Aphid mystery solved

The clever folks at the Home and Garden Information Center have just solved a mystery for me, which was also a nice example of a deductive fallacy (on my part), so I thought I’d share it for general edification.

You may recall that last year I had a problem with aphids in my seed-starting process, which I’m pretty sure had to do with having taken plants outside during a warm spell and then being forced to bring them in again, along with some little juice-suckers that had hitched a ride. That took me forever to resolve (in fact I never completely did, but the plants finally got to stay outside for good), and stuck in my mind, so when I found aphids on my seedlings again a few days ago, I assumed the two events must be related – after all, I had never in all my years of seed-starting had aphids on my plants before last year, and so these must be the same aphids, or rather their descendants, miraculously preserved over many months in a moderately clean, definitely plant-free, and I thought pest-free room. (Once I got rid of the grasshoppers. Wasn’t my year.)

Well, I didn’t absolutely assume the aphids were related to each other, but I couldn’t figure out how else they could have gotten there. There had been no plants in the room between August, when fall transplants went out, and January, when I started some leeks and onions and also sweet potatoes from slips grown off my stored tubers (dug in September and October). In February I planted microgreens (since eaten) and also potted up a sprouting potato. (Both that plant and the sweet potatoes were being grown to support my root veggies talk, not to go into the garden.) And then I planted peppers from seed, and the resulting seedlings were where I saw the hordes of tiny green aphids a couple of days ago, along with a few on the sweet potato plants.

Some of the plants had traveled with me to MG events, but hadn’t introduced themselves to other plants there, and nothing had been outside for more than a few minutes in bitter to moderate cold. So where the heck could the aphids be coming from?

Potato aphid – BugGuide.Net

HGIC to the rescue! My little green not-friends are potato aphids, and they arrived at my house most likely on the potato from the supermarket that sprouted into my plant, or possibly on the sweet potato tubers I’d saved over the winter. I’d dumped the potato plant in the compost before I found the aphids on the other plants, but I suspect that’s the source. You know how we MGs are always telling you not to grow your potatoes from grocery store seed stock, because of disease potential? Well, here’s another good reason: they may bring pests with them, ones that are happy to suck on other plants besides the one that gives them their name.

The sweet potato plants have been discarded (all except one I potted up in a larger pot, that’s well away from the seed-starting room), but I’ve still got aphids on my tiny pepper seedlings that need to be dealt with, which I’m doing by: a) isolating the worst-affected plants to a sunny windowsill in another room (and planting more seeds for those varieties, in case they don’t make it); b) treating every plant on which I see aphids, as well as those on which I don’t, to a dose of soapy water, to be repeated as necessary; c) hand-squishing every bug I see. Carefully, because these are still very small plants – most don’t even have their first true leaves yet. I’ll let you know whether they win the fight. But I must get rid of the critters, because very soon I’ll have about a hundred other little seedings coming up.

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