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June 2013 Colony collapse

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Colony collapse

The alarming decline in numbers of bees, particularly honey bees, all around the world has provoked a huge amount of scientific research. The concern is not just about the supply of honey to spread on our toast. It's about the role bees play in pollinating plants. A decline in the number of pollinators has obvious ecological implications but also has a commercial impact because some agricultural crops are pollinated by bees. It also has an effect on your garden where bees are necessary for the production of many fruit crops and a few vegetables, such as broad beans.

While they are important for pollination, honey bees and bumble bees also have a negative impact in the garden. The majority of ornamental plants are grown for their flowers. The petals of a flower are insect-attracting organs. When a bee pollinates a flower, the job of the petals is done and they tend to fall off. So having plenty of bees can result in flowers staying in bloom for a shorter time. Some garden varieties, such as many Japanese flowering cherries, have sterile flowers and these stay in flower longer as they cannot be pollinated.

All the scientific research, over at least twenty-five years, has failed to come up with a definitive reason for declining bee numbers. It looks as though there are probably several factors at work, notably varroa mite infestation. But some researchers in both Europe and the United States are suggesting that one of the factors is a group of insecticides called neonicotinoids. Other scientists, particularly those paid by the chemical companies that make the insecticides, vehemently dispute their findings. The argument raged in the European Union earlier this year. Some countries wanted neonicotinoids banned, others didn't. The result was a compromise. Use of these insecticides was restricted for a two-year period to see what effect this would have on bee numbers.

Neonicotinoids are the only commercial insecticides to have been developed in the past fifty years. They were invented because they were thought to be environmentally safer than earlier chemicals, such as the organophosphates. As the name suggests, they are closely related to nicotine. Old books on organic gardening often contain recipes for home-made insecticides by soaking cigarette butts in water. The chemical companies took this idea and synthesised nicotine-related compounds to make powerful, systemic insecticides which are often used as seed dressings as well as in spot applications.

American research has implicated these insecticides, not just in declining bee numbers, but also in having a negative effect on birds and aquatic invertebrates. Rather alarmingly, another study showed damage to rats, particularly to brain development in young rats - rats are mammals, and so are we.

I like bees. I used to keep honey bees and the various species of bumble bee that inhabit my garden are a colourful and interesting component of its wildlife. The fact that my flowers may stay in bloom for a few days less is offset for me by good crops of apples and beans. So I hope that in a couple of years time, the EU experiment shows that we can control at least one of the factors causing their decline in numbers.


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