You Are Here: Management Updates 2009 Archive August 24, 2009

Date: August 24, 2009
Category: Nematodes
Subject: Damaging Namatode Populations

The UMass Extension Plant Diagnostic Lab has seen some unusually large nematode populations in golf course greens this summer. The symptoms of nematode injury are not specific like a patch disease, but are a general thinning and decline of turf. Particularly heavy infestations will result in wilt despite adequate moisture in the root zone. Nematodes are small (generally microscopic), non-segmented roundworms which are ubiquitous in all soils. Most nematode species feed on microscopic animals and plants like algae, fungi, bacteria, insects, and other nematodes.  Plant parasitic nematodes require a living host and are equipped with a specialized feeding structure, the stylet, which punctures plant cells and withdraws their nutrients.

The microenvironment of a golf course green is ideal for nematode growth and reproduction; the sandy texture, regular irrigation, and uniform presence of susceptible hosts facilitate nematode movement and population development. Nematodes are present in all turfgrasses, but damaging populations are present only on golf course greens.

Nematode populations tend to occur in clumped colonies in the top three to four inches of the soil. Populations from different cores of the same green will vary according to depth of the soil, depth of the root system, and depth of the accumulated sand from topdressing. Nematode populations in soil decline during the winter months and their reproductive potential increases as the soil warms. In New England, nematode populations generally peak from mid-June to late August.

Nematodes damage turfgrass roots by feeding on them or burrowing through root tissues. Symptoms on roots include swollen tips, galls, lesions, inhibition of root elongation, and short, stubby roots. Nematode populations are evaluated in context of species and numbers of nematodes present, depth of sample, depth of the root system, soil texture, species of turfgrass present, the occurrence of other stresses, and the extent of damage. The nematode population level which justifies the implementation of control measures is termed the threshold. Threshold levels are dependent on the variables already noted.

Presently, application of fenamiphos (Nemacur™) is the most effective method for controlling plant parasitic nematodes in turf. Nemacur™ is no longer available for purchase, but stockpiles of the material can be used. Nemacur™ provides protection immediately by preventing nematode feeding; it may require four weeks for nematode populations to decline. Research is underway at UMass by Dr. Robert Wick for effective alternatives to Nemacur for nematode control. Cultural practices that encourage healthy root system development including reductions of thatch and soil compaction, adequate nutrition and irrigation, and the temporary raising of mowing height are recommended as a first line of defense against nematode pressure. Healthy turf can withstand higher nematode populations than turf that is stressed.

Submitted by: M. Bess Dicklow

DISCLAIMER - As always, it is the responsibility of the applicator to verify the registration status of any pesticide BEFORE applying it. Different states have different regulations as well. The author and the University of Massachusetts are not liable for any consequences of any pesticide "recommendations". Mention of any trade name is not to be considered endorsement of a product.

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