2010 Annual Report 1a.Objectives (from AD-416) 1) Improve Pre-Plant Fumigation Strategies for Walnut Orchards (demonstrate the effectiveness of two MB independent alternatives.) 2) Predictive/diagnostic microbial detection technologies in evaluating MB alternatives. 1b.Approach (from AD-416) 1) Using six replications per treatment and plot sizes approximately 75'x160', the five treatments will be demonstrated and evaluated for effectiveness of managing soil-borne diseases in walnut. 2) Develop and use DNA arrays to detect pathogens as a function of soil fumigation treatments. Documents SCA with UC-Davis, Dept.Plant Sciences. 3.Progress Report Agreement was established in support of Obj. 1 of the in-house project, the goal being to demonstrate alternatives to MB in key crop systems and regions dependent upon MB. The goal of this project is to improve pre-plant fumigation strategies for walnut orchards and demonstrate the effectiveness of two MB independent alternatives. In Nov 2009 trunk caliper measurements were taken to compare treatment and rootstock growth effects. Tree row data could not be taken for comparison to 2008 data due to interference of the inter-row planted corn crop. The largest rootstock is Vlach (33.2 mm) followed closely by VX211 (31.0mm). The trees on paradox seedling were significantly smaller than the two clonal stocks (22.1mm). There presently are no significant differences in tree caliper size between the five fumigated treatments (average 32.4mm). However, the untreated trees are significantly smaller than those receiving fumigation (28.6mm). An oral presentation (abstract) was made at the Intl Methyl Bromide Alternatives Conference in San Diego, CA. In Dec 2009, a backhoe was commissioned to remove the dead and poorly performing trees. Each tree was sampled for nematode analysis. Each of the 36 plots was soil sampled for nematode analysis in 1 ft. increments to a depth of 5 ft. Each sample represented a composite of three locations next to the more susceptible paradox rootstock. Lesion nematode is still highest in the control treatment, but all the fumigated treatments except the Telone II in combination with chloropicrin are beginning to experience some infestation 750 days after treatment. In Jan 2010, the 2 yr-old, nursery grafted trees were replanted with the proper rootstock at every site. In mid-April, the experiment was pruned to insure optimal selection of lateral bud positions. Observations during the 2009 season indicated that the highly vigorous trees had “blind bud positions” in the 5-7 ft. zone of the trunk. These node positions failed to differentiate the lateral, dormant bud needed for proper future tree architecture. Therefore, we purposely delayed winter pruning to identify which bud positions would develop, and employed knife girdling above the still dormant nodes to encourage their growth. The trees were repeatedly walked and manipulated during leafout to maximize canopy development. Extensive tree mapping of the “blind bud” phenomena was also conducted, and it correlated with larger tree size. This may be a future horticultural problem associated with the highly vigorous clonal walnut rootstocks. The replant trees were tended with additional fertilizer and water to insure their maximum growth. Where possible, the replants were not headed back to 30", the standard practice for development of the trunk. They were instead left tall (6 ft.) from the nursery in an effort to develop the primary scaffolds this season. The objective is to have the replants as close in canopy size to the standard trees for harvest data 3 yrs. from now. The ADODR monitors this SCA by maintaining a complete file of the agreement, reviewing the annual reports, and conducting meetings with the cooperator during the course of the agreement.