Cheadle Center for Biodiversity and Ecological Restoration

In 2010, we initiated research on pollinator habitat gardens (hedgerows) in 8 stone fruitorchards in Brentwood, in northern California. One goal was to install native and non-native plant speciesin linear gardens to attract native bee species, which we used successfully statewide (Frankie et al., 2005,2009, 2014). Our 2010-2018 Brentwood research demonstrated that planned hedgerows attracted diversenative bee taxa (144 species), and that many species (23) also visited a variety of crop flowers (Frankieet al., 2018). In our current study, we applied these past experiences to avocado orchards in southernCalifornia to examine avocado flower visitors in installed habitat gardens, or hedgerows. Gardens wereinstalled in 3 avocado orchards in Santa Barbara and Ventura Counties to evaluate native bee diversityand abundance between hedgerows (treatment sites) and surrounding orchards and wildlands (controlsites). Native bees and Western honey bees (Apis mellifera) were monitored at each orchard over 6 yearsfrom 2014-2019, with supplemental collections done in 2020-2021. Hedgerow sites had greater beespecies diversity, and slightly greater bee abundance. At the 3 orchards, 105 bee taxa were recorded fromstandardized monitoring periods during avocado flowering season (March-May). Honey bees were foundto visit many hedgerow plants, and avocado growers indicated the importance of having floral resourcesyear-round for the bees. ‘Lisbon’ lemons are often grown in close proximity to avocado trees, and controlof Citrus pests, especially the Asian citrus psyllid, was factored into variables impacting avocado visitors.At least 60 insect taxa were recorded visiting avocado flowers. Half of these were native bee taxa, and therest were flies (especially syrphids), wasps, and beetles. Factors impacting long-term bee monitoring resultsincluded unusual weather conditions, wildfires, and possible pesticide drift. Frequent communication withgrowers was critical for sharing findings, collaborating in plant installations, and addressing questions.