Walking aphids can partake in within-field dispersal to distant plants

The ability of herbivorous insects to move to distant plants critically affects their spatial distribution and spread across habitats. Aphids (Hemiptera: Aphididae), some of which are major pests and vectors of viruses, have two modes of dispersal: Flight of winged aphids (alates) to distant plants and walking by wingless aphids (apterae). The dispersal ability of individual aphids has far reaching consequences regarding their spatial distribution since a single aphid can rapidly establish a new colony via parthenogenetic reproduction. We show that walking wingless aphids have an important role in aphid dispersal to previously unrecorded distances. We marked wingless pea aphids (adults and nymphs) with fluorescent powders and traced their inter-plant movement in distinct seasons, a method that allowed us to record the actual dispersal abilities of individual aphids. In a semi-natural habitat, aphids were able to walk and reach plants up to 13.5 m away from the release point in 7 h, much more than previous assessments of aphid ground movement capabilities. In a commercial alfalfa field, dispersal distances were shorter, but a few aphids dispersed up to 7 m from the release point. The walking distances of aphids were affected by age (adults vs. nymphs) and by ambient conditions. The aphids' walking abilities may have strong implications for their spatial distribution in natural habitats, for their levels of infestation and damage and for virus epidemiology in agricultural fields, and should be incorporated in models of aphid and virus dispersal.