Attack of the Aphids!

By Paul James

Last Sunday morning I headed out to the garden to harvest potatoes, and as I walked past my tomato plants I noticed that they were covered with aphids. Rest assured, I didn’t waste time dealing with them, because aphids can do serious damage by sucking the sap (and the life) out of plants, and they can spread nasty diseases in the process. Worse still, they reproduce at a rate – and in a fashion – that’s truly mind blowing.

Consider this: Although aphids only live a month or so, a single female can potentially produce 600 billion descendents! That’s reason enough to declare war on them at first sight, because they survive – and thrive – by the sheer force of their numbers. It’s also why it’s often said that if aphids are good at one thing, it’s reproducing.

But it’s how they reproduce that’s so fascinating, because it almost always takes place without a male mate. In biology, this reproductive method is known as parthenogenesis (meaning virgin birth), and it’s a form of asexual reproduction that’s pretty bizarre, yet very beneficial if you’re an aphid.

Here’s how it works. Female aphids produce live offspring (again, without a mate) by basically cloning themselves. That’s kind of weird, I’ll admit. But it gets weirder, because each of the female’s offspring is born pregnant! And that’s precisely how they reproduce throughout most of the spring, summer, and early fall. So by skipping the time required for an egg to hatch and develop into a sexually (or asexually) mature female, their numbers increase at an astounding rate. They also don’t waste going out on potentially awkward dinner dates.

In fact, the only time female aphids take on a male partner is in the fall. And where do the males come from? Turns out a switch turns on late in the year that enables the females to produce a few male offspring. At that point, aphids reproduce sexually (way to go, guys!) so that the females can produce eggs that are capable of surviving the winter. And guess what? The eggs that hatch the following spring are 100% female, meaning a male aphid can’t produce sons. It’s crazy, right?

So much for the sex life (or non-sex life) of aphids. The big question now is, How in the world do you control them?

And thankfully, that’s fairly simple if you get a jump on things. Releasing ladybeetles will help, but one ladybeetle can only eat about 60 aphids a day, and I’m guessing there were at least a few thousand aphids on my tomatoes. That’s why I opted to use insecticidal soap, although I might just as well have used horticultural oil or Neem oil. I sprayed the plants thoroughly, especially the undersides of the leaves where most bugs tend to hide, and later that day the aphids were dead.

But one thing’s for certain – they’ll be back. If not on my tomatoes, then on something else in my garden. After all, there are at least 250 species of aphids that prey on plants.