| I have two sick Monarda. The 'Snow Queen' is suffering from whatever bothered it last year; the leaves get yellow,start to wilt, then splotchy purple/black, the stem turns black at the base and then it all turns black & dies. It never got around to blooming, but came up nicely this spring despite it all.
This year it is at it again, as is the 'Marshall's Delight' planted nearby, which is blooming despite various stems dying. I've noticed that the base of the stems are covered with ants (who seem to be chewing the stem) and the plants seems like it isn't planted deeply enough---the stems are growing almost on the surface, then bending up and away.
They get plenty of sun and lots of air, and have had plenty of rain (that's an understatement!)To think I planted them because they would be easy!
|Monarda is often attacked by mildew, but in my experience the symptoms of that infection primarily affect the foliage rather than the stems as you described so I do not think that is the problem based on your description. (It can be controlled with applications of horticultural oil every two to three weeks according to the label instructions. ) It is possible that you are describing "yellows" a particularly nasty problem in that it is not easily treatable. Here is an illustrated description of that http://www.agric.gov.ab.ca/agd... for you to compare with your plants.|