What We’re Learning About Pollinators

John TernestFebruary 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 materialsAdopted 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

• Thiamethoxamand Clothianidinuse in the U.S. from 2004 -2014

Insecticides – Risks in Indiana

Adopted from Krupke et al. 2017

• 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

• 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

Cucurbit Production

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.

Farm Field Size (acres) Description of Operation1 1.78 Conventional, Diversified 2 3.29 Conventional, Diversified3 2.00 Conventional, Diversified4 0.686 Organic, Diversified5 0.578 Conventional, Diversified6 20.5 Conventional, Diversified7 100.0 Conventional, Monoculture8 22.4 Conventional, Diversified9 43.0 Conventional, Monoculture

10 31.7 Conventional, Monoculture11 2.50 Conventional, Diversified12 15.7 Conventional, Monoculture13 28.0 Conventional, Monoculture14 13.7 Conventional, Diversified15 29.5 Conventional, Monoculture

Watermelon Fields

Methods

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

Mean Density 0.5 1 2 3 4 5 10

Number of Samples (n) 85 50 30 22 18 15 9

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

Results

5

• 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

Pest Sampling Data

• 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.

• 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.

Conclusions

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

• 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

Research Goals

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