Harvester ants eat seeds. At first thought, that might not be a good situation on a farm but they can have a significant impact on the number of weed seeds in a field. Westerman et al (2014) found that harvester ants destroyed 40-100 per cent of newly produced weed seeds. This included seeds of herbicide-resistant weeds. Harvester ants are found around the world, mostly in arid or semi-arid regions.
Farmers can recruit the ants’ weed control by reducing soil disturbance. Researchers from Penn State University found that no-till fields had larger ant nests and a more even distribution of nests than fields which were tilled. This means that no-till fields had more weed control helpers, which were spread more evenly throughout the field, which all results in fewer weeds.
Sources:
Barbara Baraibar, Joel Torra, Aritz Royo-Esnal, Jordi Recasens and Carles Comas. Harvester ant nest distribution depends on soil disturbance regime. Biological Control. Volume 128, January 2019, Pages 1-5
Joel Torra, Valentina Atanackovic et al. Effect of patch size on seed removal by harvester ants. Weed control. February 2016, Volume 56, Issue 1, Pages 14-21