if you see any ladybugs hanging around the windows (they sometimes do around this time of year) that might help, otherwise I'm not sure what you could do other than to smash them when you see them. I've got a ton of baby praying mantids in case anything attacks my seedlings...

"Are they too young to be sprayed with anything else?"

No, they are not too young to be sprayed with an insecticide. There are both organic source and synthetic source insecticides available to spray for aphids on young (greenhouse/nursery sized) tomato plants, even young sprouts.

Select an applicable/appropriate product by reading the label to discover the target bugs and specific use (safe for use on edible vegetables, tomato plants, etc.) and just follow the label directions explicitly when handling, mixing and applying an insecticide ... whether organic or synthetic sourced.

Insecticidal soap may work okay. It is a little early to be spraying them with anything - tender little things. I don't remember having ever sprayed tomato seedlings quite as young as yours.

I haven't had good luck with aphids and rotenone/pyrethrum.

Insecticidal soap doesn't work very well in the greenhouse, from my experience. Since the bugs have to dry out to die . . . maybe, the high humidity in the greenhouse lowers the effectiveness.

If we can every get a warm, still day in this neck of the woods, putting plants outdoors in the shade and spraying them with the soap may be a good way for you to get past the problem. I have done that often. You probably have quite dry air indoors and taking them outside might not be necessary .

No sun! You may also rinse them with a clear water spray after a couple of hours.

Now, it would be good to know if anyone has used insecticide on such tiny seedlings.

Steve

Well, while I was typing, Hoosiercherokee was commenting.

I realize he has significant experience in tomato growing. CMK, I'd go with what he has to say.

Steve

I'd also be looking for the source of them. Rare inside the greenhouse unless brought in on something and even more rare inside the house unless you bring in an infested house plant.

Also what is attracting them? Lots of nitrogen fertilizer?

But if they can be sprayed with anything they can also be lightly sprayed with water - like the sprayer on the kitchen sink. You can also clean them off with the sticky side of masking tape. Just take a popsickle stick or similar, wrap the tape around it backwards and lift them off.

Dave

Some great ideas here, thanks so much!

-hoosiercherokee, so insecticide (natural or chemical) will not burn them at so young a stage?

-Dave, they hitchhiked indoors on a couple of annuals I overwintered. They have infested my shamrock, and no amount of sink spraying seems to work on them! Guess I will have to buy a product for the houseplants as well.

One thing I found interesting...certain tomato seedings seem more attractive to them than others. Great White is the favorite snack so far...
CMK

I have an aphid problem indoors every year in my seed starting setup. The only thing I can figure is that using the rainwater in my rain barrels must have aphid eggs in it. The buggers get inside and go after the eggplant and pepper seedlings. They hang around on the tomato plants, but don't do any damage to them. I am trying to organic mix of baby oil, garlic juice and Dawn dish soap and then mixed with water in a sprayer. It seems effective for like a day and then they come back, so I spray them about daily. The eggplant leaves are miniature 'maimed', so I dunno what is worse.. aphids have a chew down or funky weird looking plants.

I used a combo of Neem Oil/Safer Soap last year. Put it in a pump-up yard sprayer and every time I would spot one, sprayed every seedling. In less than a week, they were gone.

Mike