Slippery paints: Eco-friendly coatings that cause ants to slip

Many insects are considered to be pests and can be serious threats to buildings. Insecticides represent an effective way to control pest insects but are harmful to the environment. As an eco-friendlier alternative, we have formulated waterborne, organic paints which provided a slippery physical barrier for leafcutter ants (Atta cephalotes) on vertical surfaces. Different paints were produced by varying the Pigment Volume Concentration (PVC) and amount of TiO2 and CaCO3 particles, and characterised in terms of contact angles, surface roughness and scrub resistance. The paints' slipperiness for A. cephalotes ants was evaluated in climbing tests on vertical paint panels (by recording the percentage of fallen ants). Two main factors reduced the insects' attachment to vertical paint surfaces: (1) the PVC: in paints above a critical PVC, more loose particles detach from the coating and thereby reduce insect attachment; and (2) the type, dimensions and shape of solid particles: CaCO3 particles detach more easily from the paint than TiO2, probably due to their larger size and platelet shape. Paints formulated at PVC 70 and containing 20 wt% CaCO3 showed the best performance in terms of slipperiness, as well as providing good scrub resistance.