Landscape - Ants, Honeydew Producing Insects, and Insect Predators

The following is a good article on honeydew producing insects, the ants that protect them, and the predators that feed on these insects and the interactions of all three.

ANTS & HONEYDEW PRODUCERS vs. PREDATORS: Various pests such as aphids, soft scales, mealybugs, and whiteflies are plant feeders that insert their piercing-sucking mouthparts into vascular tissue (phloem) to remove plant sap from leaves or stems. Since phloem sap is not nutrient rich in proteins, plant pests must withdraw large quantities to maintain growth and reproduction. As a result, these insects must also expel copious amounts of unwanted waste called honeydew. The predigested honeydew still contains a lot of sugary carbohydrates and is valued by ants, wasps, bees and other vespids as a food source. The honeydew is often easily observed as a clear, shiny and sticky material on foliage. The honeydew usually darkens over time as a black sooty mold fungus grows on the liquid droppings.

Numerous predators and parasitoids including ladybeetles, lacewings, flower flies and wasp parasites typically attack and consume honeydew-producing pests. Carpenter ants and other colony ant species have waged vicious wars for “eons” against predators of honeydew producers. Certain ant species will expend a lot of energy and effort to protect honeydew producers and prevent effective biological control. As a result, to help restore the predator vs. prey balance in the landscape, it may be necessary for the pest manager to intervene and seek out ant colony locations to apply controls.

Ant protecting aphid colony. Photographer - Kent Loeffler © Cornell University, Dept. of Plant Pathology, 2005

Information from Steven K. Rettke, Ornamental IPM Program Associate, Rutgers University