Ants and mealybugs often appear together on plants, leading many to wonder if ants prey on these small, white insects. The truth is, ants do not consume mealybugs. Their interaction is not predatory, but rather a cooperative relationship where both species benefit.
The True Relationship
The bond between ants and mealybugs is a classic example of mutualism, where ants “farm” mealybugs for a sugary substance known as honeydew. Mealybugs, sap-sucking insects, excrete this sticky, sweet liquid as a byproduct of feeding on plant sap. Ants are highly attracted to honeydew, a valuable and consistent food source.
In exchange for this nutrient-rich honeydew, ants provide protection to the mealybugs. They actively defend mealybug colonies from natural predators and parasites. Ants may even transport mealybugs to new, healthy feeding sites on plants, effectively expanding their “herd” and ensuring a continuous supply of honeydew.
Why This Matters for Your Plants
The presence of ants can worsen mealybug infestations on plants. By protecting mealybugs from their natural enemies, ants allow mealybug populations to increase significantly and spread more easily across plants. This unchecked growth leads to greater damage to the plant.
Mealybugs feed by sucking sap from plant tissue, which weakens the plant over time. This feeding activity can result in symptoms such as yellowing leaves, stunted growth, and premature leaf drop. Furthermore, the honeydew excreted by mealybugs promotes the growth of black sooty mold on plant surfaces. Sooty mold can block sunlight, hindering photosynthesis and compromising plant health and appearance.
Managing Both Pests
Effectively managing mealybugs often requires addressing the ant population as well, given their interconnected relationship. Controlling ants can allow natural predators of mealybugs to return and help reduce the mealybug numbers.
For ant control, slow-acting baits are a common approach, as ants carry the toxic substance back to their colony, helping to eliminate the nest. Physical barriers, such as sticky bands around plant stems, can also prevent ants from accessing mealybug colonies on the plant. Some natural repellents like vinegar, lemon juice, cinnamon, or peppermint can deter ants when applied near plants or ant trails. Regularly pruning branches that touch other structures or plants removes potential “ant bridges” to your affected plants.
Mealybug management involves several methods, depending on the severity of the infestation. For small infestations, individual mealybugs can be removed by dabbing them with a cotton swab dipped in 70% isopropyl rubbing alcohol. A strong stream of water can dislodge mealybugs from plant surfaces, which is a simple and effective physical removal method.
Insecticidal soaps are useful for soft-bodied pests like mealybugs, working on contact by disrupting their cell membranes. A typical solution involves mixing one teaspoon of dish soap per quart of water and spraying it thoroughly onto affected areas, including the undersides of leaves. Neem oil, a natural insecticide, can also be applied to disrupt mealybug feeding and reproduction, or to smother them. A common mixture is one to two tablespoons of neem oil with a few drops of dish soap per quart of water, applied every 7-14 days until the infestation subsides.
Preventative measures are also important; always inspect new plants for pests before introducing them to your existing collection, and consider quarantining new plants for a few weeks. Maintaining plant health by avoiding overwatering or excessive nitrogen fertilization can make plants less susceptible to mealybug infestations. For heavily infested plant parts, pruning and disposing of them can help reduce the overall pest population. In cases of severe and widespread infestations, discarding the entire plant might be necessary to prevent the mealybugs from spreading to other plants.