The Art of Pollination in Cages with Insects

“Everything there is to know about the bees and flies used in controlled

pollination cages at NCRPIS, Ames, IA”

S.J. Hanlin and S.G. McClurg

Entomology Project November, 2005

Why do we use insect pollinators ?

The NCRPIS maintains collections of diverse germplasm. Controlled pollination of individual accessions helps retain the original genetic diversity of the plant populations. Some plants are more effectively pollinated by insects than by hand. In addition, insects may be more economical than hand pollination of some crops. At NCRPIS, insect pollinators are added to caged accessions of Brassica, miscellaneous umbels, sunflowers, and vegetables, as well as some ornamental and medicinal species.

Primary insect pollinators used at NCRPIS

• Honey bees or Apis mellifera

• Osmia lignaria or blue orchard bee and O. cornifrons or hornfaced bee

• Bumblebees or Bombus impatiens

• Houseflies or Musca domestica

• Blue bottle flies or Calliphora sp.

• Alfalfa leafcutter bee or Megachile rotundata

Honey bees• Social bee with 2 - 4000

bees/cage• Brought to U.S. by European

colonists• Traditionally used to pollinate

many different plants• Forage best from 15 to 32 C

(60 to 90 F); don’t fly when wind speeds exceed 25 MPH

• Rearing well established but costly due to equipment and regular care required – $82.50 for single story nuc– $86.75 for double story nuc

• Aggressive, sting

Honey bee management at NCRPIS• Source of bees: Maintain own colonies supplemented with purchased queens or

packages in the spring as needed• Work is done by controlled pollination supervisor and 2 to 3 crew members• 6 outlying bee yards in the Ames, IA area

– 150 Parent colonies (3 story hives with 10 frames per story) – 800 Nucleus hives (1-2 stories with 6 frames per story)

• Spring time– Check health of overwintered bees– Begin making specialized nucleus hives and queen cells in April– Begin “nuc” placement into field cages

• Summer time– Continue making nucs and queen cells until mid August– Place nucs into field cages at curators request (ca 90 weekly)– Feed weekly with corn syrup solution and pollen patty bi-monthly

• Fall/Winter– Monitor bees for mites; treat as needed– Combine or discard queenless or very weak nucs– Move strongest nucs and 2-story parent colonies to overwintering building– Winterize 3-story parent colonies left outside– Clean and repaint vacant equipment

Honey bee use at NCRPIS

• Major insect pollinator utilized

• Placed in ca 800 cages per year

• Can be used year round

• Used in both field and greenhouse cages

• Used to replace Osmia in Brassica cages

• Used in conjunction with flies in umbels

What is a “nuc” ?A “nuc” or nucleus hive is a smaller version of a normal honey bee hive.

• Structure of nuc– One or two stories with bees on frames of

wax comb– Bottom board with specially designed slide

that allows bees to fly either direction from the box (inside or outside of cage) or to be confined within the box

– Lid with feeding hole

• Contents of single story = 6 frames total– 2 frames with honey/pollen– 3 frames with worker bees and brood (bee

larvae)– Queen bee– 1 frame of empty comb– Weighs ca 20 pounds– Contains ca 2000 bees

• 2 story nuc– Weighs ca 50 pounds– Contains 4000 bees– Frames contain: Lower box has brood and

upper box has honey/empty comb

Honeybee positioning into two cage sizes

Nucs are generally placed in the northwest corner or north end of the cage.

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1999 2001 2003 2005

Honey bees used at NCRPIS from 1999 - 2005

Honeybee/year

Overall bees/year

Osmia• Solitary bee; ca 40 bees per

cage • O. cornifrons brought from

Japan in 1977, O. lignaria native to U.S.

• Excellent for early season plants (Brassica and fruit trees)

• Will work 10 to 32 C (50 to 90 F) during the spring

• Rearing is established; cannot be manipulated further

• Cost $17.50/small domicile• Cannot relocate domiciles from

original placement during pollination season

• Non-aggressive

Osmia management at NCRPIS• Source of bees:

– NCRPIS increase from 6 outlying locations and from small field cages– Ca 1500 to 2500 bees are purchased annually from supplier in the U.S.

• Domicile is PVC pipe (5 or 7.6 cm diameter) suspended via eye-bolts from 1.25 m metal rod bent at 45 degree angle ca 1 m from bottom

– PVC end cap placed on back; front of pipe is cut at an angle to reduce weather damage to straws inside

– Small domiciles for germplasm cages contain 4 filled straws (ca 32 bee pupae) in bundle of 16 cardboard tubes

– Large domiciles for bee increase contain 5 filled straws (ca 40 bee pupae) in total of 23 cardboard tubes; front of domicile covered with mesh screen to protect from predators

– Bees need a source of mud for forming walls between cells in nesting straws• Osmia domiciles are collected in early July and stored at 26 C (80 F)

– Domiciles must be handled carefully to prevent dislodging developing larvae from pollen balls within the nesting straws

– Nest straws will be invaded by a variety of Hymenoptera• Mid-November straws are removed from domiciles and examined for bee

pupae before winter storage at 4 C (40 F)• In March straws are placed into new domiciles ready for springtime use

Osmia use at NCRPIS

• Used in ca 200 field cages of Brassica annually from April – June

•Can be used in cool greenhouse cages beginning in April

•Used for some miscellaneous umbels and ornamentals

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Osmia used at NCRPIS from 1999-2005

