Cooperative investigations of the ARS, USDA, and the Washington State University College of Agriculture and Home Economics Research Center, Prosser, WA 99350. Scientific Paper no. 7585. Mention of a trade mark or proprietary product does not constitute a guarantee or warranty of the product by the USDA and does not imply its approval to the exclusion of other products that may also be suitable. Results of research only are reported in this article.