The presence of ants is known to reduce biological control of aphids due to them having a mutually-beneficial relationship.
Ants protection from predators in exchange for the honeydew aphids produce while feeding on plants – but new research suggests that providing alternative sugar sources could provide a low-tech solution for growers.
The study, led by Csaba Borbély and carried out in Hungarian apple orchards, showed that by offering sugar solution in bottles or agar jelly cubes, numbers of the ant Lasius niger tending aphids decreased, while control of the aphid species Aphis pomi and Aphis spiraecola increased.
The simple approach allows natural enemies of aphids such as ladybirds, lacewings and parasitic wasps greater access to attack aphid colonies.
A sweet distraction
The scientists used a concentration of 300g sugar for every litre of water – and the solution presented in bottles proved more effective than the agar jelly for attracting the ants away from aphids, the work suggested.
“The use of sugar-feeding tactics to alter ant behaviour should permit reduced pesticide use in apple orchards, whether to control aphids or other pests that might serve as prey for ants, and is fundamentally compatible with biological pest control in apple orchards,” Borbély wrote.
Practical limitations
The fact that the presence of some aphids is tolerable in green apple orchards means that the use of either sugar source could remove the need for pesticide applications in such settings, they said. But despite the success of the approach, there are practical limitations that need to be addressed.
For the technique to be effective, a bottle dispenser would be required on every tree, and would need to be inspected and refilled when needed. This would add to labour demands. Agar jelly cubes are easier to use and a more sustainable option, but their reliability is affected by drying out, being diluted by rain or eaten by animals.
“Elaborating other practically manageable and reliable operating dispenser types and/or the combination of the sugar dispensers with other ant-attractant chemicals…are interesting topics for future studies,” Borbély added.
You can read the full paper in the journal Agriculture.
