[NAFEX] Calcium and Imidan

dmnorton at royaloakfarmorchard.com dmnorton at royaloakfarmorchard.com
Fri Jul 31 09:58:43 EDT 2009

According to Washington State University Crop Protection Guide for Tree Fruits, calcium chloride for apples is compatible with wettable powder formulations of azinphos methyl (Guthion), diazinon, phosmet (Imidan), and endosulfan (Thiodan).  This information is what we based our initial use of Calcium with Imidan on in past years.  BUT....what we have not mentioned is the Ph of the initial water going into the tank and the use of a buffering agent to adjust Ph. The buffering agents adjust the Ph of the tank mix to prevent the alkaline breakdown of the chemical formulation in water.  We have always had to adjust our water Ph before ANY spray or tank mix to the label recommendations of each product going into the tank.  Someone mentioned the use of vinegar in their spray mix, and a 1-cup  measure of cider vinegar to 100 gallons of water is a buffering rule of thumb to acceptably lower Ph.  Michael Phillips' book, The Apple Grower has a good section on this discussion and that is where I picked up on this information.  Michael participates in the Eco-Fruit Project in Wisconsin via conference calls each Monday morning for organic growers.  He reviewed this information last year during one of our calls.  Hope this answers your question!
Dennis Norton
Royal Oak Farm Orchard
Office (815) 648-4467
Mobile (815) 228-2174
Fax (609) 228-2174
  ----- Original Message ----- 
  From: Alan Haigh 
  To: nafex at lists.ibiblio.org 
  Sent: Friday, July 31, 2009 1:32 AM
  Subject: [NAFEX] Calcium and Imidan

  After seeing Dennis's response, I'm seriously doubting that my concern about mixing calcium and Imidan is legitimate.  I would expect that Dennis would have picked up on it if it was, as his grasp of chemical issues involving fruit production is substantial.

  So Dennis, I'm asking for your explanation of how you can safely mix calcium with Imidan without reducing the effectiveness of the Imidan?  Is the calcium formulated not to interact and affect the pH of the water in the mix?  I'm not very knowledgeable about chemistry.
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