Alfalfa Pollination

Large commercial alfalfa field

requiring managed beehives because of its size

© Vapampidis. Wikicommons

What is the most important insect-pollinated crop? Not a fruit or a vegetable but alfalfa. Yes, alfalfa, not because we consume large amounts of their sprouts, but because cattle needs this food. Thus: no alfalfa, no beef or milk.

This crop was first introduced in California during the gold rush. Alfalfa farming grew from there at a steady pace to what it is today, the third largest crop, after corn and soy bean. A few species of bumble bees and solitary bees took a look at this exotic flower, found it to their liking and proceeded to pollinate it. It wasn't a big leap; this plant's blossoms resemble those of other members of the pea or bean family. The native pollinators were familiar with bean flowers and adapted easily to the new arrival.

Alfalfa blossom. H. © Zel. Wikicommons

Peas, beans, alfalfa, clover and several other plants have butterfly-like (papilionaceous) flowers. The lower petals form an enclosure, shaped like the keel of a boat. This structure holds the sexual parts, the anthers and pistil. When an insect lands on the flower, a trigger mechanism makes it snap open or trip the flower. This is how pollination is accomplished.

Honey bees were not present in California when the earliest fields of alfalfa were cultivated. The first beehive arrived in 1853, just one solitary hive; a few others had died in transit. It took many years for the honey bee populations to build up to significant levels. This didn't matter because the wild bees did an excellent job.

New Zealand wasn't so lucky when it started growing alfalfa to feed the recently introduced cattle. The few native pollinators were stumped by the new flower. They lacked the necessary equipment and dismissed the strange blossoms. Year after year, hay grew luxuriantly, but no seeds. Alfalfa growers resorted to importing a few species of bumble bees from Europe to cut down the expenses of having to buy seed every year. Thus, industrious bumble bees saved the day in that country.

Scotch broom, a papilionaceous flower, being tripped. © Beatriz Moisset

 Honey bees detest the rough treatment alfalfa flowers subject them to and soon learn a trick of their own. They enter the flower from the side and help themselves to nectar without tripping its mechanism. Only naïve, youthful ones pollinate flowers. Despite the honey bees' poor performance, most alfalfa farmers resort to them because of the convenience in using a managed species.

In addition to the honey bee, two other species of alfalfa pollinators are managed to some extent and used commercially. They are the Japanese alfalfa leafcutter bee and the native alkali bee.

The populations of native bees have been severely reduced in the last one hundred years largely because of intensive agriculture. Restoring their numbers and putting them to work in alfalfa fields would be an arduous task but a worthy one. Some farmers find that, when they include flowering and nesting site places in their fields or orchards, the health of the crop improves and the need for pesticides diminishes. Thus, alfalfa pollination could be done entirely and more efficiently by native bees. This form of agriculture would be more sustainable than the present methods.

List of articles
Bring Back the Native Pollinators
Will We all Die if Honey Bees Disappear?
Growing Insects: Farmers Can Help to Bring Back Pollinators
Organic Farming for Bees

Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2014

Lady Beetles. Not all are Welcome in the Garden

Asiatic Lady Beetle (Harmonia axyridis).

It poses a threat to native ones and it is a nuisance

when it gathers in large numbers

in winter in human habitations

………

 As I discussed in Native Plants and Wildlife Gardens on July 7th, not all ladybugs or lady beetles are beneficial. Some have been introduced from other lands and create trouble for the native species. Moreover, the sale of lady beetles as biological controls deserves thorough examination. You may be spending money for nothing or, worse yet, doing harm rather than good (Ladybugs,Lady Beetles or Ladybird Beetles. How Good are They?)

Mexican bean beetle (Epilachna varivestis). Stephen Ausmus. USDA

 Here are a couple of lady beetles which will surprise you. Not all lady beetles feed on other insects. A few feed on plants and may even be pests. The Mexican bean beetle (Epilachna varivestis) is just as cute as some of the most beloved lady beetles. Sadly it feeds on beans, peas and other plants of the pea family. The only consolation is that it also likes to eat that dreadful Japanese invasive plant, Kudzu.

Alfalfa Lady Beetle (Subcoccinella vigintiquatuorpunctata)

Luis Miguel Bugallo Sánchez/ Wikicommons

………

I also want to mention another pretty one, the Alfalfa Lady Beetle (Subcoccinella vigintiquatuorpunctata). It was introduced from Asia and feeds on alfalfa and an assortment of plants, such as bouncing Bet and campion. 

