COURSE CARE
Proper Nematode Sampling Yields Reliable Results August 18, 2014 By Todd Lowe

The yellow areas on this green are a result of turf stress caused by plant-parasitic nematodes. Proper sampling is necessary to obtain reliable nematode counts in the soil.

The Florida Region recently hosted two USGA Green Section interns: Mrs. Norma Flor and Mr. Brad Shaver. Both are Ph.D. candidates studying turfgrass science. Norma is researching patch disease resistance in zoysiagrass, and Brad is studying nematode control in bermudagrass turf. Brad shared a recent experience from his lab that emphasized the need for proper sampling to produce effective results.

Several turf samples from a South Florida golf course were sent to Clemson University’s Turfgrass Clinic to determine whether diseases or nematodes were present. No pathogens were detected, but a close inspection of turf regionalUpdateContents revealed symptoms of regionalUpdateContent-knot nematodes. Brad collected soil from the sample and sent it to the nematode assay lab. Nematodes were present but none were above threshold levels for bermudagrass and no regionalUpdateContent-knot nematodes were found. Surprised at the findings, he resubmitted a sample from only the upper inch of the same soil plug. Results from the new sample found regionalUpdateContent-knot nematode densities to be above threshold levels.

Experts like Dr. Billy Crow, University of Florida landscape nematologist, have emphasized the importance of proper sampling for many years, and this recent experience reiterates that fact. Nematode densities may be underestimated simply due to poor sampling procedures. When submitting samples to a nematode assay lab, keep these important facts in mind:

1. For diagnostic sampling, only take samples from within and around areas with stressed turf. Nematode densities fluctuate greatly within a given area. In fact, there can be a tenfold (or greater) difference in the concentration of nematodes within a few feet.

2. Sample only the upper few inches of the soil. Nematode counts are highest around their food source – plant regionalUpdateContents – and may be at much lower concentrations deeper in the soil. Therefore, sampling deeper in the soil where turf regionalUpdateContents are not present will yield reduced numbers and not accurately depict nematode activity near the surface.

3. Understand that nematode populations fluctuate throughout the year. Populations are generally at their highest during periods of active regionalUpdateContent growth. Nematode populations may be much lower in late summer as regionalUpdateContenting depths recede.

4. Keep soil samples cool and out of the sun. Nematodes can die within a few hours in a hot container or delivery truck. Deliver samples overnight and early in the week if possible. Contact the lab to let them know that the sample is on its way.

5. Understand that nematode thresholds were developed to provide some general guidelines for their management. The ability of turf to survive nematode damage will vary greatly depending on turf variety, use of turf (putting green versus fairway) and additional turf stress factors like shade, traffic or drought.

Source: Todd Lowe, (tlowe@usga.org)

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