Friday, May 15, 2009

Ant Farmers, Aphid Farms

Sometimes I think we are ant farmers more than anything else--they certainly seem to comprise the largest population of "livestock" on the farm, by sheer number of individuals. They make a vital contribution to the health and well-being of the farm by constantly building aeration and drainage structures. They clean up weed seeds and dead insects and all sorts of stuff.

But THEY are farmers, too. Or maybe ranchers or dairy operators would be more specific.

Many folks are familiar with the phenomenon of ants "farming" aphids. The ants feed on the "honeydew" secreted by the aphids as the aphids feed on the host plants. In turn, they manage and protect the aphids. It's an interesting relationship, but not so happy for the vegetable farmer if the host plant happens to be a valuable crop.

In the past couple years, I've become aware of a new aspect of ants "farming" aphids that I had not realized, perhaps because I don't spend a lot of time pulling dandelions. The sheep eat them out of the yard and pasture, and I tend to tolerate the few that grow in the garden. But the garden population has increased in the past few years, and we have a real bumper crop this spring. That's not all a bad thing, since they are a nutritious and tasty salad green or cooked vegetable when expertly selected--a skill I've been honing for years.

But today, I had to pull a bunch out of a fallow bed where I wanted to put in some perennial herbs. Several of them had ant hills around them--our classic small golden-red ants. When I pulled those dandelions, the long tap roots--some over a foot long--came up easily due to the loose soil of the ant nests. And those roots were covered with white specks--aphids, growing underground on the dandelion roots, up to 5 or 6 inches below the soil surface. With ants tending them.

No hard science here, but it sure looks to me like the ants have created artificial underground living space for the aphids, where temperatures and other conditions are more constant than above ground, and the aphids (and their keepers) are protected from predators, wind, rain, etc. Sort of a CAFO (Confined Animal Feeding Operation--i.e., feedlot) for aphids. Without the drainage and aeration provided by the ants, the root zone would be inhospitable for the aphids. The roots provide all the food the aphids need.

I think I've seen these ant-run "aphid farms" on other plant roots, but not very often and not at this early season. That makes sense--the dandelion certainly stores a lot of nutrients in its roots, and pushes up leaves to replenish those stores early in the spring.

Needless to say, the dandelions seem to be unperterbed by their status as feed supplier to these extensive underground CAFOs. It actually looks like an incredibly sustainable farming system. I'll be watching and pondering this phenomenon more closely, looking for the lessons it has to teach us about making our own farming more sustainable.


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Cicero Sings said...

'I've been pulling dandelions and have noticed the ants at their base so I'm very interested to read your findings!