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Without pollination, fruit crops won't set well. If we want to grow tree fruit we need to encourage and appreciate the pollinators we have left. As a result of my Master Gardener training I developed an appreciation for and interest in insects. As I was gardening on a fine February day I heard a bumblebee foraging in the winter blooming heather. I was suddenly curious about where bumblebees go in the winter. Not only that but it seemed to be a particularly large bumblebee. The drone of a bumblebee is a particularly soothing sound. Large and lumbering, with fuzzy bodies, bumblebees are almost cuddly, kind of the teddy bears of the insect world.
Rummaging in my files for more information about this intriguing creature, I found an article by Lloyd Eighme a retired entomologist. I had not realized that bumblebees are native. There may be as many as 40 species of bumblebee in the Western US. Not as fussy about foul weather as non-native honeybees, they go about their pollinating chores from dawn to dusk, rain or shine.
And where do they go in winter? The over-wintering queens can be seen out on sunny days as early as February. The queen sleeps under a pile of leaves, or dry grass during the coldest part of the winter. They are hungry when they wake, and search for early spring flowers. As the weather warms up they look for a nesting site, an abandoned mouse nest or thick clump of grass. They apparently don't re-use nests, which helps them avoid the predatory mites and diseases that are destroying wild and domesticated swarms of honeybees.
After establishing a nest, the queen then produces the first brood of workers, all females from eggs fertilized last fall. Smaller than the queen, the new workers gather nectar and increase the food supply. As the colony grows, the nest is enlarged and the food supply is sufficient so that by the end of summer full sized bumblebees are produced. The queen then lays some non-fertilized eggs which produce males. They mate with newly emerged females to create new queens, the only bumblebees that will over-winter to wake up and start new colonies the following spring.
Their needs are simple. Leave an undisturbed area with dry grass and leaf litter for nesting, and provide nectar sources. As I observed winter blooming heather is a favorite early spring food. Late summer blooms are also important as nectar sources. Many bees are killed by broad-spectrum pesticides; read labels and be especially careful with pesticides wherever and whenever bee are foraging.
Fruit trees also get help in the early season from the orchard mason bee. Orchard mason bees are industrious little native pollen bees that also help compensate for the loss of honeybees. They settle into holes in wood blocks, and early April isn't too late, to put up a bee block in your yard.
Females nest until June, seeking appropriate spaces to lay their eggs. Orchard mason bees are a bit fussier about habitat than bumblebees. They like to leave their eggs where conditions are warm and dry. In nature they use holes in trees which were drilled by other insects. (They may also tuck eggs under wood shingles in protected areas of houses, such as south-facing sides. This doesn't harm the house.) So place nest boxes under east or south facing eaves. They also readily accept nest blocks placed inside a small wood shed fastened to a pole. The holes need to be smooth and have an inside diameter of 5/16." Smaller holes cause the females to lay only male eggs (aren't insects amazing?). Female bees will produce the greatest ratio of female to male eggs if the holes are 6" deep rather than the more common depth of 3" or 4" in commercial bee blocks.
Unfortunately orchard mason bees also have their own mites. Beekeepers can use miticides to control the honeybee mites but no chemical control has been developed for orchard mason bee mites. The best course is to heat sterilize the wood blocks by baking in your oven at 140 degrees for 30 minutes before each new season begins, and use a straw insert system. (This helps to remove all old nesting material and clean the block out before reusing.)
Several sources sell straws of the proper diameter. Dave Pehling of Snohomish County WSU Extension devised a do-it-yourself method. He drills the wood blocks all the way through. Then cuts a sheet of office paper so it is 1" longer than the holes (red or brown paper is more attractive to the bees). Wrap this around a 1/4" dowel to make a tube, insert into your block so the outside end is flush with the front of the block, then remove the dowel. The paper roll will spring open and fill the hole. Bend the protruding end of the paper tube so it lies flat to back of the block. To keep it in place either screw a wooden back onto the block or apply two layers of duct tape to keep out potential parasites.
Starting in early March install blocks outfitted with straws. To keep them in the area to pollinate your flowers, have extra nest blocks ready to install as soon as the first blocks are filled. You can at least double the population of orchard mason bees each year by providing "housing" and a bit of mud which the female bee uses to seal up the eggs. Get out in the spring sun and help pollination proceed!
For details on these nest blocks see http://king.wsu.edu/foodandfarms/documents/MasonBee.pdf or contact your King, Pierce or Snohomish County Extension office and ask for Ag Fact Sheet 525, revised .
Hortsense: Managing plant problems with Integrated Pest Management
