Nematicides for Established Commercial Turf

Only one chemical nematicide is currently available for use on established turfgrass stands. It is an organophosphate, namely fenamiphos (Nemacur 10G or 3 EC). However, Nemacur is being withdrawn from the market and only existing stocks may be used. This material can only be used on commercial  turf (including golf courses, cemeteries and industrial grounds) where the risks of exposure can be minimized. The active ingredient in the granules or emulsifiable concentrate must be carried into the soil by an adequate amount of irrigation or rain water (enough to reach the root zones and give effective control of nematodes but without product loss through leaching). Nemacur can no longer be sold after November 2008 but material in stock can still be utilized indefinitely.

Nematicide applications should be made in autumn or spring (before nematode populations peak) during periods when soil temperatures are above 60ºF according to the product label. For granular formulations, gravity or “drop-type” granule spreaders are preferred (or required) over centrifugal types for more accurate application and for ensuring the safety of animals, humans and non-target plants.  Experiments comparing the effectiveness of broadcast application of granules vs. subsurface injection of granules have shown similar effectiveness.  Subsurface injection in fairways is practical and should reduce the potential for off-site movement of material.

Prior to application, physical soil treatments that aid soil penetration by water (such as core cultivation, vertical mowing and mechanical thatch removal) may aid in effectiveness. Applications should be followed by adequate overhead irrigation in order to wash the active ingredient into the soil and avoid exposure of people, pets and wildlife to the chemical.

The following rules are required for fenamiphos use. These measures are designed to reduce the risk of exposure to birds and aquatic organisms. It is suggested that others consider adopting these guidelines as good stewards of the environment as well as for the product. No more than 10 acres per golf course per day may be treated with Nemacur (3 EC or 10G). There must be a three-day interval before an additional 10 acres could be treated. Do not apply Nemacur closer than 10 feet from bodies of water and surface fairway drains. Total product application must not exceed 200 lb per acre per year.  

At this juncture, instructions for the use of Nemacur remain the same as stated on the most current product label for other states in the Southeast. The safest guidelines are always on the product label. The product must be distributed evenly over the area to be treated and it must be washed immediately into the soil with at least 0.5 inches of water (usually up to the point when 1 inch of the top soil has become wet). Total irrigation should not result in puddling and runoff. Do not apply Nemacur where water runoff is likely to occur. The 3 EC formulation is not recommended for use on greens and tees. The purchase and use of all formulations of Nemacur are restricted to certified applicators for uses authorized by their certification, or to persons under their direct supervision. 

The effects of nematicides are only temporary.  Fumigants leave behind no residual active ingredients, so nematodes that survived the treatment (i.e., were too deep to be reached by it) or were brought in on the new sod can begin to re-colonize the normal turf root-zone immediately.  The non-fumigant nematicides that may be applied to living turf must remain in the root-zone (top 4-10 inches in which most turfgrass roots normally grow) for several weeks to be effective.  However, they will eventually dissipate from that region as a result of combined effects of leaching and decomposition.  These products do not necessarily kill all nematodes that are exposed to them, but "inactivate" or paralyze many of them.  Therefore, when the chemical is gone, there are usually some nematodes ready to resume feeding and reproducing.  With either kind of nematicide, the treatment only provides a limited period of relief from nematode stress.  The treatment cannot result in the desired improvement in turf health unless other stresses are also controlled and the nutrients (especially potassium) and water that are needed for good root growth are available.

Over-Use of Nematicides

No nematicide is equally effective against all nematodes.  When one is used frequently, nematodes that are least affected by it will have a distinct advantage over those that are most affected by it.  For instance, prolonged frequent use of a product that affects lance nematodes less than other species enables lance nematodes to become dominant in that population.  We believe that this has happened with Mocap in some cases, at least in part because Mocap is not systemic (absorbed into the live root tissues) and therefore cannot reach endoparasitic nematodes that are living inside those roots.

Enhanced biodegradation is a phenomenon that can reduce the effectiveness of soil-applied pesticides where the same product has been used over a prolonged period of time.  Repeated application of the same chemical to soil encourages build-up of bacteria and other microbes which can metabolize ("digest") that chemical, so they can destroy it much more quickly than was the original case.  The net effect is a shorter period of control from a given treatment.  Enhanced microbial degradation has been reported for over 200 soil-applied pesticides, including nematicides, which have been used too frequently on a particular site.   Enhanced biodegradation of Nemacur has been documented in South Carolina recently on several golf courses experiencing chronic problems with nematode control.  Therefore, it is prudent to use all soil pesticides as little as necessary, to reduce chances of developing such soil microbial populations.  It also seems wise to rotate or alternate among all products that are legal and effective for a particular problem, to avoid prolonged selection for microbes that can build up on a particular pesticide.