TURF TIP
6/9/06

More on Nematodes and Indiana Greens

As our nematode survey continues, more questions are being asked about nematodes, their damage potential, etc. Following is an update on the survey:

  1.  Do not attribute all vague symptoms to nematodes. Nematode populations and symptoms are extremely complex and cannot be diagnosed by anyone other than a nematologist. In other words, don’t panic.
     All samples submitted so far have tested positive for some sort of turf parasitic nematodes, mostly Ring nematodes.
     Samples have tested as high as 2600 ring nematodes/100 ml of soil.
     In most case,s no visible symptoms are present, even on the over 2000 nematode/100 ml green, as few other stressing factors are present at this time.
     However, one green in Indianapolis may be showing symptoms of nematode damage, but this is very difficult to distinguish and isolate as the primary problem.
     Damage symptoms would include yellowing patches, thinning, enhanced drought stress, little or no response from fertilizer, and other symptoms reflective of a poor root system.
     Though thresholds are routinely published for determining control measures, these thresholds are complicated because symptom expression may be enhanced or complicated by poor rooting from summer weather, compaction, take-all patch, summer patch, natural decline of Poa annua, and other factors. That being said, following is a table of damaging thresholds from Nematode Parasites of Turfgrass, publication RPD No. 1108, from the Univ. of Illinois.
Damage thresholds for frequently encountered nematodes of turfgrasses in Illinois
Nematodes Nematodes/100c soila b
Lance 76+
Lesion 51+
Stunt 100+
Dagger 51+
Spirals 300+
Ring 300+
Pin 501+
a Combinations of nematodes, especially lance, lesion, and stunt, may cause problems at lower population densities.
b Eliminate pH, fertility, soil compaction, soil insects, diseases, etc., as possible factors limiting growth before using a nematicide.
  1.  We will try follow-up sampling on some of these greens during this summer.
     If symptoms are suspected, we do not recommend broadcast treatment. We’d first try a strip treatment or two of Nemacure. Effects on nematode numbers should be seen within 3-5 days. If successful, symptoms should start to decline within a week depending on growing conditions. The difficulty of applying Nemacure dictates that it should only be used in extreme cases.
     There’s an excellent source for nematode information entitled “Nematode Parasites of Turfgrass, publication RPD No. 1108” from the Univ. of Illinois at at http://web.aces.uiuc.edu/vista/pdf_pubs/1108.pdf
Jamal Faghihi, Nematologist
Zac Reicher, Professor/Turfgrass Extension Specialist

 

Send corrections, suggestions, and comments to biehlj@purdue.edu