Homeowners and gardeners who notice bare patches on their newly seeded lawns often face a puzzling mystery when the grass fails to sprout evenly. While birds or heavy rain may receive the initial blame, ants can be significant, yet often overlooked, factors in seed loss. These industrious insects are highly efficient foragers, viewing the freshly distributed grass seed as a concentrated food source. They rapidly carry the seeds away to be stored in underground colonies, rather than eating them where they lie.
Seed Consumption by Ants
Ants consume grass seed, but the damage to a new lawn is primarily caused by the systematic removal and storage of the seed. The main culprits responsible for this theft are species like Harvester Ants (Pogonomyrmex spp.) and the common Pavement Ant (Tetramorium spp.), which are widespread in suburban environments. These species are granivores, meaning their diet is centered on seeds, which they recognize as a valuable nutritional package. Grass seeds are high in fats, carbohydrates, and proteins, making them an excellent source of sustenance for the colony, especially for developing larvae.
Harvester ants, in particular, are known for their efficiency, often clearing large swaths of ground around their nests to collect and transport seeds. Grass seed is taken for its entire kernel content. The act of carrying the seed back to the nest removes it entirely from the germination zone, which is why lawns develop patchy areas.
The Motivation Behind Seed Harvesting
The primary motivation behind seed collection is long-term food security for the colony. Ants store the harvested seeds in specialized, dry chambers deep within their nests, known as granaries. For species like the Florida Harvester Ant (Pogonomyrmex badius), these granaries can hold hundreds of thousands of seeds, serving as a buffer against periods when foraging is limited, such as drought or winter. The volume of stored seed ensures the survival and growth of the insect population.
The high energy content of the seed kernel makes the effort worthwhile for worker ants, who are tasked with feeding the queen and the larval brood. Some harvester ants encourage the seeds to germinate using the damp conditions in their granaries. Germinating seeds become softer and easier for the worker ants to process and feed to the developing larvae, increasing the nutritional availability of the stored food. This drive to secure nutrient-dense food turns a newly seeded lawn into a foraging bonanza.
Protecting Newly Sown Grass Seed
Protecting a newly sown lawn from ant activity requires cultural and mechanical controls that make the seed less accessible and reduce the time it is exposed. One of the most effective strategies is to cover the seed slightly, since ants prefer to collect seeds lying exposed on the surface. Lightly raking the seed into the top one-eighth to one-quarter inch of soil, then covering it with a thin layer of peat moss or compost, makes it significantly harder for ants to locate and transport.
Proper irrigation is another technique that promotes rapid germination, which is the best defense against seed predation. Keeping the seeded area consistently moist encourages the seeds to sprout quickly. Once the seed has germinated, it is no longer an attractive food source for the ants. Timing the planting to avoid the peak ant foraging season, typically the hot summer months, can also reduce the risk of theft. Using coated grass seed can provide an additional layer of protection, as these seeds are often treated with a repellent or fungicide that makes them less palatable.