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Re: [nafex] kaolin clay
This is a page from the May 19, '00 Apple Pest Management bulletin as issued
by Glen Koehler of the University of Maine Cooperative Extension (Pest
Management Office). Glen maintains a terrific IPM site and more that can be
accessed at > http://pmo.umext.maine.edu/apple/applpage.htm. Hope this helps.
> PESTICIDE NEWS
> Surround vs. bulk kaolin clay
> Surround is a registered EPA pesticide for use on
> apples that has also been cleared by the Organic Materials
> Review Institute. Applying a series of Surround sprays has
> been found to provide about 80% reduction of plum
> curculio damage compared to untreated trees. This is not
> quite as good as the 90+ % control achieved with the
> standard treatments of Imidan or Guthion, but it isn't far
> off. Surround may be seen as a supplement for existing
> controls, and may be sufficient as a replacement for
> organophosphate insecticides where there is moderate to
> low plum curculio pressure, or where the desire for
> organophosphate avoidance and/or organic certification
> outweighs the difference in efficacy.
> Surround seems to reduce tree stress from high temperatures and also to promote red fruit color
> development even from early season applications. Later season applications can prevent apple maggot
> damage. Surround is relatively benign on predators and is neutral on mites in that it does not reduce the
> mite population but does not cause mite population increase either.
> As with any material, there are requirements for effective use. Surround works as a barrier film.
> Excellent coverage is a must. For plum curculio, the first application should be made right at Petal Fall,
> with a follow-up application no more than a week later. It takes two applications to establish the level of
> residue and coverage required for full efficacy. Continued protection through the plum curculio
> immigration period would require reapplication at 7-10 day intervals. Because the Surround doesn't kill
> the plum curculio that encounter it, protection might be required for a longer period than the 3 to 5 week
> protection period required with organophosphate insecticide.
> The label for Surround states that the composition is 95% kaolin clay. Kaolin clay is sold in bulk
> form for many uses such as papermaking and pottery. Therefore, one might be inclined to think it is
> possible to save some money by purchasing cheaper bulk kaolin clay instead of paying for the same
> material labeled as Surround. However, the kaolin clay in Surround and the kaolin clay sold for other uses
> are really different materials using the same name.
> Here is some of what I learned from recent conversations with Dr. Michael Glenn of the USDA
> Agricultural Research Service, who recently received an award for being the lead scientist behind the
> development of Surround for use as an apple pesticide, and also with John Mosko the technical rep for
> the manufacturer:
> The kaolin clay in Surround has been highly processed through several manufacturing steps to
> achieve specific particle size, shape, density and texture that are much different from bulk kaolin clay.
> These attributes are essential to the way Surround functions.
> Efficacy: The finished product is hydrophilic instead of hydrophobic, and the mean particle size
> of Surround is much smaller than bulk kaolin clay, and just as importantly, the range of particle sizes is
> narrowed. Particle size makes all the difference in how the particles affect insects. Larger particles don't
> work. Surround has even shown promise as a suppressant against fire blight bacteria.
> Phytotoxicity: Researchers have investigated kaolin clay since the 1930s as a foliar spray
> material, and have always had to contend with phytotoxicity. Bulk kaolin clay particles reflect the
> photosynthetically active radiation (i.e. light) required by leaves to make food for the tree. Home-brew
> concoctions of bulk kaolin clay can and have caused serious phytotoxicity on tree fruit and vegetable
> crops by starving the foliage of light. By controlling size, shape and porosity of the particles, Surround
> particles allow light rays within the range needed for photosynthesis to scatter and bounce their way
> down to the foliar surface. Photosynthetic performance is not degraded, and by reflecting some of the
> other heat generating wavelengths, the plant's physiology can be enhanced rather than impaired.
> Residue: Surround is engineered for the right balance between retention to provide residual
> control, and depletion so that the coating even from late season applications is gone by the time fruit is
> harvested. Surround particle lay on the waxy fruit cuticle without becoming embedded in it. Bulk kaolin
> clay can become embedded into the cuticle making it difficult or impossible to remove.
> Formulation and coverage: Standard spreaders designed for apple pesticide tankmixes are
> designed to spread pesticides used at rates of no more than about 6 pounds of wettable powder or dry
> flowable per acre. Surround is applied to apple trees at rates of 25 to 75 pounds per acre. The sheer
> volume of dry material that is to be spread requires different surfactant characteristics.
> As in much of life, you get what you pay for, and the deal that sounds too good to be true
> probably is. The only good news about bulk kaolin as a spray material is that even though bulk kaolin
> does not have an EPA label, the Maine Board of Pesticides Control does not consider application to
> apple trees a violation if it is being used for non-pesticidal reasons. And that is about what you get with
> bulk kaolin clay: a non-pesticide that poses risk of phytotoxicity, irremovable residue, and maybe clogged
> nozzles thrown in for no extra charge.
> The Pesticides Control board does consider it clearly illegal for anyone to sell a material that does
> not have an EPA label, such as bulk kaolin clay, for use as a pesticide. Just because bulk kaolin clay is
> about as natural as you can get, that doesn't make it safe for plants or applicators. One of the main
> reasons for EPA registration is to prevent the sale of products that pose unreasonable hazard to crops
> and applicators.
> Glen W. Koehler, Associate Scientist IPM/NAPIAP
> Where brand names for chemicals are mentioned, no endorsement is implied nor is discrimination intended
> against products with similar ingredients. Consult pesticide product labels for rates, application instructions, and safety
> precautions. The label is the law. Disregard any statements in this newsletter if they appear to contradict label
> instructions. Users of pesticide products assume all associated risks.
> In complying with the letter and spirit of applicable laws and in pursuing its own goals of diversity, the University
> of Maine System shall not discriminate on the grounds of race, color, religion, sex, sexual orientation, national origin or
> citizenship status, age, disability, or veterans status in employment, education, and all other areas of the University.
> Questions and complaints about discrimination in any area of the University should be directed to the Director of Equal
> Employment Opportunity, 101 North Stevens, (207) 581-1226.
> I seem to recall a thread many months back on the use of kaolin clay
> as a pest deterrent on fruit trees. I searched the archives under
> kaolin but could not find anything. Any hints?
> kevin b
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