2009 Annual Report 1a.Objectives (from AD-416) This research program seeks to identify and implement methods, which are compatible with organic production systems, for the control of disease phenomena that are biologically complex. Our goal is to develop a management program that ensures successful establishment of new fruit trees on old orchard sites and sustains productivity of these orchards through maximizing the efficiency of the biological resources resident to the orchard soil ecosystem. 1b.Approach (from AD-416) A composite brassicaceous seed meal in concert with use of a disease tolerant apple rootstock will be evaluated as an alternative to soil fumigation for control of apple replant disease in field trials. The impact of seed meal particle size on generation of biologically active chemistries (allyl-isothiocyanate) from Brassica juncea seed meal soil amendment, and composition of the resident soil microbial community contributing to disease suppression. The effect of different brassicaceae seed meals or composite seed meal amendments on composition and activity of resident soil fauna communities involved in N mineralization will be determined. The use of a composite seed meal to decrease rates nitrification and thus minimize N loss resulting from leaching will be assessed. Documents Reimbursable with CSREES. Log 35377. 3.Progress Report This project relates to objective 1 of the associated in-house project, which seeks to determine the relative contribution of chemistry and soil biology to the control of soil borne diseases that is realized through soil incorporation of mustard plant residues. During FY2009 the effect of mustard seed meal particle size on production of a volatile antipathogen compound and suppression of different plant pathogens was evaluated. Particle size had a significant impact on the level of the volatile compound that was generated in response to soil application of mustard seed meal with small particle size aways yielding a higher maximal volatile concentration. In addition, the total cumulative volatile compound yield was also significantly higher in soils receiving the fine particle amendment. This is an important finding as for certain soilborne pathogens, generation of this volatile compound is the dominant mechanism contributing to disease control. Evaluations in the laboratory indicate pathogen growth is reduced more if exposed to soil amended with fine rather than coarse particle mustard seed meal. These initial findings indicate that field application of mustard seed meal for control of soilborne pathogens will necessitate the use of the appropriate sized particles in order to obtain the optimal level of disease suppression. Monitoring Activities: Progress is monitored through annual submission of written progress report.