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Perennials/pentas pests


I live in Fl. and have several pentas plants.  I have one that has a lot of white stuff on it.  I have enclosed a picture.  Will it harm my plant and if so, how so I control it?

Hello Mary,

Please forgive me for taking so long to answer your question. I was out today.

Pentas are lovely plants with few problems. One problem, however, can be powdery mildew, which is caused by a common fungus, particularly under humid conditions. It can weaken a plant, but from viewing the pictures I can see that your powdery mildew is in the early stages, when it is easiest to treat and control.

Please begin treatment by removing any affected leaves. If you use pruning shears or snippers to perform this removal, do remember to disinfect them by using rubbing alcohol or dipping them into a solution of one part bleach to nine parts water between cuts. You perform this step to avoid passing the fungus from plant to plant. Next, utilize elemental sulphur, a safe to use, non-toxic and organic remedy used for several fungus diseases (black spot is another). Elemental sulphur is inexpensive. Good, widely available brands are made by Safer and Bonide. You will find them in any garden center and they are commonly found in hardware stores. They are also widely available on the internet. You can purchase it ready to use, or you can purchase a concentrate (which I do), get an inexpensive spray bottle (which you can find in the same locations) and spray your plants (wait until the temperature is under 80 degrees) every few days. Temperatures over 80 degrees will cause the plants to become burned.

Other steps that you can take include avoiding overhead watering that causes the leaves to become wet and provide a good breeding ground for fungus. Lastly, it would helpful if you place the plants in an area of good air circulation. Stagnant air is the friend of fungus.

Is this clear?   Please feel free to write again if this is in any way unclear or you need more information. I am happy to help.

Happy New Year Mary!

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 grass, hardy roses and old garden roses, minor bulbs such as ornigothalem, chionodoxa and allium as well as most types of lilies. 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

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 successfully completed the University of Illinois Master Gardening Program in March of 2013. 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.

Past/Present Clients
I am currently overseeing and performing the maintenance of two large English style gardens in a suburb of Chicago, and recently acquired the management and redesign of a large estate garden(2015.)

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