Osmia/year

Overall bees/year

Bumblebees

• Social bee with ca 50 bees/colony

• Use U.S. native species• Excellent pollinator of

many plants• Work in rainy, cool (13 C

or 55 F), windy weather• Active for long hours• Rearing is difficult so

commercial colonies are used

• Expensive ($100 per unit)• Mildly aggressive

Bumblebee use at NCRPIS

• Bumblebees are used in ca 10 cages per year• Used mainly for ornamentals with trumpet shaped

flowers as bumblebees have long tongues• Used in both field and greenhouse cages• Can be purchased year round but availability may be

limited by demand• Queenright colonies may be too aggressive in working

cages with tender or few flowers; Drone colonies are more “mellow”

• Occasionally we collect “wild” bumblebees for temporary cage use; put 3-5 bees per cage which live ca 5 days

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Bumblebees used at NCRPIS 1999-2005

Bombus/year 0 0 9 15 12 4 12

Overall bees/year 396 867 824 707 674 1031 877

1999 2000 2001 2002 2003 2004 2005

Houseflies and Blue Bottle flies

• Place ca 200 flies per cage each week

• “Incidental” pollinators• Work at average temperatures • Rearing is well established;

pupae are low cost, cost varies per number of pupae purchased

• Require pre-conditioning of pupae prior to cage release for good emergence; no care required for adults

• Non-aggressive but may be considered “irritating”

Fly management at NCRPIS• Fly pupae are purchased

– BBF from Idaho every 2-3 weeks; stored at 0 C (32 F) for up to 3 weeks

– HF from ISU Ent project picked up weekly; cannot be stored

• Fly pupae are incubated on a weekly schedule

– 2-3 days at 26.5 C (80 F) – Half-pint paper cartons with

screened lids– Better adult emergence

• Fly pupae HOLDERS– One quart plastic containers

weighted with plaster and exit hole cut out at top

– Gives flies a place to hide during inclement weather

– Protects pupae from people entering cages

Use of flies at NCRPIS

• Flies are used primarily for pollination of Daucus and other umbels

• May use as “fill in” pollinator for other crops (e.g. Erysimum, Crambe) when bees unavailable

• Used in ca 40 greenhouse cages in the winter and ca 20 GH cages in the spring/summer

• Used in ca 80 field cages in the summer• Flies are replenished in cages weekly due to their short

life span; live 2 to 3 weeks• Using two species of flies together or flies along with HB

has been shown to increase seed quantity and quality

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Flies used at NCRPIS 2003-2005

Winter-Spring GH

Summer Field

Summer GH

Fall GH

Alfalfa leafcutter bee• Why use ALC ?

– Pollinator to supplement honey bees– Wanted insect easy to rear with

established management – Non-stinging preferred– Largest unmet pollination demands:

• Wild cucumis in GH cages• Late-blooming wild-type

sunflowers– Bee Biology/Systematics Lab, Logan,

UT recommended ALC

• TRAITS of ALC:– Solitary bee; use 20 to 40 bees per

cage, replaced ca every other week– Introduced to U.S. from Europe ca 1930– Traditionally used for pollination of

forage legumes and blueberries– Work at 26 C (80 F) or above but not

frequently in cool cloudy or rainy weather, prefer dry sunny climate

– Rearing is established; bees are low cost ($100/gallon) and require little care

– Non-aggressive but will bite if squeezed

Use of ALC bees at NCRPIS is still in the research stage !

• Lab work done 2004-2005 showed ALC can be used as greenhouse pollinator in winter/spring – Early emergence of bees from cells is possible, but

bees will not live for an extended time until a springtime “trigger” occurs

– Continuous incubation allows for weekly replacement of bees

– Extended emergence test (into fall) is underway now• We are collecting “bare bees” rather than

releasing them with cells as growers do– Parasitoids (tiny wasps, ca 3 species) are a

problem/concern– We can release a known number of bees per cage

ALC management: Cool (4 C or 40 F) storage and pre-incubation at room temperature

• Cells obtained from Canadian or western U.S. suppliers stored in screen trays or vented jars

• Cell depth should not exceed 3.8 cm (1.5 inches) for reduced mortality

• Pre-incubation at 23-24 C (73-75 F) for several days prior to warm incubation

ALC management: warm incubation and bee collection• Cells incubated for 30 days at 30 C (86 F) for complete bee emergence

• First two weeks incubated in dark, then placed in chamber with limited light period

• Bees collected daily; provided wood nest cell and sucrose soaked wicks

• Retrieved ca 43 sets of bees (20 bees/set) from ca 2400 cells

• Parasitoids are controlled with 24 hour black-light/water trap

Domiciles seem important in extending life span and activity level of ALC bees

• Female bees carry pollen; providing domicile encourages them to work flowers in order to nest

• Cut disks from leaves and petals for nest cells

• Manmade domiciles have evolved from wood to styrofoam blocks; some models we tried in 2005 field and GH

2004 – 2005 Field Tests• 2004: Compared HB to ALC in cages

– 8 accessions– No significant difference in quantity or quality

of seed produced

• 2005: Compared HB to ALC with and without alfalfa nesting plant– 6 accessions– Seed processing is in progress

Accessions ALC appeared highly attracted to in 2005 field/GH cages

ALC seem to be most effective at pollinating small to medium sized flowers of a “flat” nature

• Angelica• Brassica napus• Cucumis • Daucus• Helianthus (wild-type heads)• Melilotus• Ocimum• Potentilla

Cucumis photo courtesy of L. Clark, NCRPIS

Daucus umbel pollinated by ALC

International Pollination Symposium 2006

July 23 – 27, Iowa State University, Ames, IA

"Host-Pollinator Biology Relationships - Diversity in Action"

http://www.ucs.iastate.edu/mnet/plantbee/home.html

Questions ?