Rapid Blight Cancel The title field is required!

1. Bywater Nigel

   
   7/6/2013 4:07 AM

   Hi all,
   
   Any of you guys have experience of dealing with Rapid Blight?
   
   I had it last year on some of my A4 greens and it would appear to be coming back again. I made a preventative application of Insignia two weeks ago thinking I was getting ahead of it but it didn't seem to work that well. I guess preventative program needs to start much earlier?
   Yesterday I made an application of Insignia with a small amount of Fore and I hope that will help to check it. I now plan to alternate between the two at around 10 to 15 day intervals.
   I have raised height of cut from 2.5mm to 3mm and I will raise again next week to 3.25mm.
   I am trying to keep my irrigation as lean as possible and hand watering where needed. Water quality isn't great with conductivity at 1525 and pH of 7.4. Water is from bore holes but I am on the coast so water is a little salty. The conductivity and pH are monitored on site each day but I will send samples to lab next week for a full check up.
   
   Any ideas will be gratefully received.
   
   Nigel Bywater
   Golf Course Manager
   Golf de Mogador
   Morocco

   
   
   
   
2. Larry Stowell

   

   0 posts
   
   7/6/2013 12:07 PM

   Nigel,
   
   Rapid blight is a high sodium/salinity induced disease. Your best management practice will be to maintain soil EC below 2 dS/m saturated paste extraction (same as mmhos/cm). You can monitor soil salinity using the Spectrum Technologies FieldScout EC meter (http://www.specmeters.com/nutrient-mana ... -ec-meter/). You will need to convert the FieldScout meter to a saturated paste extract - the direct meter reading target is 0.7 on the Field Scout (http://www.paceturf.org/PTRI/Documents/0303ref.pdf).
   
   To maintain low soil salts, periodic leaching will be needed to maintain low soil EC. It requires about 15 cm (6 inches) of water to drop soil EC by 50%. That is about 75,000 liters/465 m^2 (20,000 gal/5000 sq ft). Light frequent irrigation will deposit more salts at the surface of the green than deep and infrequent irrigation. Irrigating heavily when irrigating will prevent salts from accumulating.
   
   Sodium is the real issue, but sodium normally tracks closely with soil EC. The target to suppress rapid blight is less than 110 ppm Na using Mehlich-3 extraction. Leaching is the easiest way to reduce sodium, but sometimes additional calcium will be needed. If your water has residual sodium carbonate, you may need to apply gypsum or inject acid to help manage sodium.
   
   In addition to sodium increasing susceptibility to rapid blight, potassium has been shown to suppress the disease. We recommend targeting more than 110 ppm potassium using Mehlich-3 extraction to provide a little suppression.
   
   Summary:
   Monitor soil salts weekly and maintain soil salts below 2 dS/m - irrigation management is key - avoid light and frequent irrigation
   Maintain soil sodium below 110 ppm (leaching, gypsum)
   Maintain soil potassium above 110 ppm (don't go crazy stay at less than 150 ppm)
   Pyraclostrobin (Insignia) is the best product, rotate with Mancozeb - as you are already doing
   
   Background info:
   
   http://www.apsnet.org/publications/apsn ... light.aspx
   
   http://www.apsnet.org/edcenter/intropp/ ... light.aspx