The European Union has just banned three pesticides thought to affect the learning behaviour of bees. The two-year ban, which takes effect in December, is in response to a dramatic drop in bee numbers across the Middle East, Europe and the US. The pesticides are still in use in Australia.

The insecticides - imidacloprid, clothianidin and thiamethoxam, known collectively as neonicotinoids - affect the central nervous system of insects. Lab results have shown bees’ ability to learn is reduced by exposure to the pesticides, and that bee colonies suffer as a result.

But scientists working with pesticide companies say these results are not borne out in the field. Additionally, these pesticides are very useful for crops because they protect them very well and are relatively cheap and easy to administer.

Pollination in Australia

The use of these pesticides here should concern us. Honeybees pollinate human food crops worth around AU$4-6 billion annually in Australia. Much of our pollination is done by bees - not just honey bees but also native bees. We are talking about crops like broad beans, canola, sunflowers, but also lucerne and pastures, and many of our fruit trees.

Many crops are using the free pollination services provided by the bees, but others, such as almonds, use commercial bees.

Therefore any negative impact on the honey bee industry, either through honey production or as pollinators of Australian crops and pastures, has huge implications for Australia’s food security.

What do these pesticides do to bees?

We think these insecticides could be having an effect on bees. When they were introduced into the lab, honey bee numbers reduced considerably. At the moment there’s been no direct field evidence to say these insecticides are causing major problems, but there’s a strong potential there - too strong too ignore.

The pesticides don’t generally kill bees, but they reduce bee performance. Even though we don’t see huge numbers of bee deaths occurring, there are sub-lethal effects - that is a reduction in bee performance in pollination, and a reduced reproductive ability (that is, fewer offspring) and poor larval development.

Over a large area or large crop, any reduction in performance of a bee colony would have a major impact.

When the lab work has been taken into the field, we haven’t seen those impacts because of all the variables that take place. But because there has been such a big reduction in bee numbers due to colony collapse, the EU has set up this two-year ban. It’s really a precautionary ban.

Other threats to bees

In colony collapse, bees just disappear from their hives. Why they do it is not really well understood. There’s been an implication it is linked to pesticides but it’s not fully clear.

Bees come into contact with insecticides and, because they are social insects, they take the insecticides back to their hives, where they build up over time. Another problem is hives being infested with a pest called varroa mites.

Australia is considered varroa mite-free, but recently the Asian honey bee, which carries the mite, was introduced into Australia. Those bees, introduced via ship, were first detected in Portsmith, Cairns in 2007, and are now moving south.

A more variable climate, induced by anthropogenic climate changes, will also change the way bees behave, when they can forage and the quality of the nectar they have access to. More extreme temperatures will change the plant physiology, the pollen available to bees, as well as the bee physiology, bee behaviour, and the bee’s local environment.

Australia should consider banning these pesticides too. We use the same chemicals as the EU and we have the same reliance on bees for pollination. The EU is usually a long way ahead of Australia in terms of pesticide regulation. We don’t know what what potential these chemicals have to cause major problems. We haven’t got the science. But this is a great example of where the precautionary principle should be invoked.