Pollination Limitations and Promoting Pollination in Washington Blueberry

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1 Pollination Limitations and Promoting Pollination in Washington Blueberry Lisa Wasko DeVetter Assistant Professor, Small Fruits WSU Mount Vernon NWREC December 3, 2015

2 Blueberries in Washington Blueberries in Washington Third largest national producer 94.6 million pounds harvested from 9,100 acres in 2014 ~16% of national production Lead national organic production 4.7 million pounds harvested from 1,400 certified acres in 2011 ~50% of national production Industry is still growing Source: NASS 2012 & 2015

3 Pollination Services Insect pollinators are critical for fruit set and development in blueberry Globally, pollination services are valued at over $200 billion (Gallai et al., 2009) Single-species pollination, especially honeybees (Apis mellifera), most common in agriculture Honeybees pollinate over 130 commercial crops

4 Pollination and Fruit Set in Blueberry is a Challenge Little known if pollination is limited, what limits pollination, and how it can be optimized in Washington Improving pollination and fruit set is a program goal Reports of poor pollination and fruit set in blueberry, which limits yield Fruit set can be as low as 50-60% in western Washington, compared to 90%+ in other regions (Strik, 2004)

5 Factors that Reduce Pollination Pollination may be limited by several factors: Courcelles et al. (2013) Weather Floral morphology Pollinator-crop co-evolution Landscape features Field management Poor hive health genetics, nutrition, pests and pathogens, stress, pesticides, etc.

6 Objectives: Pollination Study Investigators: L.W. DeVetter (PI), R. Sagili (OSU), and E. Elle (SFU) Survey and evaluate honeybee activity and its role in yield within WA highbush blueberry Determine primary limitations of pollination Long Term develop guidelines and management practices so growers and beekeepers can promote pollination and yield for specific conditions encountered in WA and greater PNW

7 Approach grower cooperators 10 in western WA 6 in eastern WA 4 organic sites grower cooperators 12 in western WA 6 in eastern WA 6 organic sites Established Duke plants, % bloom

8 Approach Measured pollinator activity, as described by Courcelles et al. (2013) 10 AM to 4 PM; > 55 F N = 30 bushes/ site, measured three days Only counted legitimate visits Evaluated colony strength by counting number of incoming bees per colony within one minute

9 Data Collected Estimated berry number/bush, mean berry weight, and yield Determined seed number and quality Monitored weather Still collecting grower surveys Analyses: Comparisons across locations Test relationships between measured variables on pollinator activity and yield

10 Average number of honey bee visitations per minute in eastern and western Washington, 2014 and East Most sites below the 4-8 honey bees per bush recommendation P-value <0.001 (Isaacs et al., 2015). West Organic Organic

11 Honey bee colony strength in eastern and western Washington blueberry, 2014 and : All P-value sites below <0.006recommended 100 bees per minute (Sagili and Burgett, 2011) 2015: P-value = 0.05

12 Average temperatures during the pollination period (April- May; 10 AM 4 PM) for Lynden, Mount Vernon, and Prosser, Washington, 2014 and F *Data provided courtesy of Washington State University AgWeatherNet. Data are copyright of Washington State University.

13 Average solar radiation during the pollination period (April- May; 10 AM 4 PM) for Lynden, Mount Vernon, and Prosser, Washington, 2014 and *Data provided courtesy of Washington State University AgWeatherNet. Data are copyright of Washington State University.

14 Average precipitation during the pollination period (April- May; 10 AM 4 PM) for Lynden, Mount Vernon, and Prosser, Washington, 2014 and *Data provided courtesy of Washington State University AgWeatherNet. Data are copyright of Washington State University.

15 Results Estimated yield differed across sites, but not by region nor management Other variables showed regional and management effects Regional effects on honey bee visitation rates, hive strength, berry size, and seed number in Washington blueberry, Average no. honeybee visits/min Average no. honeybees entering a hive/min Average seed no./berry Berry size (g) Region East 5.7 a z 65 a 27 a 2.02 a a West 1.2 b 46 b 6 b 1.84 b b Significance *** ** *** * NS *** z Mean separation in columns by Duncan s multiple range test; means with the same letter are not different at P 0.05; data are presented by year if a year effect was observed. NS, *, **, *** Nonsignificant or significant at P 0.05, 0.01, or 0.001, respectively.

