Lecture 7 Pollinators.pdf

Pollination Biology Ent 104 Johnson Outline Overview of a rapidly evolving field A little about crops and flowers Agricultural landscapes and pollination Honey bees as managed pollinators Other bees as managed pollinators The Big Picture: Bees and Crops About 100 U.S. crops are at least partially de...

Pollination Biology Ent 104 Johnson Outline Overview of a rapidly evolving field A little about crops and flowers Agricultural landscapes and pollination Honey bees as managed pollinators Other bees as managed pollinators The Big Picture: Bees and Crops About 100 U.S. crops are at least partially dependent on bees – ≈ 400 worldwide About 1/3 of our food directly or indirectly comes from “honey bee pollinated” crops – Indirect Animal feeds – Maximum amount Billions of dollars per year – Honey bees are a key component of industrial agriculture Common crops pollinated by bees Fruits Vegetables Nuts Apples Strawberries Tangerines Cantaloupe Watermelon Pumpkin Kiwis Avocado Apricot Cherries Plum Peach Pear Raspberry Blueberry Cucumbers onions Carrots Celery Cabbage Brussels Sprouts Broccoli Cucumber soybean Almonds Brazil nut Hazelnut Macadamia Chestnut Cashew Animal Feed / Spices, other Clover Alfalfa Cotton Cardamom Coriander Mustard Pollination Basics Many angiosperms need animal vectors to reproduce – Not grasses, gymnosperms, ferns, moss, etc Flower Morphology Plant reproductive biology is complicated Flowers – – Perfect Male & female Imperfect Male or female Plants – Monoecious / Dieocious Plant has male and female flowers, or perfect flowers Whole plant has male or female flowers only Cultivars – – Self-fertile Self-infertile Agricultural Applications Biological characteristics 1. Flower type 2. Flower presentation on plants 3. Ability or inability to self All lead to: A pattern of planting for optimal pollination May not be the most productive biologically From University of Missouri extension Complications! Flower Morphology – Some flowers are easier to pollinate than others Bees rob – Avoid getting pollen on themselves More Complications Not all flowers are equally attractive to bees – Nectar Concentrations vary widely Pollen production also varies – Leads to – – large fields clean farming Kill dandelions Crop Sugar Concentration Pear 2-37% Apricot 5-25% Plum 10-40% Almond 16-36% Peach 20-38% Apple 20-58% Raspberry 21-60% Cabbage 30-59% Cucumber 35-45% Onion 40-75% Canola 45-60% Dandelion 38-46% Benefits of cross pollination even for species that are self compatible Highbush blueberries are self fertile, yet cross pollination: – Increased fruit size 14% – Increased market value 43% Lang and Danka 1991 Agricultural Ecosystems Low plant diversity – Series of monocultures Heavily manipulated soils Heavy pesticide use Low Plant diversity No year round forage – Boom bust flower cycle No variety in pollen sources – Different pollens have different nutrient profiles – Leads to poor diet in some cases – Leads to artificial feeds Not optimal No suitable nesting sites for many native pollinators – No twigs, leaf litter, etc Heavily manipulated soils Reduced nesting sites for native pollinators – Bumble bees Mouse nests Heavy brush – Solitary bees Sandy soils Twigs Heavy Pesticide Use Kills beneficial (pollinators) as well as destructive insects – Kills predators of pests, too Monoculture can increase pollination demands beyond natural capacities Natural communities are diverse – Relatively low demand for pollinators – Pollinator populations are relatively small Monoculture creates enormous unnatural demands for pollinators Crop can be a poor attractant of bees Even a healthy pop of pollinators next door might not be enough! Agricultural ecosystems in summary Highly unnatural Destructive to native pollinators – Pesticides – No nest sites – No consistent forage Massive temporary demand for pollination What we’d like… What we often have Why the honey bee? Bumble bees Solitary bees Honey bees Bumble bees Orchard bees Alfafa leaf cutter bee Apis Honey bee 1. The honey bee is a generalist – Not necessarily the best for any given crop 2. Honey bee societies are large 3. The honey bee can be manipulated 4. The honey bee can be managed Why bumble bees in Agriculture? Some flowers require buzz pollination Tomatoes, eggplants, etc Bumble bees (and many other bees) do it Honey bees do not Before commercial rearing of bumble bees tomatoes in greenhouses were mechanically pollinated At great expense Bees in the greenhouse Solitary bees as managed pollinators All bees are pollinators Any bee could in theory be a managed pollinator Problems to overcome: – Rearing them in large numbers – Getting them to stay near the crop – Keeping them healthy Ground nesters: Alkali bee Blue Mason Bee Megachilid bee used for tree fruit pollination Separates nest cells with mud Moves from row to row in orchards – Honey bees move down rows Not used on a large scale yet – Was much interest in doing so from academics http://www.ars.usda.gov/Research/docs.htm?do cid=18333 Alfalfa pollination The flower has to be tripped for pollination to occur Honey bees learn to avoid the tripping mechanism and so do not always pollinate the flowers – Temperature and humidity dependent – Density dependent Many honey bees will still trip the flowers Cane 2002 Overview of how to use Leaf Cutter Bees They come as free cells (usually) – Can also be bought pre-hatched Set up enclosure near crop – Or in the middle of the crop Put bees into enclosure – As live bees or closed cells They hatch and begin their lives – Many choose to live in the predrilled holes if food is available near by Commercial use