TURF MANAGEMENT: In nematode limbo

With Nemacur supplies depleting since the product went off the market in May 2008, golf course superintendents are searching for affordable alternatives to fight the parasitic worms that damage turf root systems, causing yellow blotches and dying patches of turf.

In 2002 the EPA determined that Nemacur, a Bayer product with the active ingredient fenamiphos, needed additional data to support the continued registration of the product. Bayer opted not to foot the bill to continue supporting registration. The EPA issued a 5-year phase-out of the product, permitting Bayer to sell Nemacur through May 2007, distributors to sell Nemacur through May 2008 and end-users to use the product until supplies run out.

And supplies are running out.

Tony Nysse took the job as superintendent at Pine Tree Golf Club last summer. With the sandy soils he has in Boynton Beach, Fla., Nysse knew he had to do something quickly to get the fairway nematode counts down to a manageable level. Unfortunately, the two or three leftover bags of Nemacur weren’t going to do the trick.

Based on nematode assays placing the sting counts in the 25 to 35 range, Nysse decided to use the soil fumigant Curfew on the TifSport bermudagrass fairways. Thankfully, Pine Tree’s former superintendent likely had made an application to the TifEagle greens the year before because all of the shortcut areas were within an acceptable range, though Nysse did use the remaining Nemacur on a few hotspots.

The Curfew fairway application was successful – post-application sting counts were down to the zero, 1 and 2 levels, Nysse says.

"It was a good kill, if you will," Nysse says of the application.

The application cost about $16,000 for 35 acres of fairways. Two tractors operated by certified Cerfew applicators covered Pine Tree’s fairways in four hours.

Thankfully, nematode counts in his shortcut areas were at acceptable levels, but that’s not likely to be the case in 2010. Nysse is budgeted to use Curfew there next season and possibly to apply Curfew in the fairways again, depending on the assay counts. All of that amounts to a pretty penny for his $2 million maintenance budget, of which $120,000 is designated to insect control.

"It’s pretty expensive, but once you have nematodes, there are not really a whole lot of options," he says. I don’t think Curfew is going to be the answer for every golf course out there. I don’t think a lot of courses can swallow a $20,000 application."

Such is the dilemma for many golf course superintendents these days. Since Nemacur has gone off the market, there are many products that claim to control nematodes, but few that do so affordably with the research to back them up.

Nysse, like many other superintendents, is looking into biological and botanical alternatives and has heard some success stories from peers. However, he’s waiting to see the research before committing to a more holistic solution to fight nematodes.

To find out the latest on nematode control product development, GCI spoke with Billy Crow, associate professor of nematology at the University of Florida in Gainsville.

In one respect, yes, and in one respect, no. From a safety and environmental standpoint, it was dangerous to work with. If not used properly you could have a lot of problems. And it’s been used for so long, there were a lot of issues where it wasn’t working very well – you’d have microbes building up that would eat the active ingredient.

With Nemacur going away, it’s prompted activity in research and development, and over next three to five years we’ll have a lot of new things coming on market.

There are synthetic nematicides that are getting better control than Nemacur; there’s a biological control product that will likely come out next year. Other than that, there will be a few years of lag time. Right now there’s a lot out there, but a lot of them aren’t that effective.

The company that’s developing some new actives, Divergents Inc., has a neat approach. They were looking more at genome mapping, and then they started developing very target-specific compounds so they’re very selective and they only affect parasitic nematodes, as opposed to Nemacur, which targets anything with a nerve system. These will be very safe products and we’re finding them to be very effective.

And then there are some that I can’t talk about at this time. But there are some new synthetic products we’ve had some good results with.

There will be a product launched this year called EcoNem, which is distributed by Harrell’s. It’s a bacterium that’s specific for sting nematodes. So there’s no efficacy except for sting nematodes, which are a problem in much of Florida and throughout the sandy coastal plains.

There’s the Bayer-purchased product I already talked about – they don’t have a name for it yet. It’s another bacteria. I’ve worked with it in the past with the company that was developing it and I did field trials with Bayer this year and had good results. They’re hoping to get it on market this year. In my trials I have specifically looked at the sting nematode with it. I haven’t looked for efficacy on other nematodes yet.

As far as biological go, that’s the one I’ve had best success with in getting nematode reductions and turf response.

You have to use biologicals differently than nematicides. You really need to apply them more prophylactically. Apply them early and prevent the problem from building up. If you wait until you have a big problem, it’s not going to work.

What are your thoughts on the various botanical products that are available to golf course superintendents, whether they’re based on sesame-seed oil, neem oil or other products?

As of this point we haven’t had success with botanicals in my research.

At this point we’ve got some long-term trials going; previously the longest we’ve run had been six months and we weren’t able to show reductions in nematode counts or improvements in turf. Maybe 18 months will prove better, but at least in the short term we haven’t had any nematode benefit.

Many of them have been moderately nematicidal in the lab, but the problem is getting them to the nematodes in the ground. They get diluted several hundred times when you irrigate on top of them.

There’s a black walnut oil-based product that’s being marketed for turf. It does kill nematodes if they’re exposed to it for three days, but in the field when you irrigate it gets leached and just doesn’t hang around. But some guys are using it and swearing by it.

And in California, there’s a nematode found on Poa on the crown of the grass. On that one, neem oil seems to be working pretty well.

So there are some exceptions.

In terms of enhancing plant tolerance, you can be looking at managing your fertility to avoid them. If you overdo nitrogen you get an overgrowing, succulent, tender root system that’s susceptible to attack by nematodes. You want roots to be growing, but hardening off as they grow. Some higher amounts of calcium, potassium and phosphorous can promote slower-growing, but hearty root systems that tolerate nematodes better.

And there are organic amendments – Milorganite and things like that. With repeat applications of these organic composts, sludges and manures, you can increase the nutrients and water-holding capacity of your soil. That can help in some situations. And in some cases you can stimulate microbial activity, which tends to suppress nematodes as well.

We’ve looked at microbial products like growth-promoting bacteria and biostimulants. Sometimes they seem to help, but not on a consistent basis.

I tell golf course superintendents if you want to try it it might help, but it’s hard to predict whether it will or not. But every once in a while you do get some improvement. It’s hard to tell exactly what happens.

I don’t tell people what to use, I give them the pluses and minuses. But here you go.

If you’re in a state where Curfew can be used, it’s highly efficacious. It’s far from ideal, but it works. Next year EcoNem will be on the market. I haven’t had real consistent results, but if you have a sting nematode problem, it would be worth giving it a try. It’s good in the lab, inconsistent in the field.

If the product Bayer has gets labeled soon, that’s given us some really good results. But other than that, none of these things out there have established consistent efficacy associated with them. Some of the microbial products, in some cases they’ve afforded some benefits.

And these things can be regional. For example, there are beneficial nematodes you can purchase for controlling grubs. Some research in the Midwest shows they may control plant-parasitic nematodes. Just because it doesn’t work in Florida, doesn’t mean it won’t work in Kansas or California or wherever. But remember, don’t believe everything you hear. As a nematologist, I hear some wacky things.

Marisa Palmieri is senior editor of Golf Course Industry.