What We re Learning About Pollinators John Ternest February 13, 2018
Pollinators Managed Pollinators Honey bees Bumble bees Native Pollinators Bumble bees, sweat bees, carpenter bees, syrphid flies, butterflies, moths
Pollinator Importance 35% of crops are dependent on pollinators Crucial for fruit set in cucurbits Watermelon, squash, cucumbers, muskmelon, pumpkin, etc
Pollinator Diversity 3,500 species of native bees in the U.S. alone Most pollinators are not well understood Great diversity in life history, biology, size, and effectiveness as pollinators Eusocial, social, solitary Ground nesting, wood, etc As small as the width of a nickel to over an inch long
Importance of Diversity Presence of many species creates an additive effect which improves pollination Many crops rely more heavily on pollination from native species
Importance of Diversity Managed bees alone should not be relied on for pollination More vulnerable Less effective pollination
Pollinator Declines Pollinators are in decline across the globe Beekeepers are experiencing overwinter losses far greater than historically seen Colony collapse disorder Native bees at risk The rusty patched bumble bee (Bombus affinis) recently became the first endangered bumble bee species in the U.S.
Pollinator Declines Contributing factors Increasing risk from insecticide use Loss of habitat and land use change Climate change Pathogen spread
Neonicotinoids Synthetic analog of nicotine Most widely used group of insecticide in the world Highly toxic to insects, low mammalian toxicity Hyperexcitation leading to paralysis and death Imidacloprid, Clothianidin, Thiamethoxam
Insecticides Non target effects on pollinators Lethal Reduced reproductive ability Disrupted cognition, behavior, and communication Contact Direct contact Residues in pollen, nectar, water, and nesting materials Adopted from Krupke et al. 2016, Purdue Extension POL-4
Insecticides Neonicotinoid sales (a) and usage (b,c) between 1992 and 2011 Adopted from Douglas and Tooker 2015
Insecticides Thiamethoxam and Clothianidin use in the U.S. from 2004-2014
Insecticides Risks in Indiana Yellow represents areas with neonicotinoid treated corn Left: Neonicotinoid risk without considering drift from treated fields Right: Neonicotinoid risk expanded to account for 90 m of drift Adopted from Krupke et al. 2017
Cucurbit Production Cucurbit crops have an annual value of $1.5 Billion in the U.S. Includes cucumbers, watermelon, pumpkin, muskmelon Susceptible to pests and bacterial wilt (Erwinia tracheiphila) which is vectored by the striped cucumber beetle (Acalymma vittatum). Intense management Thresholds as low as 1 beetle/plant
Watermelon Indiana is among the top watermelon producing states in the U.S. Transplanted as seedlings Transplant mid-may, final harvest August Watermelon fruit set is entirely dependent on pollination Male and Female flowers, Seedless varieties Watermelon not susceptible to bacterial wilt
Striped Cucumber Beetles The striped cucumber beetle is the primary pest of concern in watermelon. Overwinters as an adult Two generations present during the season Damages leaves, stems, roots, flowers, and fruits Watermelon threshold: 5 beetles/plant
Management Insecticides Neonicotinoids Pyrethroids Application Method Seed Treatment Soil Drench Foliar Sprays Application Time IPM Pest Thresholds Temporal Tank mix Alternative Management Natural Enemies Rotations Trap Crop
Trade offs Growers in agricultural systems face trade-offs as a result of management practices. Insecticide use Pests vs Beneficial Insects How to successfully manage these trade-offs?
Hypothesis and Prediction Hypothesis: Reduced insecticide inputs will improve pollinator health without compromising pest management. Prediction: Currents practices apply insecticides when insect pests are below ET s, resulting in non-target pollinator exposure. These applications below ET s are unlikely to provide any yield benefits due to pest suppression.
Objectives Assess Pollinator species present in watermelon fields and their impact, to better understand how to limit non-target exposure. Quantify field realistic insecticide exposure in watermelon fields using various management strategies. Identify management strategies which provide optimal pest management while prioritizing pollinator health.
Methods Watermelon Fields Farm Field Size (acres) Description of Operation 1 1.78 Conventional, Diversified 2 3.29 Conventional, Diversified 3 2.00 Conventional, Diversified 4 0.686 Organic, Diversified 5 0.578 Conventional, Diversified 6 20.5 Conventional, Diversified 7 100.0 Conventional, Monoculture 8 22.4 Conventional, Diversified 9 43.0 Conventional, Monoculture 10 31.7 Conventional, Monoculture 11 2.50 Conventional, Diversified 12 15.7 Conventional, Monoculture 13 28.0 Conventional, Monoculture 14 13.7 Conventional, Diversified 15 29.5 Conventional, Monoculture
Sampling Pest Sampling Striped cucumber beetles sampled on individual plants Assess pest pressure Pollinator Sampling Pollinator visual sample and collection Catalog pollination services and pollinator species present in fields Residue Sampling Pollen, leaf, and soil samples Quantify insecticide residues in fields which could lead to pollinator contact
Pest Sampling Scouting for IPM Pest Sampling Regimen In order to confidently determine striped cucumber beetle presence in watermelon only 15 plants need to be sampled Easy and effective way to practice Integrated Pest Management strategies and utilize thresholds Mean Density 0.5 1 2 3 4 5 10 Number of Samples (n) 85 50 30 22 18 15 9
Results
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Pest Sampling Data No field observed to have reached threshold for a sampling date (142 total sampling dates) 29 out of 2828 total plants sampled (1%) had five or more striped cucumber beetles 7 out of 15 fields never had a single plant with five or more striped cucumber beetles
Field abundance ranges from 19-80 collected pollinators Average abundance 40.8
Diversity may be a better indicator of pollinator health Great reliance on managed honeybees vs. wild pollinators Management seems to play a larger role in pollinator health than pest abundance.
Conclusions Despite varying management strategies, we never observed threshold for striped cucumber beetles on any field. Effective pest control in all fields! Pollinators are a key factor in fruit set and yield so protecting pollinators should be effectively balanced with pest management. Insecticide residues being analyzed, treatments below ET s are expected to increase pollinator contact without improving yield as a result of pest management.
Future Directions Watermelons grown in high tunnels Managed B. impatiens colonies placed in high tunnels Quantify insecticide residues Quantify impacts on B. impatiens colony health, brood production, foraging efficiency
Research Goals Quantify insecticide residues Quantify impacts on B. impatiens colony health, brood production, foraging efficiency Preliminary study testing field realistic impacts on colonies in various environments
Questions?
Honeybees Primary Managed Pollinators Large eusocial colonies, queen and workers Generalist foragers Introduced to North America Mid-size bees
Bumblebees Native to North America New managed pollinator (Bombus impatiens) Primitively eusocial colonies, queen and a 100+ workers Generalist foragers Large bees
Sweat Bees Native to North America Solitary species, males and females Generalist foragers Small bees Diverse appearances, bright green, blue, black, tan with various patterning
Syrphid Flies/Hoverflies Native to North America Not bees Small to mid-size Diverse appearances, often look like bees