Gardening: Beepocalypse now

A drone fly - also a pollinator. Photo / Rebecca Lees

Garden guru Steve Wratten looks at how to nurture our honey and bumble bees.

Beepocalypse. That's how an Australian journalist described the drastic decline in in bee numbers taking place in many parts of the world.

"CCD", or Colony Collapse Disorder, is on the lips of many beekeepers, especially in the United States. People still don't know why it's happening. It seems to be a combination of habitat loss from agriculture (fewer flowering weeds within the crops and their margins), a nasty mite called varroa, which attacks honeybee larvae in the nest and a nasty new group of insecticides called "neonics" - neonicotinoids is their full name.

Work in Britain, France and elsewhere has shown that ever-so-tiny quantities of these toxins on the bees' bodies make them lose their way back to the hive. Some countries have banned neonics - New Zealand hasn't.

Meanwhile, here, the malicious varroa mite seems to have wiped out most of our wild honeybee colonies. The managed hives seem to be doing well, at least for the moment, through the use of a mite-killing pesticide on the landing platform of the hives. In fact, the number of hives in New Zealand has reached a record of around 650,000, which seems to have over-compensated for the losses of the wild ones.

More than 60 per cent of the plants we (or our grazing animals) consume depend on pollination, so the first thing that will change if bee declines kick in will be fruit and vege prices.

What about our bumblebees? We have four types here (all introduced) but two are so rare we are unlikely ever to encounter them.

Early Pakeha settlers noticed they had difficulty growing lucerne and clover because the tongues of New Zealand bees were too short to pollinate these vital legumes. So they brought in the long-tongued garden bumblebee - but their entomological skills were poor, so three other species came with it, including the species that now dominates here, the buff-tailed or large-earth bumblebee.

Other insects pollinate too, of course; hoverflies for example. The introduced drone fly is in that group - it looks like a honeybee but it drones, rather than buzzes and, like all flies, has only one pair of wings.

So, what can we gardeners do to help our bountiful bees offset any future threats to their numbers? For bumblebees, providing shelter and food is the best approach. These bees cannot be "farmed", as honeybees can; in spring, bumblebee queens seek out places for their nest sites, in log piles, compost bins, under floorboards and in old mouse nests. We can make "pretend" mouse nests by making bumblebee motels - see p28 in bioprotection.org.nz/publications/biodiversity-farmland for the method. The occupancy rate of these refuges goes up year by year; a good thing, because most of our manicured gardens provide few nest sites for queen bumbles.

As for food, the four "wonder plants" I recommend for the honeys and bumbles are: rosemary, tree lucerne (tagasaste), the blue-flowered ceanothus and my old favourite, phacelia (there was a photo of the latter with my column on August 20).

Even better, sow seeds of a "pollinator blend" - available from some mail-order garden seed companies. Helping our bees is necessary and fun and here's a busy-bee quiz question: how can we find out whether it's warm enough for a bit of gardening? Answer: if you see honeybees on flowers it means it's above 10C.

Clever that, isn't it?!

Steve Wratten is Professor of Ecology at Lincoln University