) production and the company recently partnered with Driscoll\u2019s. Beeflow\u2019s strategy is to \u201ctrain\u201d honey bees to forage on target crops, even if they naturally tend to be less attractive to honey bees, and to do this across a wider temperature range. They accomplish this through provision of a supplement that \u201ctrains\u201d honey bees to forage on the target crop using odorant mixtures that contain floral scents of the target crop. According to Beeflow, the supplement also supports bee immunity and nutrition. The strategy has scientific merit (Arenas et al., 2007; Balbuena et al., 2012; Farina et al., 2022; Negri et al., 2017) and preliminary results have been promising. According to Stine (2019), Beeflow\u2019s technology has led to a seven-fold increase in bee activity in California\u2019s Central Valley at temperatures below 55 \u00b0F.\u00a0\u00a0<\/span><\/p>\n\n\n\nThe initial success of the Beeflow technology warrants further investigation. The objective of this study was to assess the impacts of Beeflow technology on honey bee activity and crop pollination in highbush blueberry systems in northwestern Washington. <\/span><\/p>\n\n\n\nApproach<\/span>:<\/h2>\n\n\n\nAssessments of Beeflow technology were done over two years (2021 and 2022). In 2021, we established a paired design experiment with the main treatment factor being the presence or absence of Beeflow technology. A hive-applied feed was the primary variable that was different between treated and untreated sites with the feed applied approximately two weeks before placement in treated blueberry fields and repeated every two weeks by the beekeeper or Beeflow team. Treated sites also had beehives placed in a distributed configuration with pallets of beehives adjacent to the field edge. Untreated sites did not manipulate placement location of beehives. <\/span><\/p>\n\n\n\nTreatments in 2021 were replicated across three field sites each (n=6 sites total; 4 \u2018Duke\u2019 and 2 \u2018Last Call\u2019) all stocked at 4-6 hives\/acre of honey bees. Unfortunately, the \u2018Last Call\u2019 pair was dropped because the Beeflow treatment could not be successfully implemented with our beekeeper cooperator. Remaining sites were all conventionally managed, had the same grower within a pair, and were located in Skagit and Whatcom counties of northwest Washington. Hives were placed in the study sites at approximately 5-10% bloom. To maintain independence, each site was a minimum of 2 miles apart and all had the same beekeeper (Belleville Bees) to minimize beekeeper variation. All plants were established and approximately the same age (6 years or older).\u202f<\/span> <\/span><\/p>\n\n\n\nHoney bee foraging (i.e., flower visitation) data were collected weekly on suboptimal and optimal pollination days (temps >55 \u00b0F) to evaluate Beeflow\u2019s effect on honey bee activity across environmental conditions. Honey bee foraging was assessed within three, 328-ft-long transects per field with transects starting 30 ft from the field edge and located approximately in the geometric center of the field in order to get an estimate of average pollination conditions. Honey bees foraging data were recorded by slowly walking down a transect (i.e., row) and counting the number of honey bees feeding from open blueberry flowers on a half-bush basis.<\/span> <\/span><\/p>\n\n\n\nHoney bee colony strength was also measured using a non-invasive return forager method whereby the number of honey bees returning to their colony are counted within a 1-minute period (Sagili and Burgett, 2011). Return forager counts were measured from four randomly selected hives per field at the beginning and end of bloom. All honey bee data were collected between 10 am \u2013 4 pm. Each field was visited a minimum of three times, with some fields being visited four times during the bloom window. <\/span> <\/span><\/p>\n\n\n\nWithin each transect, three bushes were labeled with flagging tape and flowers were counted from one labeled and representative branch at mid-canopy level per bush. Flowers on labeled branches were counted twice during bloom. Flower counts were later used to determine percent fruit set [i.e., (# blue fruits \u00f7 # flowers) x 100] from each branch. Average berry weight was measured from fully ripe blueberries collected from our labeled branches shortly before commercial harvest. <\/span> <\/span><\/p>\n\n\n\nIn 