One of the common questions I get from customers is about what to do to control ants in their favourite citrus plant.
Sometimes, while tending to the citrus plants, people find ants moving up and down and would want to know what exactly could they do to keep the ants away. While the question is simple and would warrant a simple recommendation of a chemical, organic or otherwise, my answer usually takes a windy route.
The reason is that ants could occur due to different reasons. Unless we know the exact reason why ants are occurring, it would be difficult to recommend the specific control measure. The alternative would be to recommend any of the Broad spectrum pesticides (chemicals that kill a wide range of insects). However, they tend to have unintended consequences by allowing other secondary insects that weren't a concern before. Hence it is important to know what is causing ants to be present on your citrus in the first place. In most situations, ants do not feed on citrus directly.
First of all, there are fire ants and other ants species that form colonies in the ground and feed on the roots ending up killing your citrus trees. This rarely becomes an issue in container grown citrus. However, if they do, you could use any of the fire ant chemicals that are available in garden centres.
Secondly, there are leaf-cutter ants that take pieces of leaves to their colonies where they grow fungus which is used to feed the colony. Again chances are that you might not encounter these in container grown situations. If this does happen, you would need chemicals specific to leaf-cutter ants. If you ask for a leaf-cutter ant chemical, most garden centres would have them. On most packages, they would also have pictures of ants holding leaves, like in their names- leaf-cutter ants.
The third and most common situation where you would find ants is when you have other insect infestations that provide conditions beneficial for ants to thrive. Some insects like mealy bugs or scales that feed on the plant material end up pooping a sugary substance called honeydew. Ants feed on the honeydew and in return protect the insect from natural enemies like wasps. This sort of symbiotic relationship is not uncommon in insects where in exchange for the free food they provide protection from other species of insects or predators. The honeydew, in this case, would also cause fungus to grow, resulting in black leaves which are also aesthetically not pleasing. To control these ants, we need to control the insect that is hosting the ants on the plants. Once we eliminate the primary insect, the secondary insect, and the fungal growth can be controlled. We will look into mealybug control in another blog
Cheri Abraham, PhD