I bought a milkweed plant six months ago to replace something else that died by the side of our house. I heard that they were drought resistant and attracted butterflies. And although it has established fairly well, and seems to handle the summer heat, one other thing it seems to attract is aphids.
The first time I saw a cluster of aphids on my plant it made my skin crawl. They look like orange scales from some weird disease, which I guess they are. They almost killed the plant at one point until I started spraying them with neem oil, which suffocates them and turns them black. They're back in force now, though, and so I spray and wish for them to die.
Today as I was watering the plant I spotted a ladybug making its way along a leaf toward a cluster of aphids. These beetles are supposed to be natural predators of the aphid, and I've often wished that I had more of them in my garden. I considered buying some one point, although the purist in me feels that it would be more honest to attract them by planting the right kind of plants (and the malingerer in me has yet to research what type of plant that might be). Nevertheless, when I see a ladybug I get pretty excited.
This one was taking its time getting anywhere near an aphid. It walked from the stalk of the plant to the end of each leaf and back again like a Roomba--except biological-- covering every inch of the plant. It was taking so long that I decided to assist by holding my finger in front of it until it climbed aboard and then whisking it over to where aphids hang out. After disembarking it walked up to an aphid, sort of reared up, like it had just run across another dog on a leash, and then turned around and walked the other way, Roomba-style. After it flew off I got out the neem oil.
Even though they suck the sap out of my plants and make me want to commit insecticide, I have to admit that this is a little bit hypocritical. I planted a passion fruit vine across the garden, also to attract butterflies, knowing full well that the larva would decimate the leaves of my plant. But some pests drive you to ignore your principles.
Speaking of which, the aphids in my yard are pretty cozy with the ants that tromp around like they own the place, which makes me think they're up to no good. I don't trust the ants. Sometimes I see them on a tree I just planted I wonder what they're up to. I lost a Channel Islands Ironwood tree last year because, apparently, the ants that I had noticed for some time climbing up and down its poor sapling trunk were "farming" scale bugs. I'm not sure if the ants caused them to reproduce any faster, and consequently drain the young tree of its sap any faster than they otherwise would have, but they were definitely complicit. As with aphids, ants protect these bugs so that they can "milk" them for the honeydew they excrete.
The one piece of information I've uncovered on this topic that gives me any satisfaction at all has to do with butterflies, which I love, pulling one over on the ants. Apparently there is a species that as a pupa excretes a pheromone that makes the ants think it is one of them, kind of like cats are said to do with people. They then take it back to their nests where it eats their larvae, until it forms a cocoon and turns into a butterfly. At that point the butterfly must crawl to the opening of the nest in order for its wings to open up. During this time it's susceptible to attack because it no longer has the pheromone. It has to get to the opening of the nest and fly away before the ants catch it and tear it to shreds, kind of like the Millennium Falcon exploding from the Death Star.
I know that all creatures have a purpose in this world, but I find myself thinking about this scene and imagine it playing out like in the movies, complete with the total destruction of the nest. The day that happens I'll be there to watch my butterfly friend take wing, shaking my hand in the air, brandishing a bottle of neem oil at the now-defenseless aphids.