When black garden ants go from nuisance to pest

Black Ants in gardenI’m never quite sure where the ‘black’ or the ’garden’ elements relate to Lasius niger. In our garden these ants look more of a very dark brown and are to be found under the patio slabs, in the flower pots, creating small piles of earth along the edge of the lawn or most often as not, attempting to tunnel their way into our kitchen!

Out of about 11,000 ant species worldwide there are about 50 that frequent the UK. The common black garden ant is one of the most robust and prolific to be found on our shores. Colonies can grow to around 15,000 workers, but the average is between 5,000 to 7,000 ants.

During the winter an ant colony will remain dormant. Only when the weather starts to warm will the worker ants set out to forage. Garden ants will eat a variety of food, from nectar, soft fruits and small insects to honeydew from aphids and anything sweet and sugary they can find in the kitchen.

As the queen lays more eggs and the colony grows over the early summer months, worker ants will forage further afield to find new food sources. This will often bring them inside properties. They will also use these explorations to test new areas to see if they are suitable new nests the following spring. Such explorations can be very extensive. We returned from holiday once, to discover a trail of ants marching down the hallway into the kitchen. They had burrowed a tiny tunnel, through the mortar between the brickwork and the plasterboard wall!

When worker ants find a new food source they will leave a pheromone path (a trail of chemicals) that other ants will follow to the food from the nest. At this point, as garden ants are marching into the cupboards and all over the food they go from a nuisance to a pest.

How to deter ants from entering:

  • Clean up food & liquid spillages, using disinfectant will help remove the pheromone trails ants follow
  • Sweep up food crumbs from under kitchen appliances & units, removing any easy food source
  • Store foods in airtight containers wherever possible, to protect food & deny ants access
  • Block off entry points by sealing all cracks & crevices around your doors and window frames.

Usually prevention is enough to deter garden ants from entering a property. However if the nest is too close to a building or inside the wall voids, garden ant control will need to be done by qualified professionals. As destroying the nest, eggs and queen, rather than just the foraging worker ants is much more difficult to achieve.

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