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Gardening in Washington State

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Organic fungicides

Plant diseases caused by fungal pathogens are very common in home gardens in the Pacific Northwest, particularly west of the Cascade Mountains. Spring rains combine with warm temperatures and tender new plant growth to create ideal conditions for fungi to thrive and spread. Common fungal diseases seen in home gardens include powdery mildew, downy mildews, rusts, and late blight. Fortunately, there are many products available to home gardeners for managing diseases caused by fungal pathogens on plants. This fact sheet describes organic fungicides and provides information on:
• which organic fungicides are legal and available to home gardeners,
• how effective these organic fungicides are, and
• whether the products have unintended effects on people or the surrounding environment

Copper sulfate

More information is available on this free, downloadable fact sheet:

Submitted by: Linda Chalker-Scott, May 15, 2015

References for rubber mulch fact sheet

Arthur, M.A. and Y.T. Wang. 1999. Soil nutrients and microbial biomass following weed-control treatments in a Christmas tree plantation. Soil Science Society of America Journal, 63(3):629-637.

Azizian, M.F., P.O. Nelson, P. Thayumanavan and K.J. Williamson. 2001. Environmental impact of crumb rubber asphalt concrete leachate contaminants from highway construction and repair materials on surface and ground waters. American Chemical Society Abstracts 221(1-2): ENVR 15.

Bush, E., A. Owings and K. Leader, K. 2003. Foliar accumulation of zinc in tree species grown in hardwood bark media amended with crumb rubber. Journal of Plant Nutrition 26(7):1413-1425.

Bush, E., K. Leader and A. Owings. 2001. Foliar accumulation of zinc in tree species grown in pine bark media amended with crumb rubber. Journal of Plant Nutrition 24(3): 503-510.

Calkins, J.B., B.T. Swanson and D.L. Newman. 1996. Weed control strategies for field grown herbaceous perennials. Journal of Environmental Horticulture 14(4):221-227.

Chalker-Scott, L. 2007. Impact of mulches on landscape plants and the environment – a review. Journal of Environmental Horticulture 25(4): 239-249.

Christiansson, M., B. Stenberg and O. Holst. 2000. Toxic additives: A problem for microbial waste rubber desulphurization. Resource and Environmental Biotechnology 3(1): 11-21.

Ginsberg, G., B. Toal and T. Kurland. 2011. Benzothiazole toxicity assessment in support of synthetic turf field human health risk assessment. Journal of Toxicology and Environmental Health Part A 74(17):1175-1183.

Gualtieri, M., M. Milani, M. Camatini, M. Andrioletti and C. Vismara. 2005. Toxicity of tire debris leachates. Environment International 31(5): 723-730.

Kanematsu, M., A. Hayashi, M.S. Denison and T.M. Young. 2009. Characterization and potential environmental risks of leachate from shredded rubber mulches. Chemosphere 76(7):952-958.

Li,X.L., W. Berger, C. Musante and M.I. Mattina. 2010. Characterization of substances released from crumb rubber material used on artificial turf fields. Chemosphere 80(3):279-285.

Llompart, M., L. Sanchez-Prado, J. Pablo Lamas, C. Garcia-Jares, E. Roca and T. Dagnac. 2013. Hazardous organic chemicals in rubber recycled tire playgrounds and pavers. Chemosphere 90(2):423-31.

Ruffino, B., S. Fiore and M.C. Zanetti. 2013. Environmental-sanitary risk analysis procedure applied to artificial turf sports fields. Environmental Science and Pollution Research 20(7):4980-4992.

San-Miguel, G., G.D. Fowler and C.J. Sollars. 2002. The leaching of inorganic species from activated carbons produced from waste tyre rubber. Water Research 36(8): 1939-1946.

Simcox, N.J., A. Bracker, G. Ginsberg, B. Toal, B.Golembiewski, T. Kurland and C. Hedman. 2011. Synthetic turf field investigation in Connecticut. Journal of Toxicology and Environmental Health Part A 74(17):1133-1149.

Smolders, E. and F. Degryse. 2002. Fate and effect of zinc from tire debris in soil. Environmental Science and Technology 36(17): 3706-3710.

Snoddy, E.T. and A.G. Appel. 2013. Mulch preferences of the Asian cockroach (Dictyoptera: Blattellidae). Journal of Economic Entomology 106(1):322-328.

Solano, L., A.G. Ristvey, J.D. Lea-Cox and S.M. Cohan. 2012. Sequestering zinc from recycled crumb rubber in extensive green roof media. Ecological Engineering 47:284-290.

Steward, L.G., T.D Sydnor and B. Bishop. 2003. The ease of ignition of 13 landscape mulches. Journal of Arboriculture 29(6): 317-321.

Stokes, V. 2012. Some biodegradable mulch materials provide effective weed control during establishment of ash (Fraxinus excelsior L.) on farm woodland sites. Quarterly Journal of Forestry 106(4): 257-268.

U.S. Environmental Protection Agency (EPA). 2014. Common Wastes & Materials-Scrap Tires-Basic information.

Wik, A. and G. Dave. 2005. Environmental labeling of car tires – toxicity to Daphnia magna can be used as a screening method. Chemosphere 58(5): 645-651.


Gardening in Washington State, Puyallup Research and Extension Center

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