Question
one by one our myrtle topiaries are developing a white fungus on the interior plant stems. it begins with killing the leaves, then finally the entire plant.  it also will move from plant to plant.  what is it
and how do I treat it?  they are watered weekly while indoors for the winter.  

thank you, bill

Answer
Hi Bill,

Your description is not very specific, so it is hard to be sure. However, your Myrtle probably has an infestation of mealybugs, which are often described as looking like a fungus. Mealybugs look like tiny bits of soft cotton. The only other possibility is a spider mite infestation that would cover the leaves with tiny webs.

In general, myrtle topiaries do not thrive indoors in winter because they prefer lots of fresh air and sunlight. Because they are under stress when indoors, they are more susceptible to pest infestations.

Mix a solution of 5 parts water, 1 part isopropyl (rubbing) alcohol and a squirt of liquid soap. Then, thoroughly spray the entire plant so that all leaf and stem surfaces are dripping wet. This thorough, but messy, spraying is essential so that there is direct contact with all of the mealybugs, including the juveniles that are nearly invisible. If you miss a few they will reproduce and the infestation will return a few months from now. If you are really thorough, one treatment should be adequate.

For the winter months, try to give your Myrtle as much direct sunlight as possible and allow the soil to dry deeper into the pot than you do during the outdoor summer months. Water them based on need rather than by the calendar.

I have written an article on treating plant pests that I will email for free to you (or anyone else) who sends a request to me at [email protected].

Please let me know if any of this is unclear or if you have any additional questions.

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Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

Visit my website at: A link to PlantCareExperts.com