Are my seedlings at risk now that I have obvious pests in my greenhouse?

Asked March 2, 2015, 11:11 AM EST

I have a wonderful new greenhouse. It's about 16 x 10, glass, heated to 55 degrees and fairly successful. The first picture is of my second winter season of lettuce. The second two pics are of my new aphids and white (flies?) which are invading. I think I know what I need to do, but want your advice. Should I: 1) Throw out all the lettuce bins (not a huge loss, as I've eaten it all fall and winter). 2) Let the bin soil freeze and thaw a few times outside to kill the pests. 3) Look carefully for other plants being infested and remove them. QUESTIONS: Do I have to do any additional cleaning of the greenhouse? Is there hidden infestation which I just can't see yet? I am primarily interested in starting seeds in the greenhouse in the next few weeks. Will my seedlings be at risk now that I have obvious pests in the greenhouse?

Montgomery County Maryland

3 Responses

The pest you are seeing look like aphids; both the adults (green) and the white shed skins of their earlier life stages. You should remove any infested plants.

Spending some time paying attention to sanitation will go far to help you successfully start your seeds for the upcoming season. We'd suggest vacuuming up any soil/leaf debris and wiping down all areas with a hot, soapy water and allow to dry thoroughly. You can re-use the containers, but disinfect and wipe those down too, paying attention to curled edges and under corners. We suggest starting with new soil.

As with any pest or disease, be sure to start with clean seeds and/or any seedlings or plants you may bring in. You should also regularly monitor for pests to catch them early before their populations rise. Aphids are not a big deal, but are notorious for quickly rising populations in that they have the ability to actually give live birth to females already pregnant with the next generation! They can be hand-squished or hosed off of plants as you see them.

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as usual, thanks! so I should toss all the lettuce plants? they all pretty much have pests on them and I won't go to the trouble to spray them and then I wouldn't eat them anyway. And, the white things are not a second pest, but part of the aphid problem? that's good news!

You can toss them, or just wash them off well. You can compost them, or just throw them out in the yard for birds... and yes, the white things, unless they fly when disturbed just look like shed aphid skins. If they flit around, they are white flies.