2022, another paired design experiment was established and conducted in northwest Washington. However, \u2018Liberty\u2019 was used instead of \u2018Duke\u2019 and one site was only 0.6 miles away from another field site instead of 2 miles. All data were collected using the same protocols implemented in 2021 with a few exceptions. In 2022, three branches were labeled per bush and assigned one of three sub-treatments: 1) Bagged = pollinators excluded\/negative control; 2) Hand pollinated = full pollination\/positive control; and 3) Open pollinated = natural field-level pollination. This method can be used to assess whether pollination is limited by comparing hand to open pollinated branches because hand pollinated flowers should theoretically be maximally pollinated. Seed number per berry was also measured in 2022 (seeds were extracted from 27 ripe berries per site). Seed set is an indicator of pollination success with more seeds per berry indicating greater pollination, fertilization, and seed development. <\/span> <\/span><\/p>\n\n\n\nData were analyzed using linear mixed-effects models using R Studio software and transformed as needed to meet model assumptions. Data are presented in original units. Our threshold for statistical significance was set at <\/span>P<\/span><\/i><0.05. <\/span>P<\/span><\/i>-values less than 0.05 were considered statistically significant.<\/span><\/p>\n\n\n\nResults and Discussion:<\/span><\/h2>\n\n\n\nIn 2021, average honey bee forager counts were the same between Beeflow treated and untreated sites (<\/span>Fig. 1). <\/span><\/b>Average return forager counts (an estimate of hive strength) were also not different between the Beeflow treated and untreated sites, with treated hives having 25.2 (\u00b13.4) return foragers\/minute relative to 31.6 (\u00b17.9) for the untreated control. Observed return forager counts were low relative to the recommendation of a minimum of 100 returning bees\/minute (Sagili and Burgett, 2011). Low return forager counts may be attributed to air temperatures frequently being below 64 \u00b0F, as the recommendation is based for temperatures of 64 \u00b0F and above. Similar return forager counts have been measured in other pollination studies in Washington blueberry pollinated by different beekeeping operations (DeVetter et al., 2016) and appears to be temperature sensitive. Fruit set was also unaffected by treatment, averaging 88 (\u00b14.5)% and 94 (\u00b10.85)% in treated and untreated sites, respectively. However, average berry weight was larger for Beeflow treated sites [averaging 1.8 (\u00b10.03) g\/berry] versus the untreated sites [1.2 \u00b10.05) g\/berry] and could be due to elevated bee visitation not captured in our forager counts. <\/span><\/p>\n\n\n\n
igure 1. Honey bee forager counts in \u2018Duke\u2019 highbush blueberry treated with Beeflow versus an untreated control (paired design; n=4 sites total). No treatment effect was detected. Data were collected from 328-ft long (100 m) transects in May 2021. <\/figcaption><\/figure><\/div>\n\n\nWhile average honey bee forager counts were the same between the treatments, there was a very observable increase in honey bee foraging on sub-optimal weather days for Beeflow treated sites indicating Beeflow stimulated foraging during suboptimal weather conditions, but the effect wasn\u2019t strong enough when looking at averages across the season (<\/span>Tables 1-2)<\/span><\/b>. Pollination conditions were overall very good for \u2018Duke\u2019 in 2021 and \u2018Duke\u2019 is a relatively easy cultivar to pollinate, which may have limited our ability to detect other potential effects from the Beeflow treatment. <\/span> <\/span><\/p>\n\n\n\nTable<\/span> 1<\/span><\/span><\/strong>. <\/span><\/strong>Honey bee<\/span> forager counts on two sub-optimal weather days in \u2018Duke\u2019 highbush blueberry treated with Beeflow versus an untreated control. Data collected in northwest Washington in May 2021.<\/span><\/span><\/p>\n\n\n\nTreatment<\/strong><\/td>2-May-21<\/strong><\/td>4-May-21<\/strong><\/td><\/tr>Honey bee countsz<\/sup><\/strong><\/td>SE<\/strong><\/td>Honey bee counts<\/strong><\/td>SE<\/strong><\/td><\/tr>Control<\/td> 41.7<\/td> 19.1<\/td> 1.7<\/td> 0.9<\/td><\/tr> Treated (Beeflow)<\/td> 106.0<\/td> 17.6<\/td> 27.7<\/td> 2.3<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\nz<\/sup>Number of honey bees\/half bush\/328-ft (100 m) transect; SE denotes standard error.