By Benpcoleman
California,
United States 
Help! Need ID of possible disease? Can't keep this brugsmania healthy (started from seed) and looks like dahlia next to it is infected. We are in coastal southern ca. Thanks!
3 Jul, 2015
Answers
Thrips would be my suggestion for the Dahlia with possibly Red spider mite for the Brug. Brugmanias hate being starved, dried out too much or pot bound....if any of these happens, they can get stressed and allow pets such as RSM to infest.
3 Jul, 2015
I agree with the red spider mite but I believe that it is only Provado Ultimate Bug Killer2 - Aerosol that will deal with it. I have found that the ordinary concentrate will not.
4 Jul, 2015
The Dahlia looks like it has spider-mite, a pest of hot and dry conditions. It could also be an aphid or a thrip, all can leave the white spots but my guess is spider mite.
Misting the plants can help, spraying is not recommended as spider mites become immune to pesticides very quickly. Predators can be purchased to control them.
3 Jul, 2015