Hi dude, green flies might be some aphids. ecover zero is indeed "eco friendly" but I wouldn't be fast in using it for the plant...there's other methods. One thing to have in mind would be...how are the insects affecting your plan? any spots, leaf bites?
Get yourself some diatomacious earth; you can put it on top of the soil and will prevent anything from getting near your plant's roots and make a light mix with water and spray it on the foliage and this will protect it from any insects. Also neem oil has good properties. Also if you grow outside, would be great to consider some plants that will help you and your plant. Things like clover (increases the nutrients in the soil) and camomile (good against insects and fragrant plan to mask other smells), etc
Best of luck