Postharvest Practices to Minimize Decay in Apples
Chemical Control of Superficial Scald at Harvest
Diphenylamine (DPA). Use 1000 ppm for Rome Beauty and Winesap; use 2000 ppm for Red Delicious; use 2200 ppm for Granny Smith. The concentration of DPA to treat Fuji and Braeburn has not yet been determined.
Chemical Control of Blue and Gray Mold at Harvest
Thiabendazole (TBZ) sold in the Pacific Northwest as Mertect 340-F, Deccosalt 19, or Brogdex 594-F or 597-F. Only two applications of Mertect 340-F can be made to apples after harvest. Only 30 bins of apples may be treated with Deccosalt 19 per 100 gallons of liquid. Prior to application of Brogdex 594-F or 597-F, wash and rinse fruit and eliminate rinse water.
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Captan 50W at 2.5 lbs./100 gallons or Captan 80W at 1.6 lbs./100 gallons. Recharge suspension when water volume in tank is reduced by 25%, add 1.0 lb. of Captan 50W or 5/8 lb. of Captan 80W per 25 gallons water added. Dump tank after 8 hours of use.
Application of Fungicides in the Dump Tank
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SOPP. In immersion-type dumpers, use SOPP (Steri-Seal D or Stop Mold F) at 0.33% which is 1 gallon (22.5% a.i.)/100 gallons of water. Dip fruit for 30-120 seconds; rinse with fresh water after treatment; test SOPP concentration frequently; recharge when needed. Replace frequently; if the dump water is above 70°F, reduce concentration to 0.2-0.25%; if above 80°F, do not use SOPP.
If using SOPP, dump tank water may be sterilized with heat. Remove all fruit from tank, cover tank with Styrofoam or canvas, heat to 130°F and hold at that temperature for 25 minutes. Allow water to cool before dumping fruit into it. Ensure good building ventilation during heating. Approximately 10% water loss and 25% SOPP loss occurs during heating, requiring their replacement. Do not heat water containing chlorine.
Application of Fungicides on the Packingline
Thiabendazole (TBZ) sold in the Pacific Northwest as Mertect 340-F, Deccosalt 19, or Brogdex 594-F or 597-F. Only two applications of Mertect 340-F may be made to apples after harvest. Mertect cannot be added to wax; Deccosalt 19 can be added to wax.
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Captan 50W at 2.5 lbs./100 gallons or Captan 80W at 1.6 lbs./100 gallons. Recharge suspension when water volume in tank is reduced by 25%, add 1.0 lb. of Captan 50W or 5/8 lb. of Captan 80W per 25 gallons water added.
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Brogdex 360-F, a resin-based wax containing TBZ fungicide.
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Decco Apl Lustr-256, a shellac-based wax containing TBZ fungicide.
Dr. Eugene Kupferman, Postharvest Specialist
WSU Tree Fruit Research and Extension Center
1100 N. Western Ave., Wenatchee, WA 98801
Tree Fruit Postharvest Journal 4(1):8-9