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Perennials/Brown and black spots on 2 Jasmine Madagascar plants



I've had my Jasmine Madagascar plants for almost 2 years. The stems are draped over a long trellis indoors (I have had that the same amount of time), but just recently, after I've failed multiple times in keeping my 4 mint plants alive (within the last 4 mths), my Jasmine Madagascar plants now have black, and brown spots on the stems, and now at the base of each leaf there are raised very small tiny black spots. My mint plants I believe were each time killed by either fruit flies or gnats. At one point the mint plants were covered with brown and black spots as well. I experimented with the mint plants after noticing the brown spots on the stems by placing the mint plant in a plastic bag, in the sun, a few days later, those brown spots then turned into small insects, lots of them. I'm afraid this may happen to my Jasmine Madagascar- please help.

ANSWER: Greetings, Lynn,

I am sorry to hear about your problems with such beautiful plants. I love tropicals too, but they can be a challenge because so many insect pests are attracted to them, and it is easier for them to become established indoors. You did a very good job of detective work with your mint plants, and it has guided you to an answer.

Essentially, there are two major pests of jasmine plants, but it sounds very clear that you have an attack of aphids or thrips. They function similarly. They chew plant foliage and stems and leave a residue that is often the color you describe. It happens because their nasty little jaws scrape against your plants. There are easy and nontoxic solutions, but you must be persistent.

There are chemical solutions, but let's start with the solution that has always worked for me.  And it's easy. A solution of soap  and water with a sticking agent will clog the little beasts' breathing apparatus. Have you heard of insecticidal soap? It's the first line of defense and works in a non-toxic manner on a large variety of nasties. I always keep it in stock. I just used it over the winter to wipe out a colony of whiteflies on a friend's tropical hibiscuses. I had brought them into my home and the creatures multiplied like mad.

Head out to your local garden center (perhaps call them first), and ask them for insecticidal soap. It is soap, water and a sticking agent. It is inexpensive. You can purchase it ready to use or as a concentrate. I like the concentrate. Bonide makes a good one.

See if you can find the 16 ounce concentrate. Then, if you like, get a spray bottle so that you can mix the concentrate. I believe it is one tablespoon to 32 ounces. A small spray bottle with a pump costs about $10. With your concentrate, and the bottle, you can inexpensively have the solution to many plant problems, now and in the future.

Take your entire trellis outside or to your kitchen (I have also used my bathtub!)and saturate your plant with this concentrate. Wait a couple of hours. If you can, it can be good to rinse the plant a few hours later, and then saturate it again. Do this for two or three days. Then rinse the plant, step back, and observe it. If you see any more nasties, do it again.  Once the plant recovers do keep an eye on it, in case you missed a few. The beauty of this concentrate is that it is inexpensive, non-toxic, can be repeated as often as necessary with any plant, is safe for the plant, and costs pennies per application.

I have done this with several tropicals and they are all here with me today.

Is this clear? Does it make sense? If not, please feel free to write again.

Best wishes,


---------- FOLLOW-UP ----------

QUESTION: Thank you so much Donna for your response. That day I went to Lowes and purchased Bonide Rose 3 in 1 RX, I wasnt sure which Bonide to get. I have been treating my Madagascar plants as advised, however Im not seeing much of a difference. I forgot to mention that some of the spots on the stems are also raised, while some are flat, which are the black spots. The raised areas vary in color from light brown to dark brown-it appears that these multiple spots are imbedded in the stem versus the top layer of the stem. Did I purchase the correct Bonide? If so, do you have an estimate on how long it takes to start seeing an improvement?

Thank you again for all of your help,



Hi Lynn,

Actually, I was after insecticidal soap, which was the product for which I sent you the link. The main ingredient in the product you purchased is Neem oil. Neem oil is supposedly an insecticide, fungicide and miticide. The product I wanted you to get would have simply smothered the little beasts with, was insecticidal soap, effectively soap and a sticking agent.

Unfortunately I have never used Neem oil. I found it to be a bit expensive and I was never certain that it was more effective than insecticidal soap. I like to use the simplest product, and if it works I stop there.According to the description it should work , but you as the consumer will end up being the best judge.

The directions for use are:

To control disease already  present,  apply  this  product  on  a  7  day  schedule  until  
disease  pressure  is  eliminated.  Then  continue  spraying  on  a  14  
day schedule to prevent the disease from reoccurring.

Do let me know how well it works.



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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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