<\/p>\n\n\n\nTable 2<\/span><\/span><\/strong>.<\/strong> Environmental conditions in \u2018Duke\u2019 field sites <\/span>immediately before and after<\/span> honey bee foraging was measured on 2-May and 4 May 2021 in northwest <\/span>Washington<\/span>.<\/span><\/span> <\/span><\/p>\n\n\n\nDate<\/span><\/b> <\/span><\/td> 2-May-21<\/span><\/b> <\/span><\/td> 4-May-21<\/span><\/b> <\/span><\/td><\/tr>Variable<\/span><\/b> <\/span><\/td> Before<\/span><\/b> <\/span><\/td> After<\/span><\/b> <\/span><\/td> Before <\/span><\/b> <\/span><\/td> After<\/span><\/b> <\/span><\/td><\/tr>Temp (F)<\/span> <\/span><\/td> 55<\/span> <\/span><\/td> 61<\/span> <\/span><\/td> 55<\/span> <\/span><\/td> 55<\/span> <\/span><\/td><\/tr>Humidity (%)<\/span> <\/span><\/td> 62<\/span> <\/span><\/td> 51<\/span> <\/span><\/td> 71<\/span> <\/span><\/td> 70<\/span> <\/span><\/td><\/tr>Wind (mph)<\/span> <\/span><\/td> 3<\/span> <\/span><\/td> 0<\/span> <\/span><\/td> 5<\/span> <\/span><\/td> 5<\/span> <\/span><\/td><\/tr>Pressure (inches)<\/span> <\/span><\/td> 30.24<\/span> <\/span><\/td> 30.25<\/span> <\/span><\/td> 30.24<\/span> <\/span><\/td> 30.24<\/span> <\/span><\/td><\/tr>Cloud cover (%)<\/span> <\/span><\/td> 80<\/span> <\/span><\/td> 50<\/span> <\/span><\/td> 70<\/span> <\/span><\/td> 80<\/span> <\/span><\/td><\/tr>Bloom (%)<\/span> <\/span><\/td> 60<\/span> <\/span><\/td> 80<\/span> <\/span><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n\u2018Liberty\u2019 was used in 2022 and<\/span> was selected because it<\/span> is known as a more challenging cultivar to pollinate due to <\/span>its<\/span> smaller flowers (Courcelles et al., 2013). <\/span>Despite suboptimal bloom time conditions<\/span> in 2022<\/span>, honey bee activity measure<\/span>d<\/span> as forager counts was greater in <\/span>Beeflow<\/span>–<\/span>treated sites compared to untreated sites (<\/span><\/span>P<\/span><\/span>=0.0<\/span>3; <\/span><\/span>Fig. <\/span>2<\/span><\/span><\/strong>). <\/span>Farm site also had an effect (<\/span><\/span>P<\/span><\/span>=<\/span><\/span> 0.0<\/span>2; <\/span><\/span>Fig. <\/span>3<\/span><\/span><\/strong>)\u200b<\/span>, although there was no interaction between farm site and treatment (<\/span><\/span>P<\/span><\/span>=0.56). <\/span>These data suggests that the <\/span>Beeflow<\/span> treatment can increase honey bee visitation<\/span> to<\/span> \u2018Liberty\u2019<\/span> blueberry flowers<\/span>, but there are also landscape<\/span>–<\/span>level effects that <\/span>can<\/span> influence measures of honey bee activity.<\/span> The effect of farm si<\/span>te<\/span> is unsurprising given a recent publication <\/span>t<\/span>hat shows <\/span>honey bee visitation is determined by the number of honey bee hives in the surrounding landscape<\/span> within a <\/span>0.6 mile<\/span> radius <\/span>of a field <\/span>and that field-level <\/span>stocking <\/span>densit<\/span>ies<\/span> can <\/span>miss contributions from other bees within the landscape<\/span> (<\/span>Eeraerts<\/span> et al., 2022)<\/span>. <\/span>In addition,<\/span> management could also influence honey bee visitation and is difficult to control for in field experiments. Despite the effect of field site, the <\/span>Beeflow<\/span> treatment effect was strong enough that it met our threshold of statistical significance set at <\/span><\/span>P<\/span><\/span>=0.05. <\/span><\/span> <\/span><\/p>\n\n\n\n
Figure 2. Honey bee forager counts in \u2018Liberty\u2019 highbush blueberry treated with Beeflow versus an untreated control (paired design; n=4 sites total). Beeflow increased honey bee visitation relative to the control (P=0.03). Data were collected from 328-ft long (100 m) transects in May 2022. <\/figcaption><\/figure><\/div>\n\n\n
Figure 3. Honey bee forager counts in \u2018Liberty\u2019 highbush blueberry treated with Beeflow versus an untreated control (paired design; n=4 sites total) by field site. Although Beeflow increased honey bee visitation relative to the control (P=0.03), farm site also had an effect (P=0.02) although there was no interaction between Beeflow treatment and farm site (P=0.56). Data were collected from 328-ft long (100 m) transects in May 2022. <\/figcaption><\/figure><\/div>\n\n\nAverage return forager counts (an estimate of hive strength) were <\/span>
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