Golfdom, July 2017

Super Science Continued from page 33 1000 stunt nematodes per 100cc of soil should be a problem But it may not be depending upon the inherent health of the turf the depth of roots and management practices For this reason having a single number often is insufficient to determine if a green has a bona fide nematode problem Table 1 SAMPLING AND ALTERNATIVE PRODUCTS In a recent conversation a superintendent described how he once applied Nemacur fenamiphos on the approach side of a green based on nematode counts I forwarded to him from a declining area approximately 15000 stunt nematodes per 100cc of soil which is well over any established threshold The treated turf quickly perked up and looked better than it ever had The treated area looked so good he noted that members wondered if something was wrong with the untreated area The untreated area looked acceptable but had moderate nematode numbers that the superintendent decided not to treat because of the scarcity of Nemacur If both sides had been treated the green likely would have been in the best condition members had ever seen Prior to 2009 few superintendents undertook regular and repeated nematode sampling If nematodes were suspected and nematode counts were above threshold superintendents used Nemacur because it was widely available inexpensive and usually provided season long control In addition organophosphates like Nemacur work quickly when turf experiences genuine nematode induced symptoms A superintendent generally sees a dramatic improvement in turf quality three to five days after an organophosphate application if nematodes are a legitimate problem resulting in empirical evidence thats easy to demonstrate to members Although not labeled for turf nematodes superintendents who apply chlorpyrifos an organophosphate insecticide previously known as Dursban for annual bluegrass weevil also have managed to suppress nematode populations as a non target effect When an organophosphate application for nematodes has no effect on turf quality nematodes probably are below threshold The production of Nemacur was halted in 2009 Existing stocks were distributed and with the help of the Golf Course Superintendents Association of America superintendents have until Oct 6 2017 to use it up or legally dispose of it As an organophosphate Nemacur is extremely toxic and affects just about anything with a nervous system Approximately 200 mg of fenamiphos perhaps equivalent to a small ibuprofen pill would kill a 200 pound adult But it is an important and effective tool when used carefully and cautiously Its most significant drawback was its ability to migrate into sandy soils with the potential to contaminate drinking water in locations with shallow water tables Even careful use could not prevent it from migrating into these types of sensitive areas With the final cancellation of Nemacur superintendents battling nematodes need to find alternate nematicides Fortunately new products have been developed and show promising results but none are as effective as Nemacur They are however generally far safer to the environment and applicators than organophosphates and carbamates The new products are not without drawbacks and three primary issues have arisen with newer materials First some of them have a limited control spectrum A nematicide may work on one genus of nematode but not another Secondly the product may bind to thatch or get locked up in soils with high organic matter Finally the amount of nematicide required to achieve control may exceed what can practically be applied or it may cause damage to the turf when applied at high rates or inappropriately Before using any product superintendents should gather as much information as possible about their specific nematode problem SAMPLE ANALYSIS Superintendent usually count nematodes after extraction from the soil They sometimes are counted in the roots but our common thresholds are not calibrated for those types of counts and only lance or root knot enter the roots The soil extraction procedure typically uses a sugar solution to float nematodes out of soil The nematodes are lighter than the sugar solution while soil TABLE 1 Nematode Spring Threshold Severe Stress Stunt 800 1000 2000 3000 Lance 400 500 1000 2000 Spiral 2000 2500 4000 Ring 2000 3000 4000 Root knot 500 700 1000 Needle 100 200 500 Nematode thresholds vary considerably based on the species of grass being grown the time of the year management practices and soil composition The numbers presented below are typical guidelines we use to determine when nematode populations could be considered problematic based on a composite sample It should be noted that nematode populations increase throughout the season so a population at threshold in April will definitely be much higher in July if no attempt is made to control the nematodes 34 Golfdom July 2017 Golfdom com