A new nematicide for turfgrass

A byproduct of sugar processing has shown some efficacy as a nematicide in turfgrass.

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A Multiguard Protect-treated plot shows turf improvement
after three applications.
Photo by W.T. Crow

William T. Crow, Ph.D.

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A few years ago a new turfgrass nematicide, Multiguard Protect EC (furfural, Agriguard) came on the market in the United States. The active ingredient in Multiguard Protect is furfural, which is a byproduct of sugar processing. Furfural has a number of industrial uses including being an industrial solvent, and in some cases, a food additive. The activity of furfural against nematodes was first recognized a couple of decades ago, but because it has limited solubility in water, its practicality as a nematicide was limited. Illovo Sugar in South Africa is the world’s largest producer of high-quality furfural. Their chemists began searching for new uses for furfural and came across the earlier reports of its nematicidal effects. They then developed emulsifiable formulations of furfural that disperse in water and are well-suited for soil applications. Illovo has now developed several furfural-based nematicides, including CropGuard and Protect in South Africa and Multiguard Protect in the United States.

University of Florida research

Although Multiguard Protect is new to the market, at the University of Florida we have been working with Illovo formulations of furfural for more than 10 years. In the laboratory and greenhouse, we have conducted doseresponse and exposure-time experiments with Multiguard Protect to determine the concentrations and exposure times required to incapacitate sting nematode (Belonolaimus longicaudatus), the most damaging nematode on turfgrasses, and several other turf nematodes  (root-knot [Meloidogyne graminis], ring [Mesocriconema ornatum], and spiral [Helicotylenchus pseudorobustus] nematodes). We have conducted numerous field trials with Multiguard Protect, evaluating effects on nematodes and on turf health of different rates, application timings and application methods. Our field trials have been conducted in a variety of environmental conditions, including the University of Florida Plant Research and Education Unit (PSREU) at Citra, Fla., and at golf courses in the area, on multiple warmseason turf cultivars and species, and different kinds of nematodes. This paper will give an overview of Multiguard Protect, summarize our research results and outline how best to use the product based on our current knowledge about it.

Results and discussion

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Figure 1. Effects of increasing concentration of Multiguard Protect in soil solution on number of healthy sting nematodes recovered three days after treatment in a laboratory experiment.

Furfural is a contact nematicide, meaning that it affects nematodes in the soil, but not those that are inside plant roots. Therefore, in most cases, Multiguard will be more effective against ectoparasites like sting nematodes than it is against endoparasites like lance nematodes. Multiguard is not unique in this respect. Other than Nemacur (which will not be permitted for use on golf courses as of Oct. 6, 2014), none of the turfgrass nematicides currently on the market has systemic activity. However, even endoparasites will spend time in the soil when they can be affected by contact nematicides like Multiguard.

Like most pesticides, the higher the concentration of furfural in soil solution, the better it works (2) (Figure 1). Unfortunately, as rates get higher, the risk of phytotoxicity to turf also increases. The current maximum labeled rate of 8 gallons/acre (74.83 liters/hectare) is on the low side with regard to efficacy, but has less potential for negative effects on turf than higher rates. This means that single applications of Multiguard are typically insufficient and, in most cases, several applications are required to reduce nematode numbers in soil and improve turf health. In our field trials, we usually do not start observing results until after the second or third application. A single application will kill some, but not most, of the nematodes present. Based on our research results, a sequence of applications made at twoto three-week intervals will maximize effects on nematodes while minimizing the potential for phytotoxicity. Application intervals of greater than four weeks are usually too long and allow nematode populations time to recover between applications.

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Figure 2. Effects of increasing exposure time to Multiguard Protect (at 1,500 parts per million in soil solution) on the number of healthy sting nematodes in a laboratory experiment.

Maximum effects to nematodes are realized after 18 to 24 hours of exposure to Multiguard (2) (Figure 2). Therefore, after an initial post-application irrigation with ¼-inch (0.635 centimeter) of water, we recommend not irrigating again until 24 hours have passed. This will allow maximum exposure of the nematodes to the furfural in soil solution. We also do not recommend applying Multiguard Protect if there is a high risk of substantial rainfall in the 24-hour forecast.

