Aphid control means 1) understanding what this pest looks like so you’re 2) using the right technique to control the problem.
These guys also come in black, very pale green that appears almost while and I’ve even seen the odd pinkish one. You’ll mostly find aphids on the growing tips of plants or under the leaves.
Aphids with the predator LadyBug Beetle
Identifying the Problem
Aphidsuse a sucking mouthpart to pierce the leaf and suck the juices from it. In severe infestations, the sap running from the leaf will be attacked by fungus and (mixed with the nutrients from aphid excreta) will turn black. It will resemble a black streaking or soot on the leaves.
And it is sticky should you care to put your finger on it to check. Leaves or growing tips of plants will also be stunted or curled as the growing points were damaged by feeding.
The nice thing about aphids is they are considered “food” by a large number of good garden insects (such as the ladybug shown here with the aphids). You’ll that most of the pests are eaten before they become a problem.
Simple Control System
Aphid control is as simple as knocking them off garden plants by using a strong jet of water. This jet knocks them off the plant to the ground where beetles and other predators make short work of them. They will not survive to recolonize your plant.
If You Have to Spray
If you really want to spray something, Insecticidal Soap will kill them, as will Neem. I note Rotenone dust (note this can be harmful to humans and you should wear a mask when using!) and Diatomaceous Earth are also labelled for this pest in many areas.
If there’s only a few, such as on the growing tips of roses, then a quick swipe of the hand will crush them (it’s a bit gross but it works effectively). But the easiest, quickest, cleanest and safest is a strong jet of water.
And no, using water in this way once or twice a season is not going to increase the incidence of molds or fungal problems.
Aim Spray Properly
Remember that you have to get any kind of spray or dust (be it a strong water jet that does it naturally or a nozzle pointed upwards) under the leaves to kill the bulk of the population that are hiding from sight.
Aphid control is one of the easiest techniques in the organic gardening world; this is a good thing because aphids are the most numerous pest.