Arboriculture & Urban Forestry 32(3): May 2006 105 signer) contains different active ingredients from the original film-forming polymers that are more stable and nontoxic to leaf tissue (Fuller et al. 2003). One important property of film-forming polymers is their ability to stretch during leaf expansion. Although not investigated in this experiment, greater stretching properties of Bond and Designer over Nu- Film-P and Spray Gard might as a result protect leaf surfaces for a longer period and in addition newly expanded leaf tis- sue, accounting for the marked degree of protection recorded (Sutherland and Walters 2002). Although the level of disease control achieved was statis- tically comparable with a currently used triazole-based fun- gicide, maximal reductions in disease severity against pow- dery mildew and Guignardia leaf blotch were obtained using penconazole fungicide sprays. In the case of the film-forming polymer Bond, disease severity of powdery mildew fell from 4.3 to 2.5 and Guignardia leaf blotch from 4.7 to 2.3. In the case of penconazole, disease severity of powdery mildew fell from 4.3 to 2.0 and Guignardia leaf blotch from 4.7 to 2.2. Such a result gives credence to the potential of film-forming polymers as an alternative or complement to conventional fungicides. Because film-forming polymers are biologically inert and act by physical means, they are not, at least in the United Kingdom, subject to the stringent legislative restric- tions relating to the use and application of conventional pes- ticides that act by chemical means. This also means that film-forming polymers can be used to control foliar diseases of urban trees for which no pesticides are registered. This would be of fundamental importance in the United Kingdom, where diseases such as anthracnose of willow (Marssonina salicicola (Bres.) Magnus) and London plane (Apiognomonia veneta (Sacc. et Speg. Hohnel), leaf spot of cherry (Blume- riella jaapii (Rehm) v. Arx.), and blossom wilt of cherry (Monilinia laxa (Aderh. and Ruhland) Honey) are increasing in severity on an annual basis, resulting in substantial mor- tality rates of infected trees. Likewise, film-forming polymers cost in general 40% to 80% less than conventional fungicides. Viewed in this context, the development of novel types of film-forming polymers may provide a useful addition to ex- isting methods of plant disease control. Acknowledgment. The authors are grate- ful for funding in part from the Tree Fund (Hyland Johns Grant). British Crop Protection Council. 2005. U.K. Pesticide Guide. Cabi Publishing, Oxford, U.K. Christiansen, E., P. Karokene, A.A. Berryman, V.R. Franc- eschi, T. Krekling, F. Lieutier, A. Lonneborg, and H. Solheim. 1999. Mechanical injury and fungal infection induce acquired resistance in Norway spruce. Tree Physi- ology 19:399–403. Elad, Y., N. Aynish, O. Ziv, and J. Katan. 1990. Control of grey mould (Botrvtis cinerea) with film-forming poly- mers. Plant Pathology 39:249–254. Elad, Y., O. Ziv, N. Aynish, and J. Katan. 1989. The effect of film-forming polymers on powdery mildew of cucumber. Phytoparasitica 17:279–288. Fuller, M.P., F. Hamed, M. Wisniewski, and D.M. Glenn. 2003. Protection of plants from frost using hydrophobic particle film and acrylic polymer. Annals of Applied Bi- ology 143:93–97. Gale, J., and R.M. Hagan. 1996. Plant antitranspirants. An- nual Review of Plant Physiology 17:269–282. Gale, J., and A. Poljakoff-Mayber. 1962. Prophylactic effect of a plant antitranspirant. Phytopathology 52:715–717. Haldimann, P., and R.J. Strasser. 1999. Effects of anaerobio- sis as probed by the polyphasic chlorophyll and fluores- cence rise kinetic in pea (Pisum sativum L.). Photosyn- thesis Research 62:67–83. Han, J. 1990. Use of antitranspirant epidermal coatings for plant protection in China. Plant Disease 74:263–266. Hibbard, J.M., P. Richardson, and R. Whitbread. 1996. Ef- fects of leaf age, basal meristem and infection with pow- dery mildew on photosynthesis in barley grown in 700 mol mol–1 CO2. New Phytologist 134:317–325. Hodge, S.J. 1991. Urban Trees; a Survey of Street Trees in England. Forestry Commission Bulletin 99, HMSO, Lon- don, U.K. Lichtenthaler, H.K., and A.R. Wellburn. 1983. Determina- tions of total carotenoids and chlorophylls a and b of leaf extracts in different solvents. Biochemical Society Tran- scripts 11:591–593. Marco, S., O. Ziv, and R. Cohen. 1994. Suppression of pow- dery mildew in squash by applications of whitewash, clay and antitranspirant materials. Phytoparasitica 22:19–29. Maxwell, K., and G.N. Johnson. 2001. Chlorophyll fluores- cence: A practical guide. Journal of Experimental Botany 51:659–668. LITERATURE CITED Agrios, G.N. 2004. Plant Pathology, 5th ed. Academic Press, San Diego, CA. Backman, P.A. 1978. Fungicide formulation: Relationship to biological activity. Annual Review of Phytopathology 16: 211–237. Osswald, W., M. Niehuss, W. Huber, and E.F. Elstner. 1984. Support of non-host resistance by artificial leaf coating. Journal of Plant Disease Protection 91:337–344. Percival, G.C. 2001. Induction of systemic acquired disease resistance in plants: potential implications for disease management in urban forestry. Journal of Arboriculture 27(4):181–193. ———. 2004. Evaluation of physiological tests as predictors ©2006 International Society of Arboriculture
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