February 20, 2012
“For bees, the flower is the fountain of life and for flowers bees are the messengers of love” - Dennis VanEngelsdorp
Spring is upon us and our gardens are coming alive; plants have broken dormancy and the buzz and hum of the precious and fascinating pollinators have joined in the musical chorus of the garden. Most pollinators have had a hard time of it lately, however, both the introduced honey bees and the plethora of native pollinators.
Plants and their related pollinators have co-evolved over 15 million years to produce the delicate and sometimes amazingly detailed balance of give and take; honey and pollen in exchange for sexual services rendered; the transfer of pollen from stamen to stigma. Pollinators are the awe-inspiring intersection between the plant world and the animal world.
About 25% of plants are able to exchange pollen by wind. The rest rely on pollinators to do the job. Fruit and seeds are the result; the procreation of the plant world. While only 15% of our crops are pollinated by exotic honeybees, that still accounts for about 15 billion dollars worth of crops each year in the U.S. and represents one out of every three mouthfuls of food most people eat. These imported pollinators are important to our economy and our food supply.
Most have heard about the decline in honeybee health and Colony Collapse Disorder or CCD. This has devastated the bee industry, as about 30% of commercial hives have been lost in each of the last three years and yet some crops such as the almond crop of California are dependent on them, requiring a staggering 1.5 million colonies of bees. CCD has been refined to mean the loss of hives to various causes but primarily viruses and especially IAPV or the Israeli Acute Paralysis Virus. Other viruses also include RNA viruses that can be transmitted through pollen pellets and honey, some having been proven just as deadly to some of our native bumble bees and wasps.
Bumble bees also have problems with intercellular parasites. A three-year study completed in 2011 showed a 96% decline in four of the species studied. A fungal disease called Chalkbrood is wreaking havoc on the alfalfa leafcutting bees and a fungus called Nosema is also a culprit, often found alongside IIV6, a DNA virus.
Other components of CCD include Varroa mites, which feed on bee blood and transmit viruses, including IAPV and IIV6. Habitat loss, pesticides, inadequate diet, and global warming have all contributed to stress and the resulting immune suppression. The growing use of the pesticide Imidacloprid, found in a growing number of pesticide products, has also been implicated in the problem. The bottom line is that both the diverse native bees and the imported honey bees desperately need our help by providing healthy environments that offer clean water, an absence of pesticides, a safe habitat, and a diverse pallet of nectar producing plants throughout the season.
Native bees are highly diverse, including thousands of species of bumble bees, sweat bees, carpenter bees, and many others. Native bees are often solitary, stingless, and sometimes quite small. They are generally more efficient individually at pollinating than honey bees and this helps make up for their lack in numbers. Many need holes or bare earth to rear their young. For this reason, an area free of tilling and heavy mulch is desired in the garden. Bee “houses” can also be made or purchased that supply a variety of diameter holes to help promote their survival.
Bees are not the only pollinators by far. Bats are also important pollinators and likewise are dying out in huge numbers. Nocturnal or dusk feeders are attracted to cacti such as barrel cacti or prickly pears. Supporting the conservation of native cacti and bat habitat is an important part of the solution.
Hummingbirds are also important pollinators. They feed about every 10 minutes all day and consume up to 2/3 of their body weight by extracting nectar at the rate of about 13 licks per second and can service 20 flowers per minute. This amount of sugar is necessary to keep their wings beating at up to 55 beats per second and allowing them to fly at speeds up to 50 mph, to hover, or even fly backwards or upside down. They are primarily attracted to tubular flowers. Attracting them to your garden is easy and can be especially rewarding.
Butterflies and moths also need our help. Giving them a spot with some mud for them to drink from can help lure them to the garden. Moths go after nocturnal trumpet-shaped fragrant flowers, usually white or cream colored. Plants for the caterpillars to feed on and eggs to be hatched on such as milkweed are also necessary for their survival. Remember that the bacterial pesticide BT is poisonous to all Lepidoptera larvae (caterpillars), not just the pests.
The rule with plants as it is with any ecosystem is diversity. Tubular flowers (such as California fuchsia, penstemon, honeysuckle, lobelias and the sages) plus flowers that have many small florets including composites (such as sunflowers, coneflowers and daisy-like plants), umbels (such as dill or fennel) and other inflorescences that likewise have many small flowers close together such as yarrow. Other plants such as currants, ceanothus, manzanita, gum plants, buckwheat, and even trees such as the buckeyes are fantastic plants for pollinators. Basically, many small florets that can be harvested with out much effort and a diversity that offers overlapping blooming periods is best. Some non-natives such as clovers, mints, lavenders or thymes can be beautiful as well as helpful to the pollinators.
Another added benefit of these types of flowers is that they attract many other beneficial insects that can prey or parasitize pests in our gardens and create a more balanced ecosystem. Two of the best garden elements to try and create to promote pollinators are the meadow area and areas or “islands” for habitat. The traditional mowed and “weed-free” lawn is the worst. 11% of pesticides used and 5% of greenhouse gases are produced maintaining lawns. By transitioning old lawn areas into non-mowed, diverse meadows or climate-appropriate plants with nectar producing plants on drip, the pollinators will have a much better chance to survive in their increasingly stressful environments. Without them, our survival is in grave danger as well.
Gretchen LeBuhn will speak about ”Protecting Pollinators” in a lecture sponsored by the UC Marin Master Gardeners.
Gretchen is an enthusiastic supporter of “The Great Sunflower Project,” a backyard bee count.
The talk will be held at Marin Art and Garden Center, 30 Sir Francis Drake Blvd., Ross, at 7 p.m. on Thursday, March 1.