Rue with white dots and some 3mm white bugs

Question

I have a Rue plant in my terrace, and for many weeks it has had some sort of plague made of white dots and some slightly bigger bugs, oval shape, no more than 3mm long.

I've been using an organic repellent, with very little success.

I don't even know the name of this plague, so I've posted it here if anyone knows it or has already dealt with it in the past.

Here are some photos of it:

What I know about its "behavior": it prefers both sides of the leaf, and the bigger bugs (those oval shaped) reside on the nodes of the stem, preferably into the most tight part of it (the third picture shows it).

Answer 1

This is most likely to be a scale insect but we can do a little diagnosis tree:

• do they fly if disturbed? => aphids or thrip
• do they look like they are surrounded by a cottony tuft? => mealybug
• are they hard shelled and need to be removed with your finger nail or a toothbrush? => scale

There are many different types of scales but the ones in your picture look similar to these ones or these ones.

Control measures are similar for aphids, mealybug and scale. Mix about 5 ml of dish soap to one litre of water. Scrub the rue with a soft toothbrush or cloth then rinse with water. Repeat at five to seven day intervals at least twice.

If the problem returns consider cutting back the plant hard and reapplying soap and water. The plant will regrow and the less area you have to control the easier it is.