Greenfly and how to get rid of them
Aphids in general, blackfly, green fly are possibly the most widespread plant pest problem in the garden. They attack a wide range of garden and indoor plants from annuals, perennials and vegetables to trees, shrubs, climbers, roses and fruit. Gardeners with aphid problems need to take steps to control them before it's too late.
Some species are specific to a plant or group of plants, and some produce characteristic damage to the plant but luckily, green fly and other aphids have many natural enemies - including ladybirds, hoverfly larvae, lacewing larvae and several parasitic wasps. If your garden is short of these, you can now buy them from biological control suppliers.
One excellent way of getting rid of greenfly without damaging your host plants is to fill your sprayer 1/3 full with distilled white vinegar and top up with 2/3 water. Give the solution a shake and then give your aphids a good spray. This will kill them on contact so you then need to carefully spray them off your plants with the garden hose. This method is both cheap and eco friendly.
Another method of control is to keep a regular/daily in summer eye on susceptible plants and squash the one or two aphids you see before they build up into huge colonies. In this instance we use a small hand pump water sprayer - nothing too powerful or you may damage the plant, but we find that rinsing them off at the same time as squashing them with your fingers works a treat.
There are some chemical pesticides that you can use on all aphids, blackfly and green fly alike. Those sold as 'organic' are contact insecticides, which means you have to hit the aphid to kill it - miss even one and it will soon develop into a colony of thousands very quickly. This means you need to check plants regularly, and daily in the summer.
Systemic insecticides, containing thiacloprid or acetamiprid, provide the best control; they also kill on contact, but are also taken inside the plant where they go on to protect against further attack for several weeks.