As tiny and mobile hunters, forest ants are protecting the fruit orchards of the future by devouring the pests that can destroy a good harvest of pears and apples.

Researchers from Aarhus University Denmark are transporting several ant nests from Danish woodlands and moving them to apple orchards in the hilly lowland peninsula of Djursland.

The mission is for ant workers to help increase the production of organic fruit. Forest ants are among the first insects to start work as spring temperatures begin to warm up the environment.

The insects are hungry and go hunting en masse where they find and eat pests, including unwanted larvae that limit apple tree growth and production. Larvae can eat enormous amounts of leaves and buds, thus seriously reducing the amount of fruit the tree will eventually produce.

"We have seen that forest ants eat winter moths which are the prime enemies of apple trees," says senior researcher Joachim Offenberg, from the Department of Bioscience at Aarhus University.

"Winter moths eat apple tree leaves in spring and cause great damage."

This small pale green moth larva appears while it is still cold and where there are few predators to eat them. Their natural predators, the Great titmouse and other birds, are still nesting in early spring, while other predatory insects remain in hibernation.

Without an army of predatory ants, these moths can go on the rampage and cause severe damage to orchards.

"We will move a large ants nest from a pine forest and establish a number of smaller nests each with their own queen around the apple orchards.

"The forest ants need pine needles to build their nests, so we will provide extra pine needles in the orchards."

Via bacteria living on their bodies and through their own glands, the ants secrete antibiotics, including mycotoxins.

"We hope that the ants production of mycotoxins may combat, among others, scab, a fungus that destroys the apples."

Scientists have seen how the number of diseases on wild trees increases significantly if you remove the ants from part of the tree.

Organic fruit in short supply

As ants move around the apple trees, they drop feces and urine which is also beneficial to the plants. They secrete the nitrogen compound urea that is absorbed by the plant leaves and trees are fertilized with nitrogen, stimulating growth.

Danish organic fruit is in short supply and producers face tough challenges to reach a robust and economically viable production, while avoiding chemical insecticides.

This experiment of moving ant colonies directly into apple and pear orchards could prove to be a game-changer, according to the researchers.

This project is part of the Organic 2.2 programme, coordinated by the International Centre for Research in Organic Food Systems (ICROFS) and funded by the Danish government's Green Development and Demonstration Programme (GUDP).

Related story: Danish review claims ants control pests as well as pesticides

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