I believe the old warning against using exterior paints on tree trunks stemmed from the era when virtually all exterior paints were oil-based alkyd paints. The alkyd paints contained solvents and volatile organic compounds that could harm trunks, and the enamel alkyd paints may also have limited gas exchange through the bark during the period immediately after the paint was applied. So far as I know, exterior LATEX or water-based paints have not been shown to be toxic to trees, although the latex paints with a high acrylic content may still form a hard surface of cross-linked acrylic polymers that might have some negative effect on gas exchange. Thus, Win's comment about looking at the cheaper paints (which usually means less acrylic content because the high-acrylic content paints tend to be more expensive). I am not aware of any evidence that the fungicides in exterior paints would be toxic to tree trunks.
One rumored benefit of painting trunks is that painted trunks (especially on young trees) are less likely to be damaged by herbicides that contact the trunks. I am not aware of any research that supports this concept, although it may well be true. On Jul 14, 2013, at 11:25 AM, Win Cowgill <[email protected]<mailto:[email protected]>> wrote: Art- Stone fruit trunk spraying is primarily for Southwest Injury to the trunks. We also paint apples for the same reason but find that it also helps prevent rodent injury as well. In the past we have added Thiram technical to the apple mix to assist with rodent control but I no longer see an apple label for Thiram. Only the Chemtura Thiram has a NJ label for stone fruit. Thiram has been loosing its labels for years and is hard to find. - Make sure to check your state lables before using Thiram. On paint mixing, my guidance is always use the cheapest exterior white latex paint you can buy- the reason is the cheeper paint has the lowest acrylic content meaning less toxic to trees- I find the cheapest paint is usually the turf paint (used to paint lines on athletic fields) in 5 gallon pails. Shop around. We make a white wash of 60/40 water to paint and use a handgun sprayer with dedicated tank and roller pump to make the applications. You can adjust the ratio to make the right consistency to use in your sprayer. We also use the same tank setup for Borer trunk sprays on stone fruit. You want a nice white trunk and make sure to cover the lower branch/crotch's in stone fruit, they are most suceptable to winter injury. Win Cowgill Editor Horticultural News Professor and Area Fruit Agent New Jersey Agricultural Experiment Station Rutgers Cooperative Extension PO Box 2900 314 State Route 12, Bldg. 2 Flemington, NJ 08822-2900 Office 908-788-1339 Fax- 908-806-4735 Email: [email protected]<mailto:[email protected]> www.horticulturalnews.org/<http://www.horticulturalnews.org/> www.virtualorchard.net/<http://www.virtualorchard.net/> http://virtualorchard.net/njfruitfocus/index.html www.snyderfarm.rutgers.edu/investigators/cowgill.html<http://www.snyderfarm.rutgers.edu/investigators/cowgill.html> www.appletesters.net<http://www.appletesters.net/> <hortnewscover50percent.jpg> On Jul 14, 2013, at 8:45 AM, Arthur Kelly <[email protected]<mailto:[email protected]>> wrote: Does anyone know the recipe for trunk painting including joint compound? _______________________________________________ apple-crop mailing list [email protected]<mailto:[email protected]> http://virtualorchard.net/mailman/listinfo/apple-crop _______________________________________________ apple-crop mailing list [email protected]<mailto:[email protected]> http://virtualorchard.net/mailman/listinfo/apple-crop ************************************************************** Dave Rosenberger, Professor of Plant Pathology Cornell University's Hudson Valley Lab P.O. Box 727, Highland, NY 12528 Office: 845-691-7231 Fax: 845-691-2719 Cell: 845-594-3060 http://www.nysaes.cornell.edu/pp/faculty/rosenberger/
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