Pineapples (Ananas comosus) are typical edible landscaping plants in U.S. Department of Agriculture plant hardiness zones 10 through 11, though they are gaining popularity since indoor denizens as well. Pineapples are generally hardy and also have few pests, but do suffer from scale insects and mealybugs, both sap-feeding insects which attract ants.
Argentine ants (Linepithema humile), the most common ants in the house and garden, are mainly sugar-feeding insects that live in shallow mounds from the dirt. Sometimes infesting houseplants or finding their way in through tiny cracks in homes, these 1/8 inch long, dull brown ants are not dangerous to humans but can be ascertained nuisances once they’ve located an ample food supply.
Although ants may be drawn to over-ripe pineapples, it’s considerably more likely they are farming scale insects or mealybugs which are feeding on plants. These insects excrete a sticky, sweet substance called honeydew that ants will go to great lengths to procure. When ants find a colony of scale or mealybugs, they’ll protect these nuisance insects, even moving them about from plant to plant to help increase their numbers.
Pineapples in pots may host ants as permanent guests in their land, especially if the ants are feeding on honeydew produced by insects living on the plant. If you discover that ants are living on your own potted pineapples, take the plants outside and submerge them into the very top of their pot for approximately 20 minutes in a bucket of water laced with 2 tbsp of insecticidal soap each quart of water. This will kill all the ants living in the pot without damaging the plants. Treating the leaves of the pineapple for sap-sucking insects is crucial to keeping ant control — spray them using the undiluted insecticidal soap you used to kill the ants.
Ants in exterior pineapple plantings can be more difficult to handle, but it’s not impossible once sap-feeding insects have been controlled. Argentine ants easily accept sugar-based ant discharges when they are put on each side of their paths. Check these bait stations regularly so the food supply doesn’t run out as worker ants carry the poisoned bait back to their nests, slowly poisoning the entire colony. Any pineapples planted in containers or raised beds can benefit from an application of a sticky barrier.