I found a few uninvited guests in my greenhouse this week.
I know these little pests as greenfly, but they are otherwise known as aphids, blackfly or whitefly.
I usually control greenfly by spraying the infected plants with a heavily diluted soapy water mix.
Other methods of destroying greenfly include the introduction of natural predators such as Lacewing (Neuroptera) or Ladybirds (Coccinellidae).
Please let us know what methods you use.