Understanding Pest and Disease Transmission Dynamics and Effects of Agrochemicals on Honey Bee Colonies Pollinating Crops in the Western States

Understanding Pest and Disease Transmission Dynamics and Effects of Agrochemicals on Honey Bee Colonies Pollinating Crops in the Western States

Summary

Honey bee pollination is estimated to be worth more than $17 billion in the U.S. (Calderone 2012). Honey bees are critical for production of several crops in the western states, including California almonds which account for 75% of world production and are valued at $3.6 billion. When other cropping systems are included, West Coast beekeepers provide nearly half of the nation’s commercial pollination services. Recent annual honey bee colony losses (averaging 30%) are alarming to both beekeepers and growers, who are interdependent for their economic viability. Beekeepers have identified several areas of concern in the West Coast pollination circuit. Risks to honey bees include (1) pathogen exposure and transmission between closely packed colonies in holding yards, (2) exposure to agrochemicals (e.g. fungicides and insecticides) applied during bloom, and (3) poor nutrition.

The pollination year begins when the majority of commercially managed honey bee colonies (~1.5 million) are transported to California to meet almond pollination demands each February. The almond cropping system represents an incubator for epidemics as colonies across the nation are transported here for pollination. This could severely affect the entire country’s pollination services. In spite of this potential threat, there is little prospective pathogen monitoring of honey bee and none reaching the scope of our proposed work.

During almond bloom, and in each subsequent pollinated crop, honey bees are exposed to multiple applications of agrochemicals. Many of these pesticides persist in hive materials, resulting in prolonged exposures. These exposures may weaken colonies and make them more likely to succumb to the diseases and pathogens they contracted from closely placed colonies in almonds. Our goal is to characterize synergistic effects between agrochemicals and honey bee diseases, which has been little investigated in field settings. Our results will help to mitigate risk to pollination services for almonds and other crops (blueberry, seed crops, melons) dependent on bee pollination.

Together with beekeepers and growers, we have identified pesticide groups and exposure scenarios of particular concern during the pollination year. These include fungicides sprayed during almond and blueberry pollination, novel antifeedant insecticides applied during pollination of seedcrops, and neonicotinoids used in chemigation systems in watermelons. Our strategy is to monitor transfer of pests and pathogens and exposure to fungicides and insecticides in selected experimental colonies during pollination of these crops. By correlating our results with stakeholder input and survey responses, we will identify practices that minimize bee diseases and pesticide exposures that effect honey bee colony health in these crops. Multiple communication tools will be used to solicit input and encourage cooperation between multiple stakeholder groups in implementing strategies suggested by our results. The stakeholders (beekeepers and growers) will be involved during all phases of this study, including designing experiment to data collection. The information obtained from this study could potentially be used in other bee pollinated crops to promote bee health and pollination services.

Objectives/Performance Targets

Objective 1: Analyze patterns in management practices that potentially affect honey bee colony health in almonds, carrot seed, and watermelons.

Both grower and beekeeper practices that are likely to influence pesticide exposure and disease transmission in bees will be investigated. By evaluating colony health and the concentration of fungicides and insecticides in hive materials, the success of these practices will be assessed.

i) Evaluate management practices that affect honey bee health
ii) Correlate concentrations of pesticides in bee bread and comb wax with application timing and methods
iii) Survey beekeeper and grower behavior, attitudes, and economic data

Objective 2: Isolate risk factors using laboratory and semi-field studies

We will perform controlled experiments to identify practices that are most and least likely to result in colony losses.

i) Identify parameters that decrease transfer of pests and pathogens between selected experimental colonies
ii) Characterize toxicity of selected pesticides and assess their risk to bees at field concentrations

Objective 3: Identify strategies to improve colony health and mutual economic benefit

We will identify the factors which incur the most risk to colonies and work with stakeholders, particularly our advisory panel, to analyze the cost and feasibility of modifying these practices.

i) Identify significant risk factors
ii) Work with stakeholders to weigh cost/benefit/feasibility of potential interventions to growers and beekeepers

Objective 4: Synthesize and disseminate new information and measure impacts

Using multiple methods, we will communicate best practices to stakeholders.

i) Conduct stakeholder advisory panel meetings to review scientific results and direct communication of best practices
ii) Create outreach and informational materials
iii) Design evaluation tools to assess economic, social, and environmental impacts

Accomplishments/Milestones

As a part of objective 1 we sampled experimental honey bee colonies during 2016 in four cropping systems (almonds, blueberries, pears and carrot seed). We sampled 144 colonies pertaining to the collaborating beekeepers during almond pollination between February 5 and February 7, 2016 at six different sites in California. The same 144 colonies were sampled for second time between February 23 and 25. Samples were obtained from these colonies again when they were placed in blueberry (between April 12 and 22), pear and carrot seed crops. The final sample for 2016 was obtained when the experimental colonies were in respective winter yards in October. Bee samples were analyzed for pests/pathogens (Varroa, Nosema) and pollen samples were stored in freezer for future pesticide analysis. Further, colony evaluations (number of frames of bees) were performed for all the experimental colonies.

We also sent an extensive survey to both beekeepers and growers to gather information pertaining to management practices.

Impacts and Contributions/Outcomes

WSARE Agrochemical Study 2016 Figures of Results

Collaborators: