release, and a lot of iron. If you’re not irrigating, don’t fertilize after your crabgrass product goes down. Reread that–if you’re NOT irrigating in the summer–DO NOT fertilize in the summer!

Fungicides

It’s important to use the right product for control of brown patch, which is azoxystrobin (I pronounce it “a-ZOX-e-stroh-bin”, but I’m not the sharpest tool in the shed!). A disease program MUST contain this active ingredient, proven by universities to be the best single fungicide for brown patch. However, it should not be used alone! The best companion product is propiconazole (pro-PEE-con-a-zole).

Fungicides aren’t cheap. Actually, they are very expensive, especially considering you need to apply them every 3 to 4 weeks during the dog days. No matter the product you use, read the label and follow the coverage recommendation for brown patch. If you stretch it too far you’re wasting your time and money. Just burn those bills on the BBQ…or better yet, send them to me!

There’s a commercial product available at professional turf outlets called Headway G.  A 30 lb bag covers 10,000 sq ft on a preventative basis, but only 5,000 sq ft on a curative basis. If you’re just now reading this (mid-June-2018), your first application is in the CURATIVE dose rate. When I was in the business we’d instruct our Sward Masters to make their first preventative application a full week ahead of the prolonged 90 F degree weather forecast.  If we get a wonderful clearing cold front that drops our temps and humidity, stretch it to the 4 week interval.

The photos below show the Scott’s product containing azoxystrobin (DiseaseEX) and the Bayer product with propiconazole. I’d recommend you buy both for your first shot. Apply them both, individually of course, if your lawn is suffering terribly. Each bag covers 5,000 sq ft. Used alone, the manufacturers suggest applying every 2 weeks in miserable weather, every 4 weeks otherwise. But that’s used alone.

After application water well, in the AM. Then in 3 weeks apply azoxystrobin again. Three weeks later apply propiconazole. Repeat until the cool weather arrives (crap, that’ll be October!). And oh, by the way, don’t count on 100% control! Ain’t gonna happen. Be happy with 80% control.

Let me know if you give these products a go!

Stay Cool!

Trav

 

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