How important are pollinators?
Over $1.2 billion of Canadian horticultural produce depends upon insects for pollination. Without insect helpers, we would not enjoy apples, pears, cucumbers or melons. Strawberries would be extremely expensive.
There are over a thousand species of pollinating insects in Canada, but of these only five are used domestically (honeybees, mason bees, certain bumblebees and two kinds of flies for greenhouse pollination). The others are essential to gardeners and farmers too, but little is known about their populations and their habits.
Sadly, domesticated honeybees are suffering severely from an epidemic of parasitic mites that threaten not only the honey industry, but also the fruit and vegetable produce that depends on this very important pollinator. Pollination has always been taken for granted, but it is a resource that may need to be managed in the future. We need to understand these important insects better!
Wild pollinators are “keystone species”, meaning that most other species in their ecosystems depend on them, either directly or indirectly. Plants depend on pollinators to help them make seeds for their reproduction, and birds and other animals depend on those seeds for food too. Without wild insects pollinating flowers, the whole food chain suffers.
What’s your history, honey?
Our ancestors started collecting wild honey at least four to five thousand years ago and beekeeping may have started as early as 3,500 years ago. Domesticated honeybees arrived in North America with the earliest European settlers around 1638. The eastern honeybee (Apis cerana) is indigenous to India, China and Japan and is domesticated in some parts of the world. The European honeybee is the one found in North America, Apis mellifera.
What does it take to make honey?
A pound of white clover honey is the result of nine million flowers visited by honeybees.
Although not native to North America, the common honeybee is the most important insect pollinator. They collect both nectar and pollen to supply their complex social system. They are easily handled by beekeepers and are much more valuable as pollinators than as honey producers. They have long tongues, hairy pollen-collecting coats, the ability to warm themselves, and a high frequency of floral visits during their lives. Honeybees live year-round, so they must use whatever plants are in flower (polylectic) and cannot afford to specialize.
A honeybee colony has one queen, several hundred drones (males) and around 30,000 workers, depending on the season. The queen can lay 2,000 eggs a day.
Honeybee declines that result from parasitic mites include the tracheal mite originally from South America, and the varroa mite, originally from Asia.
How about that -- insects and flowers have evolved together.
The co-evolution of insects and flowers is reflected in the diversity among pollinators. To pollinate a flower, pollinators must visit and forage in such a way, within a specific period, that viable pollen is transferred to other flowers. Individual flowers must reward, but not satiate, visitors so that they carry pollen to other flowers of the same species. The correct insect anatomical and behavioural fit and floral advertisement and rewards are required. Many flowers are effectively pollinated by a diversity of animals. Very few plants are pollinated by a single species. An insect must be a frequent floral visitor in order to be effective. Because a plant only requires its pollinators for short periods of the year, these insects must either forage at other plants or shorten their adult life and schedule it to that particular flowering period.
The plant-insect relationship is now in peril because of the many threats facing pollinators with the most specialized relationships being the most vulnerable to disruption.
Which flowers I should plant in my garden to attract pollinators?
Insect pollinated flowers have several ways of attractive insects. These have large colourful petals, scent, nectar, hooked pollen to stick to insects and anthers that are inside the flower to ensure the pollen is transferred to its host.
Some plants emit ultraviolet light. Many insects can see this as we would see a normal colour. Ultraviolet light is the last to fade at dusk and these plants may have evolved to increase the chances of pollination. The evening primrose or Oenothera biennis is one such species.
What threatens the existence of insect pollinators?
Threats to pollinators include habitat loss, land degradation, fragmentation, pesticide use and non-native invasive species.
Habitat destruction, including loss of nesting sites, food sources and mating sites, is the main issue in the decline of wild pollinators. By ploughing, digging, cutting, paving and spraying unwanted vegetation (particularly wild flowers) we devastate the sites where wild bees make their homes. Flood irrigation saturates nests. Soil tillage, particularly in meadows, destroys nests and larvae.
The demise of native leafcutter bees in Manitoba (and the collapse of alfalfa seed production) was due to habitat destruction in the 1930’s and 1950’s. Wild pollinator populations have trouble establishing in areas of widespread monocultures because there is one kind of flower designed to bloom in a very narrow time window. Many annual crops do not depend on biotic pollination and provide little bee forage since they only bloom a few days each year. Many vegetable crops also do not require pollination, since the roots, stems or leaves are harvested, rather than the fruit.
Bees are guided by sight and smell. Yellow and blue coloured flowers are particularly appealing to bees.
Butterflies and Moths
Flowers pollinated by butterflies and moths have tube-like flowers where the insect can dip their long proboscis in to reach the nectar. The pollen in these flowers is large and sticky. Plant lilac and butterfly bush, and milkweed.
Vanilla seems to seduce butterflies above all other smells. Heliotropes, butterfly bush and ivy flowers are firm favourites too.
Some plants trick insects into pollinating them. Wallflowers, aubretias, nasturtium, mignonette and cabbages produce a mustard scent that contains pheromones. Large White butterflies land on these plants thinking the scent is from a potential mate and as a result, fertilize them.
There are actually more beetles on earth than any other living creature! The number of species alone is almost ¼ million. Obviously, many flowers are pollinated by beetles. These are normally white and produce strong odours. Examples of flowers that appeal to beetles include cow parsley (Anthriscus sylvestris), angelica (Angelica archangelica), Magnolia and dogwood.
You might also want to attract flies to your garden. Flies are also great pollinators. They are normally attracted to pungent smelling flowers that produce a similar smell to carrion, or rotting carcass. You can search Amorphophallus titanium online, or go to your local library, for a look at one of the world’s most interesting flowers.