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Protect Our Food: Be Pollinator Friendly

Pollination is essential for the production of many of our food crops as well as the crops that feed the animals we eat. It is estimated that in the United States, pollination contributes in the order of $20-30 billion of economic value to agriculture per year.

Pollination of plants can occur by a variety of mechanisms including self pollination (peas and beans are a good example), wind pollination (grain crops are a good example) and pollination by insects and other animals. Around 90% of all flowering plants are pollinated by pollinators. Bees are one of the most important pollinators. Many crops such as almonds and avocados, rely entirely on bees for flower pollination and thus fruit and nut production. Many others rely heavily on bees for their productivity (apples and blueberries for instance attribute around 90% of their pollination to bees). Nearly one third of all agricultural pollination is accomplished by honeybees. This is quite astounding when you consider the amount of grain (which is wind pollinated) we eat.

Bees are in decline though - both wild and captive populations. As an example, it is estimated that in the US 10 million commercial beehives have been lost since 2006. Many other pollinators, such as native bees, wasps, butterflies, moths, flies, birds, beetles and bats, have suffered losses as well. Though bees have probably been effected the most. Humans have contributed to pollinator losses through a variety of actions including destroying habitat, poorly managing the land (especially home gardens and farm land), using pesticides and introducing exotic species of plants and animals and their associated exotic pathogens. As gardeners, our pesticide usage, plant choices and attention to plant health probably has the biggest impact on pollinators.

Pesticides and Pollinators

Pesticides can kill bees and many other pollinators directly. Carbamates, organophosphates, synthetic pyrethroids, chlorinated cylcodienes and neonicotinoids are all classes of chemicals that are acutely toxic to bees and will kill them if they are exposed to the chemicals.

Some pesticides however, can kill or negatively affect bees indirectly by interrupting their memory so they cannot find identified food sources or worse, their hives; interrupting their foraging ability; or interfering with their reproduction. Studies have also found a correlation between agricultural pesticides and increased infection with viruses. Low doses of many pesticides can cause these sublethal effects but the same pesticides can often kill a bee outright if the concentration is sufficiently high.

There are many strategies used to prevent such effects. As an example, spraying harmful pesticides in the morning and evening, when honey bees are less active, is considered by many to reduce the negative impact of such chemicals on bee populations. This strategy fails to take into account the foraging habits of other bees though and so native bee populations can be decimated by gardeners who are trying to do the right thing.

Combinations of different pesticides can also have greater effects on pollinators than if the individual chemicals were applied in isolation. Furthermore, herbicides (pesticides designed to kill plants) can affect bee populations by reducing the number of flowering plants and thus reducing food supplies.

Perhaps the worst pesticides are those that are classed as systemic pesticides. Such chemicals, when taken up by a plant, can travel around the plant to all of the tissues including the leaves, flowers, roots, stems, pollen and nectar. Once inside a plant, the chemicals remain active for many months, even years. Likewise, the chemicals remain active in the soil for extended periods of time and in water too if they travel into local waterways. Neonicotinoids (or neonics) are the most common systemic pesticides. Many systemic pesticides are known to be harmful to pollinators. Neonics for instance, are known to be harmful to bees and there is growing concern about their impact on other species, such as birds. As a result, if a systemic pesticide such as a neonic is sprayed on a seed, the resulting plant will harbour toxic chemicals in its pollen and nectar and so any pollinator that visits the plant will then be exposed and suffer the negative consequences.

The rates of pesticide usage are high. As an example, over 90% of corn in the US is sprayed with systemic pesticides. Yet there are significant negative consequences for ingestion of contaminated corn by some animals (a single corn kernel coated in a neonicotinoid can kill a songbird if ingested according to the The Impact of the Nation’s Most Widely Used Insecticides on Birds by Pierre Mineau and Cynthia Palmer) and the effects of systemic pesticides on beneficial insects pollinators have not be studied in depth.

Colony collapse disorder (CCD)

CCD is a disorder that is having a significant impact on honeybee populations as worker bees disappear, never to return to the hive. The cause of the CCD is currently unknown but research suggests that pesticides likely play a role in the disorder.

Varroa Mite

Most living organisms can be attacked by other organisms and bees are no exception. A variety of mites and other organisms attack bees but the varroa mite is perhaps the biggest such threat to bee populations at the moment. The mites feed on bee haemolymph (the equivalent of sucking a bee's blood - think of them as vampire mites) and at the same time, infect the bees with a virus that results in bees being born flightless. Such bees die shortly after they 'hatch'. While varroa mites are a threat in and of themselves, there is some evidence to suggest that they also contribute to CCD.

Unfortunately there is also growing evidence to suggest that a range of pesticides can compound the effects of varroa mite infestation by making bees more susceptible to the virus transmitted by the mites as well as other viruses. Of particular concern is the fact that pesticides used to treat varroa mite infestations have been shown to increase bee susceptibility to the virus transmitted by the mites until all the mites can be killed. Thus, if the mites become resistant to such pesticides, it may become impossible to treat varroa mite infestations without decimating bee colonies. Furthermore, there is evidence to suggest that some pesticides (that are used to treat other pests like aphids) increase the hatch rate of varroa mites and help them to survive.

What to do to Protect Bees and Other Pollinators

If you are concerned about the decline in bee numbers and the effects of pesticides on other pollinators, there are a number of steps you can take to reduce your impact.

  1. You can stop using pesticides in your garden and home (indoor pesticides can kill bees too). This of course includes synthetic chemicals that you can buy but it also includes organic chemicals that you might purchase or make at home. Pyrethrum is a great example. It can be purchased at many nurseries and DIY shops but it can also be made at home from home-grown pyrethrum flowers. This makes it an organic product (unless the purchased product contains non-organic ingredients) but it is still harmful to bees. If you want to stop using pesticides, a gradual shift to alternatives such as companion planting and crop rotation can help you combat pests. Continuously improving your soil will also allow you to grow healthier, more pest resistant plants (pests usually attack unhealthy plants first which are also likely to be more heavily affected by any pest attacks).
  2. You should also evaluate the sources of the seeds and plants you buy. If you purchase plants or seeds that have been treated with pesticides, particularly systemic pesticides, your garden will still be full of plants that can harm pollinators. To combat this, try to find nurseries that sell certified organic seeds and plants as these must be free of synthetic chemicals. Some organic pesticides, such as neem, are systemic chemicals but none are persistent (they do not hang around for a long time) so plants or seeds treated with such chemicals prior to purchase they should do relatively little damage once they're in your chemical free garden. Also, any seeds saved from such plants shouldn't contain any pesticide residues unless you purchased a plant that had been sprayed and was close to flowering. You might be able to find a nursery that sells completely chemical free products and this would be ideal but it's rather unlikely in most areas, especially in the developed world.
  3. Start saving your own seed. If (as I've alluded to above) you purchase organic seeds and plants and don't use chemicals, you should be able to save uncontaminated seed to replant.
  4. Plant lots of flowering plants and aim to have plants in flower all year round. This will provide lots of food for pollinators. Provide some shallow water trays as well as many pollinators need to take in lots of water to survive.
  5. Provide habitat for pollinators. This might include spiky bushes for small birds and mud bricks and logs with holes drilled into them for bees and other insects. If you can, keep any trees that have hollows in them as these can provide great homes for many animals. 

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