Turf Reports: Fungicides presented by PBI-Gordon

Fungicide refresher

Dr. Brian Aynardi spends large portions of his days studying fungicides and the diseases they are intended to control.

Aynardi is PBI-Gordon’s Northeast research scientist. His role requires managing the company’s university and contract research efforts within his territory. He joined PBI-Gordon shortly after earning his doctorate from Penn State in 2016. He’s a go-to source for all things fungicides.

Golf Course Industry spoke with Aynardi about selecting the right fungicides for your course and ensuring they are maximized when controlling disease. His insight will help you develop a solid fungicide approach in 2024 and beyond.

Why fungicides …

Disease is a little different than weeds. If you see a broadleaf weed, you can go out and make one or two applications depending on the type of weed and you’re typically going to control that weed. With diseases, you want to prevent them from occurring. Fungicide is really a misnomer. Fungicides actually go into the plant if they are penetrant fungicides. They will cause fungistasis in the plant and temporarily stop the pathogen from causing disease. But as leaf tissue is regularly removed or the chemical degrades, and as the concentration of that toxicant becomes low, the fungus is able to start growing again.

Let’s say you’re in the Northeast or Mid-Atlantic. Dollar spot conditions can persist for months on end and you’re going to have to make repeated applications. Because of the ability of pathogens to mutate and develop resistance to certain classes of chemistry, and because of the degradation of the fungicide, you’re going to make a lot more fungicide applications in a year than you’re going to make broadcast herbicide applications.

Fungicide selection methodology …

Generally speaking, fungicides are safe across the board on most turf species. There are a few like some of the older DMIs you have to be careful with during transition around warm-season grasses.

The biggest things for a superintendent to consider when they are looking at a new fungicide … What are my top one, two or three problems? What am I spraying that maybe isn’t working or when I see disease pop up? What were the last one or two applications that I made prior? Perhaps a new fungicide will enhance control of those problems better than what is currently used.

When you’re evaluating a new product, go to university partners and talk to people who have actually evaluated it under controlled conditions. Usually, those controlled conditions are more severe than what you’re going to see in the field. Get some feedback and do your own demo. Talk to your distributor sales rep and see what they are willing to tell you about the chemistry and their background with it. If you can’t get it from your distributor rep, ask if you can chat with the manufacturer rep.

Another thing to look for is that if I’m spraying for dollar spot and there are 15 products that contain an SDHI for dollar spot, look for a different class of chemistry. Don’t just look for a different brand name. Make sure you are rotating different groups properly, because if you are using the same group over and over, you’re just using different names. Or if you are using post-patent products that have a different name — but it’s the same AI — you’re not rotating. You’re creating a resistance scenario. You need to look outside the box and look for different modes of action that maybe you haven’t tried.

Evolution of fungicide chemistry …

The chemistries today are a lot more site-specific than the chemistries of old. We use much more environmentally friendly chemistries. A lot of times that results in repeated applications and sometimes on shorter intervals. You have to reapply nowadays on a more traditional 14-, 21- and up to 28-day interval. That’s kind of the thing with new products. Due to their specificity, the potential for resistance is greater. You might not get the longevity of stuff that you sprayed that’s much older, but it’s more environmentally friendly.

Tank mixing …

One of the most common calls we get in the R&D and tech sector is, ‘Can I mix this with this, with this, with this, with this, with this and with this?’ and they put 15 things in the tank. The short answer is that we don’t always know, especially if you’re putting in a product that’s really going to drop the pH and the rest of the products in your tank mix are higher pH.

When you are tank mixing, just don’t pick five different products, because if you pick five different products that all contain a DMI, and put five different DMIs in the tank, you’re not tank mixing. You’re just putting a lot of stuff in there with the same mode of action. You need different modes of action.

The benefit of tank mixing is that you are targeting the pathogen with a number of different modes of action. If you put chlorothalonil or another multi-site active in the tank, or if you use fluazinam, which is considered somewhat of a multi-site active ingredient (though designated FRAC 29), you’re kind of confusing the pathogen because you’re hitting it in a lot of different areas. A simplistic thing my advisor used to say during class, ‘It’s a shotgun vs. a rifle effect.’ If you take a number of different modes of action and you target that pathogen of interest with a shotgun, you are throwing out a lot of different things at it. If you’re hitting it with a rifle each time, and you’re hitting the same spot, eventually the pathogen is going to evolve and get beyond that.

Any time you’re doing a tank mix I always advise a jar test because you just never know, and it can vary by manufacturer. Even if you have the same AI, maybe they have a different milling process or maybe they have different co-formulation packages.

Getting fungicides to work as intended …

The biggest thing with fungicides is what is your target pest? Is your targeted pest a foliar pathogen or is it a root-borne pathogen? If you’re going after a root-borne pathogen, something like spring dead spot, take-all root rot, Pythium root rot, you need to make sure you immediately get water on that after the application. Even fairy ring would be another one. For example, Segway, if you don’t get water on that within three to six hours, you will start to lose some efficacy after six hours. I’m not saying it’s not going to work. It might be a 5 to 10 percent reduction, but because you’re spending a lot of money to make these treatments, water it in immediately.

But if you’re doing a foliar application and using something like fluazinam or chlorothalonil, you absolutely don’t want to water it right away because that’s just going to wash it off the plant surface and reduce the efficacy substantially. Make sure you know what pathogen you are going for.

What to expect from a manufacturer …

Our manufacturer sales reps work with distributors. If there’s an issue, or somebody says, ‘I sprayed product X and I didn’t get the efficacy that I wanted to see,’ talk to their distributor rep. They will contact the manufacturer rep and a lot of times it will go to the tech service and R&D teams. They’ll ask, ‘Why did this not work?’ It could be a number of different things. But, at PBI-Gordon, we stand by our products and will support you.

