Ants usually do not eat scale insects as their main food source. Instead, many ant species feed on the honeydew produced by certain sap-feeding insects and may protect these insects from natural enemies.
This relationship is especially common with honeydew-producing soft scales. The ants gain a reliable food source, while the scale insects may benefit from reduced predation and disturbance.
For growers, the presence of ants on plant stems or branches can be an important clue when investigating a scale insect infestation. However, ants alone do not confirm that scale insects are present. Aphids, mealybugs, and other honeydew-producing pests can attract ants as well.
Understanding this relationship helps explain why some scale infestations persist after treatment. Effective management may require attention to both ant activity and the scale population, while preserving beneficial insects that naturally suppress these pests.
Why Do Ants Stay Around Scale Insects?
The relationship between ants and certain scale insects is primarily driven by food availability.
Scale insects feed on plant fluids using piercing-sucking mouthparts. Some species excrete excess sugars and other substances as a sticky liquid called honeydew.
Ants collect this honeydew as a food source. In some associations, they also defend the insects producing it against predators and parasitoids.
Honeydew Provides Food for Ants
Honeydew contains sugars that can provide energy for foraging ants. When a plant supports a large population of honeydew-producing insects, it may become an attractive feeding site.
Workers may repeatedly travel along stems and branches to collect these secretions. Their activity can make an infestation easier to detect, particularly when ants follow consistent trails into the plant canopy.
However, not all scale insects produce honeydew. Soft scales commonly produce noticeable amounts, while armored scales generally do not.
This distinction matters when interpreting ant activity. If ants are present but no honeydew-producing insects can be found, the source of their food may be elsewhere on the plant or nearby.
How Can Ants Protect Scale Insects?
Some ants actively tend honeydew-producing insects. Depending on the ant species and the associated pest, this behavior may include disturbing or attacking natural enemies, maintaining access to feeding sites, or moving certain insects to more favorable locations.
The result can be reduced biological control.
Predatory beetles, lacewings, and parasitoid wasps may normally help suppress scale populations. When ants interfere with these beneficial organisms, some scale populations may persist or increase.
The relationship is not identical in every ant and scale species. Some ants may ignore scale insects, and not every scale infestation depends on ant attendance.
For plant-health management, the key question is whether ant activity is contributing to the survival of the particular pest population.
Do All Scale Insects Attract Ants?
No. The relationship depends largely on the scale species and whether it produces honeydew.
Two major groups are commonly discussed in plant protection: soft scales and armored scales. They differ in their protective coverings, feeding biology, and production of honeydew.
| Characteristic | Soft Scales | Armored Scales |
|---|---|---|
| Common appearance | Often rounded or dome-shaped | Often flat, oval, or shield-like |
| Protective covering | The insect body may appear as a soft or waxy covering | A distinct protective cover is formed |
| Honeydew production | Common in many species | Generally absent |
| Attraction for ants | Often associated with ant activity | Usually less directly associated with honeydew-feeding ants |
| Diagnostic clues | Sticky leaves, honeydew, and sometimes sooty mold | Fixed scale-like covers, discoloration, and plant decline |
| Management considerations | Species identification and crawler timing | Species identification, crawler timing, and suitable treatment methods |
These are general characteristics, not a substitute for identifying the pest species.
Soft Scales and Honeydew
Soft scales can produce substantial honeydew when populations are high. The liquid may accumulate on leaves, stems, fruit, or surfaces below the infested plant.
Ants may gather around these deposits and repeatedly visit the insects producing them.
A combination of sticky foliage, ants moving along branches, and scale-like insects on stems is therefore a useful reason to inspect the plant more closely.
Armored Scales and Other Causes of Ant Activity
Armored scales generally do not produce honeydew. Consequently, their presence alone usually does not explain a strong ant trail.
If ants are active around plants with armored scales, inspect the same plant for aphids, mealybugs, soft scales, or other potential food sources.