16 Results Regression analyses revealed few significant relationships Seed number positively related to honey bee visitation rates (R 2 = 0.25) Berry size positively related to colony strength (R 2 = 0.63) Berry size demonstrated a weak, but positive relationship with seed number (R 2 = 0.16) Scale: R 2 of 0 = Not Related; R 2 of 1 = Related

17 Promoting Pollination & Yield ~ Honeybee Management ~ Source honeybees from reputable sources Use strong hives (minimum of 45,000 bees/hive) Stocking density of hives/acre, depending on cultivar Place honeybees throughout fields at 5-25% bloom Elevate hives and provide eastern exposure Keep entrance open Remove hives at petal drop

18 Promoting Pollination & Yield ~ Cross Pollination ~ Many cultivars benefit from cross pollination through increases in fruit set (+1-58%) and berry weight (+2-33%) Cultivars benefiting from cross pollination: Aurora, Bluecrop, Duke, Draper, Brigitta, and Bluejay (Ehlenfeldt, 2001; Krebs and Hancock, 1988) Alternate rows of two cultivars with similar flowering dates (4-10 row blocks) increase cross pollination (Hancock et al., 1989)

19 Promoting Pollination & Yield ~ Encouraging Native Pollinators ~ Why natives? Co-evolved with blueberry Bumblebees (Bombus spp.) and solitary bees are more efficient pollinators Sonication promotes pollen release Active longer and during poor weather conditions Source: northwestnaturalmoments.com

20 Promoting Pollination & Yield ~ Encouraging Native Pollinators ~ Promote natives by: Conserving natural areas around perimeter of plantings Increase floral reserves through wildflower strips No- or reduce-tillage Reducing pesticide applications Hives/ bee boxes Use care if introducing natives Source: northwestnaturalmoments.com Source: Geribaldi et al., 2014

21 Promoting Pollination & Yield ~ Increasing Flower Diversity for Pollinators ~ Hedgerows or flower strips increase floral resources, increasing pollinator richness and abundance (Blaauw and Isaacs, 2014; Geribaldi et al., 2014) Demonstrated economic benefits of supplementing domestic honeybees with wild pollinators

22 Promoting Pollination & Yield ~ Pesticides ~ Pesticides are needed for crop protection Concern about impact of chronic and acute exposure of pollinators to pesticides Exercise care when selecting and deciding timing of application, especially insecticides during bloom time Follow pesticide labels Look for EPA s Bee Advisory Box

23 Reducing Pesticide Exposure How to Reduce Bee Poisoning from Pesticides (PNW 591) by Hooven et al. (2013) Beekeeper-grower cooperation Apply pesticides in the evening, when bees are less active and product has more time to dry Select least toxic insecticides with short residuals Maintain buffers between hives, water sources, and wildflowers; avoid drift Avoid tank mixes of insecticides and fungicides

24 Honeybee Attractants? Study in 2014 with foliar-applied pheromone showed greater visitation, but no increases in yield nor berry size Fruit-Boost TM = queen mandibular gland pheromone Brood pheromone shows promise (Sagili et al., 2015) Stimulates worker bee foraging, protein synthesis in nurse bees, and queen ovipositioning Example - SuperBoost Honey Bee Brood Pheromone

25 Conclusions Honey bee activity and colony strength is below recommended levels in Washington blueberry Western Washington has lower honey bee visitation rates and hive strength than eastern Washington Need for further research on ways to promote pollination in blueberry, especially in western Washington

26 Acknowledgements Project Assistance Elizabeth Elle, Tim Lawrence, Sue Coby, and Karina Sakalauskas Grower cooperators Leighton Overson, Whatcom Farmers Co-op/CNS Sean Watkinson, Rachel Weber, Carrie Scott, Ben Guadagnoli, China Moss, Matt Arrington, Rachel Rudolph, Doug Walsh, Tora Brooks, Yajun Li, and Marina Funding Washington Blueberry Commission Northwest Agricultural Research Foundation (NARF)

27 Thank you! Questions and Comments?

28 Promoting Pollination & Yield ~ Pesticides ~ Pesticides are needed in blueberry for crop protection Exercise care when selecting and deciding timing of application, especially insecticides during bloom time (Geribaldi et al., 2014) Over 121 pesticides and by-products detected in pollen, wax, and bee samples (Mullin et al., 2010) Zhu et al. (2014) found chlorothalonil increased honeybee larva mortality, especially when combined with miticides (fluvalinate and coumaphos) Other additive and synergistic effects of fungicides [Rovral (iprodione), Captan, etc.]