Another introduced species

 Seven-spotted Lady Beetle (Coccinella septempunctata)

………

List of articles
Beginners Guide to Pollinators and Other Flower Visitors

Native Bees, Honey Bees and Natural Areas

Spring beauty bee © Beatriz Moisset

It is common practice for nature centers to have a beehive. Often, a glass wall allows observation of the colony's busy life, seldom failing to catch the eye of visitors. This serves an educational purpose by providing a great opportunity for a behind-the-scenes peek at the private lives of honey bees. Thus, visitors learn about these useful insects and their role as crop pollinators.

Honey bee © Beatriz Moisset

Sometimes I wonder if we are delivering the right message. The purpose of nature centers is to protect natural wildlife and to promote conservation of natural resources. This is clearly stated in many of their mission statements. Honey bees and chickens are domestic animals. They are both important to agriculture. However, we don't keep chickens at the bird feeders to teach about birds. Do we need honey bees to teach about insects?

Nowadays, agriculture relies heavily on honey bees; however, we must bear in mind that honey bees were introduced to this continent by Europeans a few hundred years ago. Until then, all pollination was accomplished by native pollinators, more than 4,000 species of bees and many other insects, such as flies, moths, wasps and even beetles, as well as some birds and bats.

Jack-in-the-pulpit © Beatriz Moisset

Fungus gnats © Beatriz Moisset

Native plants didn't need honey bees then, and they don't need them now. A few examples should suffice. In early spring a number of delicate little flowers carpet the forest floor. They are in a rush to take advantage of the sunlight during the absence of foliage and don’t last long. Thus, they are called "spring ephemerals." None of them is visited by honey bees. In fact, many resort to highly specialized pollinators which have been around for as long as the plants themselves. Skunk cabbage and Jack-in-the-pulpit are pollinated by flies. Spring beauties and trout lilies are visited by an assortment of bees and bumble bees; but get help, in particular, from their own specialized pollinators, the so called spring beauty bee and the trout lily bee respectively.

Azalea bee © Beatriz Moisset

Shortly after, when azaleas bloom another set of specialists comes into service, the buzz pollinators. These are experts at shaking the pollen out of the flower stamens. One of these experts is the azalea Andrena bee. Its name needs no explanation.

So, what are honey bees doing in the meantime? They devote their time to the nectar and pollen of willows and maples. Thus, honey bees make use of these trees, but the trees themselves benefit from an abundance of native pollinators and don't need the extra help. Honey bees also gather pollen from hazelnuts. This is good for the bees but doesn't help the trees in the slightest because they are wind-pollinated.

Magnolia and mordellid beetles © Beatriz Moisset

Honey bees don't pollinate azaleas or rhododendrons. They also ignore dogwoods. As for magnolias and their close relatives, tulip trees, these plants are primarily pollinated by beetles and flies, all of them native. Honey bees are more inclined to visit generalist flowers, the ones receptive to a wide range of pollinators. Therefore, native pollinators are all that the flowers need.

Another problem with honey bees in natural areas is that they may contribute to the spread of non-native plants by pollinating them preferentially. They also may compete with native pollinators for floral resources.

Tricolored bumble bee © Beatriz Moisset

In summary, native plants and native pollinators are members of a complex community. They have adapted to each other and work well together. Honey bees, while important to agriculture, are not needed in natural areas. The only justification for keeping beehives at nature centers is to use them as a gate to the understanding and familiarization with insects and their usefulness. If the visitor leaves the nature center as ignorant of native pollinators as he was when he came in, then the center has failed to deliver the most valuable message of the bees.

It is imperative that naturalists and educators at nature centers with beehives devote time to informing the public about native pollinators and their significance to native plants. Posters with this information would also be helpful.

Augochlora pura © Beatriz Moisset

Tom Bain presents some good suggestions in his blog "GeoEcology. Earth and life through time..."

 "There is an essential piece missing from the typical presentation about pollination in many nature centers, that is the discussion of native pollinators and their essential continuing role in native and not so native ecosystems. Each presentation about honey bees should be accompanied by a hands-on activity to plant native plants that are partners to native pollinators, or the construction of simple solitary bee houses from dry bamboo canes or wood blocks. We would make progress if our children earned great take-home's like solitary bee bundles in place of coloring-in honey bee illustrations; and, planting native seeds to grow purple coneflower or other natives in place of marigolds, etc. A little effort and a subtle change in emphasis would shift attention to native pollinators."

List of Articles

Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2013