Bees are nearly twice as good at killing off fungus on strawberries as mechanical sprayers, says an American team.
They planted three fields of strawberries and infected them with a common rotting disease called grey mould. They found that bees carrying fungicide to the crop on their feet slashed the number of infected strawberries by 72 per cent. Standard fungicidal spraying cuts infection by only 40 per cent.
The grey mould spores germinate mostly inside the flowers, says Joseph Kovach of Ohio State University. 鈥淪ince bees carry the fungicide specifically to the flowers, and right inside them, they are more effective than sprays,鈥� he says.
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Kovach used spores of an anti-fungal microorganism called Trichoderm harzianum. He put a tray of the spores outside a hive of honeybees next to the fields. The bees walked through this 鈥渇oot bath鈥� every time they left the hive.
鈥淥ur observations over the three-year test period indicated that there wasn鈥檛 a significant impact on bee or colony health,鈥� Kovach says.
鈥淭his is a very promising approach because it鈥檚 a very targeted approach,鈥� says Ingrid Williams of the Institute of Arable Crops Research in Rothamsted, Hertfordshire. Williams has been conducting similar experiments, using honeybees to deliver a fungus to control pollen beetles on oilseed rape. 鈥淲e also found that the bees were very effective,鈥� she says.
She points out that a constant temperature inside the hive of 30 掳C would kill most spores that found their way inside.
Since adult bees live for 30 days, Kovach recommends that honey farmers shouldn鈥檛 harvest the honey within a month of removing the fungicide tray from outside the hive.
Although he adds, 鈥淢ost of the honey that is produced at the time of the year when the strawberries are flowering is used by the bees. The extra honey we harvest is produced later in the season.鈥�
Using bees to treat crops with fungicide has not yet been approved in the US or Britain. But Kovach hopes that insects will soon be a common means of pest control.
鈥淚nsect delivery of biocontrol agents is preferable to spraying,鈥� he says. 鈥淭he insects are already in the field, they don鈥檛 use petrol or diesel, and they don鈥檛 contribute to soil compaction.鈥�
However, the weather might affect the bees鈥� effectiveness. 鈥淗oneybees don鈥檛 like to fly in cold, rainy weather,鈥� Kovach admits. 鈥淚f the bloom occurs during a long protracted cold, rainy spell, the bees won鈥檛 fly and deliver the goods.鈥�
His research was recently published in the journal Biological Control.