Nematodes in residential lawns – best management practices
By Ralph E. Mitchell
Nematodes are practically everywhere in our Florida soils and most, believe it or not, are beneficial. Some of these microscopic worms are damaging to plants however, and can be a problem for our area lawns. They feed on grass roots causing decline and thin areas including yellowing, wilting and dead turf. What can be done to manage these micro-critters?
Microscopic worms, by their very nature, are not visible to the naked eye and work underground out of sight. They use needle-like mouthparts to puncture and feed on tender turf roots. Some feed on the outside of the root and some actually move right inside the root to feed. Common nematodes in Florida include sting, awl, stubby-root, root-knot and lance; just to name a few. Regardless, the feeding activity damages the roots so that they cannot function properly. The roots may be dark in color, rotten in appearance and even shortened. If nematodes were not stressful enough, environmental stresses such as drought can enhance the problem for grass. If nematode populations are high, grass may thin or die to the point where certain weeds such as spurge (a nematode indicator) take over the open, irregular patches. And since nematode damage looks like other turf problems, one must be careful to have a positive identification first. Suspicious samples can be submitted to the Florida Nematode Assay Lab for $20.00 to determine the nematode species and densities – please see the form and instructions here – http://nematology.ifas.ufl.edu/assaylab.
Different types of turf may either suffer or tolerate nematodes. Bahia grass, for example, is very tolerant of nematodes. St. Augustine grass is often affected by lance, sting, stubby-root, and root-knot nematodes. A popular cultivar of St. Augustine called ‘Floratam’ is noted however to be tolerant to sting nematodes. On the other hand, Zoysia grass is damaged quite equally by all of the nematodes just mentioned.
Some best management practices to help your turf deal with nematodes include simple cultural efforts such as proper irrigation and fertilization. Too much shade is also an environmental stress, so you may need to consider increasing the amount of light available by carefully thinning or trimming surrounding trees. The addition of organic amendments may also help the grass do better and may even introduce organisms that help suppress nematodes.
Often the last ditch effort in any Integrated Pest Management (IPM) program is the use of pesticides. There are some labeled for use on turf to suppress nematode populations. Some are even classified as bio-pesticides which use bacteria to protect turf roots. There may be other nematode products available as well. Please check the newly updated EDIS publication by Dr. Billy Crow, “Nematode management in Residential Lawns” at http://edis.ifas.ufl.edu/pdffiles/NG/NG03900.pdf for more details. As with any pesticides, please make sure to read the label as the label is the law. In some cases, check with Commercial Pesticide Applicators for this type of service.
Bottom-line, good cultural practices can help minimize the invisible scourge known as nematodes. Chemicals may be in our toolkit as well. New research is always coming up with improved developments, so be on the look-out for updates. For more information on all types of turf care information, please call our Master Gardener volunteers on the Plant Lifeline on Mondays, Wednesdays and Fridays from 1 to 4 pm at 764-4340 for gardening help and insight into their role as an Extension volunteer. Don’t forget to visit our other County Plant Clinics in the area. Please check this link for a complete list of site locations, dates and times – http://charlotte.ifas.ufl.edu/horticulture/Plant%20Clinics%20Schedule.pdf.
Crow, W. T. (2017) Nematode Management in Residential Lawns. The University of Florida Extension Service, IFAS.