Do not assume that every visible scale insect is responsible for the ants’ activity. Correct identification helps prevent unnecessary treatment and directs management toward the pest actually causing the problem.
What Are the Signs of an Ant-Scale Association?
Ant activity can provide an early warning, but it should be combined with direct inspection of the plant.
Look for the following signs.
| Observation | What It May Indicate | What to Check Next |
|---|---|---|
| Ant trails along stems and branches | A food source may be present in the canopy | Follow the trail and inspect leaves, shoots, and branch junctions |
| Sticky leaves or fruit | Honeydew-producing insects may be present | Check for soft scales, aphids, and mealybugs |
| Black coating on leaves | Possible sooty mold growth on honeydew | Inspect the upper plant surfaces and nearby branches for the honeydew source |
| Small, fixed bumps on stems or leaves | Possible scale insect infestation | Examine the insects with a hand lens |
| Repeated scale outbreaks after treatment | Treatment timing, coverage, reinfestation, or ant attendance may be involved | Review pest identification, crawler activity, treatment history, and beneficial insects |
Why Honeydew and Sooty Mold Matter
Honeydew is a sticky secretion. When it remains on plant surfaces, sooty mold fungi may grow on the deposits and form a dark coating.
Heavy sooty mold can reduce the amount of light reaching leaf surfaces and reduce the commercial appearance of ornamental plants or fruit.
However, sooty mold does not identify the insect responsible. Aphids and mealybugs can also produce honeydew, and ants may visit these insects instead of scale insects.
The correct approach is to locate the source of the honeydew before selecting a treatment.
How Should Ants and Scale Insects Be Managed Together?
When ants are actively protecting honeydew-producing scales, treating only one part of the problem may produce temporary results.
Ant management can reduce interference with natural enemies, while appropriately timed scale control addresses the existing pest population.
A practical integrated pest management (IPM) program should follow four steps.
Reduce Ant Access to Infested Plants
Start by identifying the routes ants use to reach the plant canopy.
Branches touching walls, fences, neighboring plants, or other structures can provide pathways. Pruning these connections where horticulturally appropriate may reduce ant access.
For trees and shrubs, physical barriers may also be useful. Commercial ant barriers or sticky bands should be installed according to their instructions. Sticky materials should not be applied directly to vulnerable bark, where they may cause injury or trap non-target wildlife.
Ant baits may be another option when a suitable product is available and legally permitted for the site. Placement should follow the product label and account for children, pets, pollinators, and other non-target organisms.
For a broader discussion of ant management methods, see ant control strategies for agricultural and commercial settings.
Protect Natural Enemies
Natural enemies can help regulate scale populations, particularly when ant interference is reduced.
Important beneficial organisms may include predatory lady beetles and parasitoid wasps. Their effectiveness depends on the scale species, environmental conditions, and the presence of other pest-management pressures.
Avoid unnecessary broad-spectrum insecticide applications that could eliminate beneficial organisms along with the target pests.
Where chemical treatment is necessary, consider its compatibility with the existing biological control program and follow all label restrictions.
Monitor the Scale Crawler Stage
The crawler stage is an important management window for many scale insects.
Newly hatched crawlers are mobile and generally have less developed protective coverings than settled individuals. This can make them more vulnerable to appropriately selected contact treatments.
Timing depends on the scale species, host plant, climate, and local life cycle. A treatment that works well against exposed crawlers may perform poorly against established insects protected by a mature covering.
Growers can monitor crawler activity by examining infested branches and leaves with a hand lens. In suitable situations, tape monitoring or inspection of affected plant material can help identify when crawlers become active.
The goal is to base treatment decisions on the actual pest stage rather than applying products on a fixed calendar without monitoring.
Choose Scale Treatments According to the Pest and Host
Treatment selection should follow accurate pest identification, the host plant, infestation severity, and the local product label.
