Posted: 16/04/2014 at 13:33
To be honest Flower, i would bin those, cosmos grow so quickly this time of year, they will be up and away in a week, and so much stronger, you can then plant out on May. if yours are flowering now, they will be over before summer had started.
I sowed some last year in June, on Monty Dons advise and they flowered through till oct/ nov time. Its not worth messing about with infested seedlings.
Dont let them flower until you have a big plant, pick any buds off as they will sap the strength of the plant until its bigger.