Feeding a sugary solution to ants near the base of trees is an unlikely sounding but effective way of helping to control aphid populations in stone-fruit crops, growers heard at an event last month.
Professor Jerry Cross told the meeting, organised by East Malling Research Association (EMRA) and the Horticultural Development Company (HDC) on 24 April that the practice reduces the number of ants climbing up the trees, disrupting "ant-aphid mutualism".
Cross, who is programme leader for pest and pathogen ecology for sustainable crop management at the Kent research establishment, explained that ants feed off the honeydew that the aphids secrete and can also consume the aphids themselves as a source of protein.
The aphids, meanwhile, benefit from the ants' protection against predators and parasitoids, and are even transported to new shoots by the ants.
He said: "If ant protection of aphids is removed then the aphids are rapidly attacked and consumed, so the need for aphicide sprays is greatly reduced, often eliminated."
His research team looked at several different ways of disturbing the ant-aphid mutualism, including using bottle feeders and other types of sugary baits, as well as putting sticky cloth tapes on the tree trunks to exclude the ants from the trees.
Cross explained: "The results showed that providing sources of sugar to the ants was the better option. Exclusion (via sticky cloth tapes) will stop the ants but also earwigs."
He added that using the bottle feeders is impractical, he found, while durability is also a factor in selecting an appropriate bait - sugar cubes, for example, rapidly dissolve in the rain.
He recommended a 30 per cent sucrose solution stabilised with the sugar alcohol sorbitol, deployed just before blossom for four-to-six weeks.
Disrupting ant-aphid mutualism was one of experiments that were carried out as part of a five-year Link project, which started in April 2009 and finished this March (2014).
The aim of the project was to develop alternative, sustainable, biological methods for the main diseases and pests, including aphids, of stone fruit.
This is because a lack of alternatives has meant that this part of the top-fruit industry has had to rely heavily on pesticides.