If they want to problem solve on their own, questions will include: What is the carrier volume? Am I getting adequate coverage? What disease did you go out for? If you went out for Pythium root rot, and you didn’t water it in for 24 hours and you’re getting break through, a little bit of that is on the superintendent to know the best way to use a product and best post-treatment application method if it’s a root disease.

We are here to answer your questions if you are not getting control. Because there are so many products on the market and manufacturers have so many different recommendations, there’s a chance maybe you’re not using the product as entirely as intended. There are so many little things on a label that can be missed. But if you don’t understand, or you do get break through and you still don’t understand, there’s a potential you do have resistance. If you’re spraying SDHIs and you have SDHI resistance and you’re not getting good control, the manufacturer should be there to explain that you probably should use different modes of actions and switch to different products.

First-person thoughts about fungicides

Superintendent Ron Furlong explains what makes a disease control solution the right fit for the course his team maintains.

When I first became a superintendent (around the turn of the century), fungicides were an important tool, although I honestly didn’t put enough thought into why I was spraying what I was spraying. I just did what superintendents I had worked for in the past had done. You knew what worked and you went with it.

As I grew as a superintendent and began to educate myself more, including talking more with distributor and manufacturer reps and other superintendents, I slowly began to put more thought into fungicide selection and use. Around this time green speed became the ultimate goal, and the result of everyone lowering mowing heights and stressing out our turfgrass more than we ever had before produced increasingly higher disease pressure.

For instance, a disease like anthracnose, at least for us here in the Pacific Northwest, hadn’t been the huge issue before the late 1990s that it is now. But as we all became obsessed with green speed and roll, suddenly a disease like anthracnose became a major issue for us.

So, I began to question everything about disease and fungicide use. What was I trying to do as far as disease control? Was I making the right choices throughout the year? Was I flying from the seat of my pants, or did I have a plan? Curative versus preventive? Was I using the best possible products I could as far as protecting, to the best of my ability, our course and the environment?

As I started questioning these things, technology began helping us all as well. Better fungicides slowly became available. Not only were fungicides more effective, but their chemical compositions provided longer control at lower rates.

With chemical restrictions hitting our industry hard, superintendents had no choice but to look deeper into how we were controlling disease. And this goes beyond just chemical use. We began to experiment with cultural management practices that could help with lowering disease pressure.

Aerification. Raising mowing heights. Rolling instead of mowing. Reducing shade. Timing and amount of irrigation. Fertility, which includes not only fertilizer selection, but how much of each product and the timing of those applications in conjunction with fungicides, plant growth regulators and wetting agents. And, in drastic cases when nothing else was working, actually changing the turfgrass variety.

Superintendents never consider just fungicides alone in the battle with disease pressure. There’s so much that can go into it.

But, for the sake of this article, let’s get back to fungicides. And let’s look at this simple question: What makes a fungicide a good one for me?

Here are the main things I look for in a fungicide:

1. Length of control
2. Is the use rate low?
3. What specific diseases does it control?
4. The effectiveness of the product when used in a preventive program

Let’s take a quick look at these four things:

Length of control

This varies depending on if you are using a fungicide curatively or preventively. The fungicide program I am on, which I have been following religiously for about four years now, is almost entirely preventive. Because of the success of this particular program for me, curative applications have become rare.

So, when I do tweak the program from year to year and I’m considering adding or dropping something in the rotation, I’m always considering the timing of the product and how long of control I can get out of it.

Adding or dropping one chemistry in your program will literally affect everything else in the program if the timing of control doesn’t quite fit.

Low-rate use

The first fungicide that I can remember coming available to us that advertised exceedingly low rates was azoxystrobin. I’m not saying this was the first fungicide to be marketed with an extremely low rate of use, but it was the first one that really caught my eye.

I was fascinated with a product that could be put out at such a low rate. It was an eye-opener. Unfortunately, not all low-rate fungicides are going to work for each particular situation. All golf courses are unique in respect to disease environments regardless if they have the same turfgrass varieties as other courses. For instance, azoxystrobin is labeled for both anthracnose and Microdochium patch, but has very little control on Microdochium in our region, so it’s not currently in my program. But if I get an infestation of summer patch or yellow patch, it can suddenly become invaluable.

A product that may work well for golf course ‘A’ may not be nearly as effective for golf course ‘B’ despite similarities in climate and turfgrass species.

Today there are more and more low-rate fungicides available. This is a trend that had to happen, and most plant protectant companies have realized this and focused their attentions in this area.

What diseases does it control?

I’m going to select fungicides that target the diseases I must deal with. For me, that is primarily Microdochium patch (fusarium for us but also known as pink snow mold in other parts of the country), anthracnose, summer patch, Waitea patch and yellow patch.

Although you may share your diseases with many other courses in your region, nobody is going to have your exact environment or situation. There are just too many factors involved that determine disease pressure and frequency. But it all starts with knowing the products that may be able to help you.

Another beneficial trend by manufacturing companies has been the influx of combination products. Examples include: azoxystrobin and propinconazole; chlorothalonil, fludioxonil and propiconzole; fluazinam and tebuconazole; PCNB and tebuconazole.

These are just a few of the combo products making many superintendents’ decisions a little easier.

Can I use it in my preventive program?

Again, it’s about finding fungicides that fit your program. It’s not only about fitting it for the diseases you have, but it’s also about being able to use it in your program and in your rotation. There are some great formulations that have come along that I simply cannot use on my property, in my program, at this time.

Which is not to say that some day I might actually switch to one or more of these. My fungicide program is annual. I examine it closely every year. You can’t be afraid to adapt and make changes.

Ron Furlong is the golf course superintendent at Avalon Golf Club in Burlington, Washington, and a frequent Golf Course Industry contributor.