Myrmelachista

Myrmelachista is a genus of ants within the family Formicidae (order Hymenoptera) that can cause significant agricultural damage. Unlike typical soil-dwelling ants, many species in this genus are arboreal and strictly associated with living plants, where they create nests by excavating galleries within the stems, twigs, and trunks of trees.

The biology of these ants is deeply intertwined with their habit of farming trophobionts, such as aphids, scale insects, and mealybugs. The ants protect these sap-sucking pests from natural predators in return for honeydew, a sugary substance secreted by the insects. This relationship creates a double threat to the plant, combining physical structural damage with increased infestation by other sap-sucking pests.

This pest primarily affects woody crops, including coffee, cocoa, and various citrus species, as well as a variety of ornamental trees. By boring into the wood, the ants weaken the structural integrity of the plant, leading to stunted growth, branch dieback, and in extreme cases, the total death of the host plant due to secondary infections that enter through the exit holes.

The life cycle begins when a queen colonizes a suitable cavity in the tree. The colony grows slowly as workers expand the internal tunnel network. Because the ants spend most of their time inside the plant tissues, they are well-protected from environmental changes and many traditional contact pesticides, which necessitates a more specialized approach to their management.

To effectively manage and suppress Myrmelachista populations, agriculturalists should consider the following strategy:

• Implementing regular inspections to identify early signs of colonization.
• Sanitary pruning of infested branches and stems to physically remove the nesting site.
• Deploying slow-acting bait stations that allow workers to carry toxic substances back to the queen.
• Applying sticky barriers or grease bands to prevent movement between the ground and the canopy.
• Targeting the associated aphids and scales to reduce the availability of honeydew, effectively starving the colony.