[NAFEX] spray rainfastnest

Mark & Helen Angermayer hangermayer at isp.com
Mon May 26 14:27:51 EDT 2008


Several labels recommend spreader/stickers.  Rubigan fungicide, and Intrepid insecticide come to mind.  Other labels say that a sticker is not necessary but may be helpful.  Others, like Captan, say not to use a surfactant, as it could cause foliage burn.  Many labels also indicate the order to mix crop protectants, adding the sticker last.  Cornell may not mention adjuvants because it's assumed.  Sort of like adding a buffer to the water if the pH is above 7.  Most pesticides break down quickly in solution when the pH is high.  Captan is one of the worst.  If I recall the half-life is 2 minutes when the pH is above 9.  Imidan's half life is 8 minutes at 9 pH.  Our pH is 9.3, so I add a buffer most of the time, as well as a surfactant.


  ----- Original Message ----- 
  From: Alan Haigh 
  To: nafex at lists.ibiblio.org 
  Sent: Monday, May 26, 2008 11:49 AM
  Subject: [NAFEX] spray rainfastnest

  Dennis, I was aware of the systemic nature of S I and Strobe fungicides but I had never heard of your equation about wash off.  It's interesting and I wonder if you know what research it is based on.  Here Captan is partly recommended as a co-fungicide with the SIs because rain spreads it to leaves that grow out after spray.  

  I have never seen any research about the efficacy of spreader stickers when used with compounds designed to apply without them.  If they made a significant difference in reliability and staying power in regions that tend to get spring rain I'd expect their use would be recommended by Cornell.  There is no mention of their use in Cornell's tree-fruit spray guideline book and reducing pesticide volume is a major part of their mission.  We usually get rain between applications, often hard rain.  They only recommend their use when the label calls for it.  I have asked local commercial growers about this who agree that spreader-stickers are usually unnecessary and not helpful but I'm still open to new information especially if it transscends the anecdotal.

  My original question was actually primarily about how much drying time after an Imidan application is required before heavy rain because I assume that a certain amount of drying is needed to obtain significant rain-fastness. In that context I'm also curious about how much rain would remove a spray that hasn't dried.

  I am thankful for all advice including anecdotal but if anyone has research based info that would be especially appreciated.  I will contact Gowan tomorrow who manufactures Imidan and share with all any pertinent info.


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