Ants Can Farm

Ants tending scale insects on orange tree.

Have you ever wondered what in the world are ants doing on your plants?  Well, you might want to check their activities by following their trail.  It is likely that they are tending some aphids or scale insects somewhere on your plants.   This is the case with my orange trees that are in pots.   Hidden from my eyes are pests that are being farmed by the ants.  Slowly the aphids are sucking the blood out of my plants, and the ants feed from their exudates known as 'honeydew'.  Ants consume the honeydew as an important source of their nutrition.  The aphids and scale insects in turn have a greater survival rate and thus increasing their population.  As you can see, both aphids and ants benefit from this relationship but the plant is the victim.

Have you ever wondered how the ants farm aphids and scale insects? Here are some ways:

1. They protect them from their predators - For example, ants attack lady birds.
2. They prevent the proliferation of destructive microorganism (such as molds) by eating the honeydew.
3. They hunt for a favorable shelter and feeding area on their behalf.
4. They move the nymphs (young aphids or scale insects) to better parts of the host plants.

Ants cleaning/eating the wastes produced by scale insects.  On the background is a spider web.

It's a dog-eat-dog world out there.  The ants might seem very powerful in this case but there are also other living creatures that are "farming" them.  When I was scrutinizing my plants, I noticed that the ants were not the only indicator of the location of infestation.  If you look at the picture above, you can see a spider web that runs along the branch where the scale insects are.  Somewhere a spider waits for the ants to make a wrong move by stepping on its web.  The ants might be powerful to scare lady birds away but once they step on a sticky web, then they become a prey instead of a protector.

It turns out that spiders are our friends.