2013 Annual Report
1a.Objectives (from AD-416):
Determine factors that influence the distribution and retention of Osmia lignaria bees following release in almond orchards, including locations of bee release and locations and density of artificial nest sites; determine relationship between bee nest site use and nut yield according to location.
1b.Approach (from AD-416):
Work will be performed during early spring in large (>100 acre) trial and commercial almond orchards in California over five years. In the first three years, research will be done in trial orchards, which will be pollinated with relatively small numbers of Osmia lignaria (8,000-20,000 per orchard) along with the standard number of honey bees (two hives per acre). In these orchards, cavities for use as O. lignaria nests will be deployed at various densities and patterns. Also, O. lignaria males and females will be released according to different management practices. Analyses of nest occupancy by bees will determine if placement of release location and availability of nests in different densities and locations influence the distribution and retention of bees in the orchards. Analyses of offspring size, number of offspring, and offspring sex ratio will be used to measure reproductive success under the various treatments. Data will be collected on the distribution of bees as indicated by occupied nests and also the yield of nuts in relationship to where bees nested throughout the orchards. Analyses will reveal effects of the distribution of nesting bees on nut yield.
In years 4&5, trial orchards will be exclusively pollinated by O. lignaria and the nest distribution experiment replicated. In addition, techniques based on previous years’ observations will be applied to counteract the tendency of the bees to nest preferentially in some areas and the consequent irregularity in pollination and hence nut yield.
In FY 2013, we analyzed data from the orchard experiments and wrote a manuscript evaluating the preference by Osmia lignaria for various nest box frequencies and number of cavities within nest boxes as well as the effect of releasing bees from one or 15 points within 4-hectare orchard sections. The manuscript on this work performed in 2012 is in the final stages of preparation for submission to Functional Ecology.