Hello,

What I can see in your pictures(thank you!) are some aphids, and many skins shed by aphids. I think this is what you referred to as sawdust. Aphids reproduce so quickly that they can 'out run' the good, predatory insects.

The natural predator insects, like lady beetles, help control them. Insecticidal soap kills them. 

Here is a reference that lists chemical control options, too. 

http://www.clemson.edu/extension/hgic/pests/plant_pests/flowers/hgic2102.html

Some of the leaves are so brown that there may have been another problem, too. So check your plants still green leaves and compare the start of any more symptoms to the listed pests/diseases in the article, above.  If you need more help after you have controlled the aphids, please write us again.