Managing Ants in the Garden: Controlling Aphid-Farming Ants

Ants rarely cause direct problems but create trouble by driving away predators of aphids and whiteflies—pests that excrete honeydew, a sugary sap ants love. Some ants invade houses during rainy weather; outdoors, nests grow larger in mild temperatures—a nuisance. Fire ants in the Southwest inflict painful stings and often build mounds in lawns or compost heaps.

To reduce ant food sources, keep aphid and whitefly populations under control. These pests sometimes live high in tree canopies; the only sign is a trail of ants marching up and down the trunk. Encircle tree trunks with sticky bands for several weeks to block ants. Pyrethrin kills ants on contact. Fire ants may relocate if nests are repeatedly drenched with boiling or soapy water.

For chemical control, place baited ant traps (sold for indoor use) in the garden. Spray carbaryl or diazinon for large infestations around patios. Drench or dust fire ant mounds with chlorpyrifos or diazinon.