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Perennials/My Phlox are failing


Hi, I'm located in upstate New York . My phlox are not looking good. The bottom leaves are withering and brown, the upper leaves are getting yellow areas. I had this last year .. After 15 years of trouble free and gorgeous phlox. I have a lot of phlox, they are the backbone of my garden. This spring I divided most  and cleared out almost 1/2 the plants hoping that would be the answer...but no.
What have I got going on here? Blight? mites? Blight and mites?
And most importantly, How do I stop it?

Hello Sue,

Withering and brown..hum. My candidates are aphids or spider mites. Both turn the leaves of phlox yellow and brown. Aphids multiply like crazy. They are basically able to reproduce without a mate, so you can go from having two to literally thousands. But, happily, they are easy to control.

If the leaves are also curling, you may have spider mites, which multiply in hot, dry weather.  Spider mites are more persistent, and you may have to treat your plants for a couple of weeks. You will know that you have them if you see tiny webs on your flowers.

Happily, both sets of creatures succumb to the same treatment- a sharp spray of water or insecticidal soap.There are two good ways to do it, and both are organic. The good thing about the aphids is that once knocked off plants they can't get up, and the birds come in and get them from the ground. If you have a garden hose with a spray arm, all you have to do is use the sharp spray setting, blast your plants, top and bottom (make sure that you get the underside of the leaves). Do this for several days in a row. Try not to skip a day, because if you do, like the Terminator - they'll be back!

The other alternative is to use insecticidal soap, which you can find in any garden center and many hardware stores. Buy the concentrate, dilute it in a spray bottle, and spray your plants, again, top and bottom, making sure to get the underside of the leaves, because they will hide there.

Lastly, if you are giving your plants a lot of fertilizer, hold back. Lush growth is a magnet for aphids. They love it. I used to overwinter a rose in my garage, so it was the first thing to break dormancy - long before outside plants. I would take it out of the garage to find it covered with hundreds of aphids, feeding away because nothing else was green. I would pull out my spray hose, give the plant a sharp spray for three days, and no more aphids.

Spider mites like heat and dryness.

Your act of clearing out about half your plants was an excellent strategy on your part, since crowded phlox tends to suffer from fungal diseases, and I believe you have prevented those.

Is this clear and helpful? If you have any other questions please do not hesitate to contact me.

Best wishes,



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Donna Mack


I am a Master Gardener through the University of Illinois Extension.I can answer questions about pest control, especially voles, rabbits, chipmunks and slugs, and have done so on Dave's Garden Watchdog under the name DonnaMack since 2002. I have a lot of expertise with ornamental grasses, hardy roses and old garden roses, minor bulbs such as ornigothalem, chionodoxa and allium as well as most types of lilies. I lived in a conservaton community and have great familiarity with native plants. I am knowledgeable about organic methods and I grow perennials, annuals and vegetables from seed.


I have been gardening since 1998 and have raised roses, peonies, annuals and perennials (the latter two from seed), and numerous shrubs and trees, many of which I have planted. I am familiar with many organic techniques and use as many as I can but know the chemical solutions, which are most benign and how to use them. I LOVE gardening, and I get great satisfaction with helping others so that they reach the state of joy that gardening can bring to those inclined to it.

The American Lily Society and the Wisconsin Illinois Lily Society

I have numerous entries in Garden Watchdog under the name DonnaMack. I write three to four columns a year for the Kane County Chronicle. I also write articles for Daves Garden Watchdog.

I successfully completed the University of Illinois Master Gardening Program in March of 2013 and have maintained my certification every year since. I did this to augment extensive self study through books (I've probably read 100) and an arts degree, which helps with aesthetics. I am purely an amateur, but one who studies, reads, and documents extensively. My gardening log began in 2000, and has hundreds of entries, so that I can use my successes and failures to assist other gardeners.

Awards and Honors
The University of Illinois created a Team with Work Award for master gardeners who work together to create what they regard as an outstanding project. I won this award as part of a group that created "The Idea Garden", which suggests plants for home growers to attempt to grow. My personal contribution was salvias - ornamental and culinary hardy and tender perennials, which I grew from seed and tended through the season. I have recently been asked to join the Speakers Bureau, which would require me to present topics to various groups under the auspices of the Master Gardening program.

Past/Present Clients
I am currently overseeing and performing the maintenance of ten gardens in a suburbs of Chicago.

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