We have conducted numerous field trials with Multiguard Protect on nematode-infested bermudagrass (Cynodon species) greens. In most of these trials, we have observed turf improvement after two or three applications (1) (Figure 3). This improvement was greatest from spring and fall applications and not from summer applications. Therefore, for best results in Florida, we recommend applying Multiguard sequences in spring and/or fall. This recommendation may be different for other regions.

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Figure 3. Effects of three spring applications of Multiguard Protect on the percent of turf green cover of (A) Tifdwarf, (B) Jones Dwarf and (C) Champion bermudagrass greens in Citra, Fla. Stars indicate application dates. Asterisks (*, **, ***) indicate values that are significantly different from the untreated plots at P ≤ 0.1, 0.05 and 0.01, respectively.

One of the mysteries about Multiguard was that often in our field trials, even when we observed turf improvement, we were not able to observe significant reductions in nematode counts. For example, in the three trials shown in Figure 3, we observed no significant nematode reductions despite having significant turf improvement. Therefore, we conducted additional trials on bermudagrass tees, studying the effects of Multiguard Protect on numbers of sting nematodes at different soil depths. Some of the results from these trials are shown in Figure 4. In the top 2 inches (5 centimeters) of the soil profile, Multiguard was not effective against sting nematodes. However, at depths of 2 to 4 inches (5 to 10 centimeters) and 4 to 6 inches (10 to 15 centimeters) (data not shown), Multiguard reduced numbers of sting nematodes after two applications of the maximum labeled rate (1). These results indicate that Multiguard Protect is effective against sting nematodes, but not in the top 2 inches of soil.

We know that furfural is rapidly broken down by soil microbes, particularly in aerobic conditions. Therefore, we hypothesize that because the top portion of the soil profile has high microbial activity and aerobic conditions, the furfural gets broken down too quickly in that area to have the desired effects. In lower portions of the soil profile, where less oxygen is available and microbial activity is lower, the furfural should stay around longer and have greater impact on nematodes. The reason that we were unable to observe significant nematode reductions in many of our earlier trials is likely because we typically sample to a depth of 4 inches, which includes the ineffective zone. This likely dilutes the overall observable effects.

Conclusions

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Figure 4. Effects of three applications of Multiguard Protect at two-week intervals on the number of sting nematodes at depths of 0-2 inches (A) and 2-4 inches (B) of soil profile on bermudagrass golf tees at Palatka and Citra, Fla. Stars indicate application dates. Asterisks (*, **, ***) indicate values that are different from the untreated plots at P ≤ 0.1, 0.05 and 0.01, respectively.

In summary, Multiguard Protect is an effective management tool for nematodes on turf, particularly ectoparasitic species like sting nematode. However, it must be used correctly in order to be effective. Before treatment, the soil must be moist to prevent phytotoxicity, so superintendents should pre-irrigate if necessary. After application, irrigating immediately with ¼ inch of water will move the furfural into the soil profile. After wateringin the treatment, do not irrigate again for 24 hours. Make multiple applications at two- to four-week intervals.

Although it is helpful, Multiguard Protect is not a silver bullet against nematodes (we do not know of any product that is), and expectations should be realistic. We observe improved turf health while the Multiguard application sequence is ongoing, but usually these are not long-term benefits. Multiguard will suppress nematodes, but it will not make all of them go away. For these reasons, Multiguard will typically work best in rotation or in combination with other nematode management tools in a nematode IPM program and only rarely should be relied on as a sole tactic against nematodes. Multiguard works better against some nematodes than others, and better on some courses than others. We have also observed differences in sensitivity among grass species and cultivars. Therefore, before treating large areas, the golf course staff should first do some trial testing to familiarize themselves with the product and its effects on their grass and in their environment.

Acknowledgments

Funding for these studies was provided by Illovo Sugar and Agriguard Co. The author also would like to thank Mark Kann and his staff at the University of Florida Plant Science Research and Education Center in Citra, Fla., and the superintendents and staff of the many cooperating golf courses.

Literature cited

  1. Crow, W.T., and J.E. Luc. 2014. Field efficacy of furfural as a nematicide on turf. Journal of Nematology 46:8-11.
  2. Luc, J.E., and W.T. Crow. 2013. Factors affecting furfural as a nematicide on turf. Journal of Nematology 45:260-264.

William T. Crow, Ph.D., is a professor and landscape nematologist in the entomology and nematology department at the University of Florida, Gainesville, Fla.