Depending on the situation and permitted uses, management options may include:
- Pruning heavily infested plant material where appropriate.
- Horticultural oils or insecticidal soaps labeled for the host and target pest.
- Insect growth regulators or systemic insecticides where specifically permitted and suitable.
- Biological control and conservation of beneficial insects.
- Follow-up monitoring to determine whether the scale population is declining.
No single active ingredient is appropriate for every scale species, crop, or production system.
For more detailed guidance on identification, crawler monitoring, and treatment selection, see the POMAIS scale insect management guide.
Why Can Scale Infestations Return After Treatment?
A scale infestation may return for several reasons. Ant attendance is one possibility, but it is not the only explanation.
Treatment Missed the Vulnerable Stage
Many mature scale insects have protective coverings that reduce the effectiveness of certain contact treatments.
If the treatment is applied after most crawlers have settled, control may be incomplete. Additional eggs may also hatch after the initial treatment, depending on the species and its life cycle.
Monitoring and appropriate follow-up are therefore important.
Ant Activity Was Not Addressed
Where ants actively protect honeydew-producing scales, their continued presence may reduce the effectiveness of natural enemies.
If the scale population is treated but ant activity remains high, the ecological conditions that favored the infestation may persist.
This does not mean ant control alone will eliminate the scales. Both the existing pest population and the relevant ant activity need to be assessed.
Natural Enemies Were Disrupted
Broad-spectrum treatments may reduce parasitoids and predators that help regulate scale populations.
If the treatment suppresses beneficial organisms but leaves some scale insects alive, the pest population may recover.
An IPM approach should therefore consider not only immediate pest reduction but also the effect of the treatment on the wider plant-insect system.
The Original Pest Was Misidentified
Sticky leaves and ant trails are not exclusive signs of scale insects.
If the actual source of honeydew is an aphid or mealybug population, a treatment selected only for scale insects may fail to address the main problem.
Correct identification should come before product selection.
Frequently Asked Questions
Do ants eat scale insects?
Ants generally obtain food from the honeydew produced by certain scale insects rather than eating the insects themselves. Some ant species may prey on other insects under particular conditions, but tending honeydew-producing insects is the more relevant relationship in many plant infestations.
Why do ants protect scale insects?
Some ants protect honeydew-producing scales because honeydew provides a food source. By interfering with predators and parasitoids, ants may help certain scale populations survive. The strength of this relationship varies with the species involved.
Do all scale insects produce honeydew?
No. Soft scales commonly produce honeydew, while armored scales generally do not. If ants are active near armored scales, inspect the plant for other honeydew-producing pests before deciding on a treatment.
Will controlling ants eliminate scale insects?
Not necessarily. Reducing ant activity may help natural enemies suppress scale populations, but existing scales may remain on the plant. The need for additional treatment depends on pest density, species, plant damage, and crawler activity.
When is the best time to treat scale insects?
For many species, the crawler stage is an important treatment window because newly hatched individuals are more exposed than settled scales. The exact timing depends on the species, climate, host plant, and product label. Monitoring should guide treatment decisions.
A Better Approach to Managing Ants and Scale Insects
Ants and scale insects can form a relationship that makes certain plant infestations more difficult to manage. The ants obtain honeydew, while the scales may benefit from reduced pressure from natural enemies.
However, this relationship does not occur equally across all scale species, and ant activity alone is not enough to confirm the cause of a plant problem.
For growers and crop-protection professionals, the most reliable approach is to identify the pest, determine whether honeydew and ant attendance are involved, reduce ant access where appropriate, monitor crawler activity, and select treatments according to the host plant and local label.
For a commercial pest-management program, the objective is not simply to eliminate visible ants or remove the sticky residue. It is to address the underlying pest population while preserving useful biological control wherever possible.
A coordinated approach can improve monitoring, make treatment decisions more precise, and reduce unnecessary pesticide applications.
Post time: Nov-05-2025
