The sight of ants crawling over strawberry plants is concerning for any gardener. While ants are not usually the primary threat to the fruit, their presence signals an underlying issue that can jeopardize the health and yield of the patch. Protecting strawberries requires a multi-pronged strategy, moving from immediate physical barriers to long-term colony eradication and pest management. This approach ensures the fruit remains clean and the plants stay healthy.
Why Ants Are Invading Strawberry Plants
Ants are drawn to strawberry plants by a readily available food source other than the fruit itself. The primary attraction is honeydew, a sugary liquid excreted by common garden pests such as aphids, mealybugs, and scale insects. These pests feed on the plant sap and leave behind the sticky residue.
The ants act as ‘shepherds’ to these pests, protecting them from natural predators like ladybugs in exchange for the honeydew. They even move the honeydew-producing insects to new parts of the plant to ensure a continuous food supply. By protecting these secondary pests, the ants indirectly cause damage as the aphids and scale deplete the plant’s resources, leading to stunted growth and curled leaves.
Immediate Physical Protection Methods
When ants are present, the first step is establishing a non-toxic physical barrier to block access. A fine layer of food-grade diatomaceous earth (DE) can be dusted around the base of the plants and along ant trails. DE is composed of fossilized diatoms; its microscopic, sharp edges cut the ants’ waxy exoskeleton. This abrasive action causes the insects to dehydrate and eventually die.
For plants in containers or raised beds, a water moat or barrier is an effective physical deterrent. Also, ensure the strawberry patch does not have “ant bridges,” such as leaves or stems touching the ground or adjacent structures. DE must remain dry to be effective, requiring reapplication after watering or rainfall. When applying DE, use a fine dusting device and avoid creating large clouds of dust, which can be irritating if inhaled.
Eradicating the Ant Colony
Eliminating the entire ant colony, including the queen, is necessary for a permanent solution. Ant baiting is the most effective long-term method, as workers carry the slow-acting toxin back to the nest, infecting the queen and larvae. Unlike contact sprays, which only kill foraging ants, baits target the source of the infestation.
Commercially available ant stakes or liquid bait stations are recommended near food crops, as they contain the toxic substance and prevent direct contact with plants. Place these stations along known ant trails leading away from the strawberry plants, not directly in the patch. Many effective baits use a small concentration of boric acid mixed with a sweet attractant.
The low concentration of boric acid is crucial; a high concentration will kill the worker before it returns to the colony, defeating the bait’s purpose. Boric acid is toxic to plants in high doses, so containing the bait prevents soil and plant contamination. Monitor and replace the bait regularly, as colony eradication can require several weeks.
Controlling Secondary Pests
Since ants are primarily on the plants for honeydew, removing their food source is the ultimate strategy for long-term control. Honeydew-producing pests, like aphids and scale, must be managed directly to eliminate the ant incentive. A targeted application of insecticidal soap or neem oil is an organic option that controls these soft-bodied insects.
A strong jet of water from a hose can also dislodge small populations of aphids from the leaves. This must be repeated regularly, often every few days, to keep populations low. Introducing natural predators, such as ladybugs or lacewing larvae, provides biological control of the aphids. By eliminating the pests that produce the sugary honeydew, the ants will lose their motivation to visit the strawberry patch and forage elsewhere.