The good news is that there are only about six or so species of aphids common to greenhouses. By looking, with good magnification and lighting, from a top rear view, at the notch on their head between the antennae called the tubercles, you can differentiate these four species (see the chart on page 24 for the identifying characteristics and notes on biology).
If you can’t identify the aphid, it is recommended that you reach out to your local Extension agent or another person knowledgeable in insect identification. Bring in a bagged branch with live aphids, or put multiple specimens of the aphids in a container with 70% isopropyl alcohol when submitting a sample.
Fortunately, many predators and parasites like to feed on aphids, and successful biocontrol is possible. Biorational products such as the entomopathogen Beauveria bassiana and the natural insect growth regulator azadirachtin, as well as soaps and oils, can all be used, along with good scouting, into a highly effective integrated pest management program. But, first, you must ‘Know thy aphid’!