Question
what is causing yellow blisters on a Janet Craig? the blisters are appearing on the top side of the leaf. it is not scale or any kind of insect and the spots are not sticky. I suspect a fungus. what is the best treatment? the plant is in an office environment where people working nearby may be sensitive to chemicals. I prefer to use a systemic treatment method.

Answer
Heather,

You did not say how long you have had this plant. Are they actual blisters with water in between 2 layers of plant tissue? In that case it may be a fungus and for a good systemic treatment I would reccommend you go to a good area nursery or garden center and ask what they reccommend and follow the package instructions. I have a lot of allergies and sensitivities and what I would personally use and have found effective is plain old Lysol spray. I usually use the generic form and I would spray the entire plant from at least 12 inches away making sure I got the fronts and backs of all leaves. I would spray it every 3 days for at least 2-3 weeks just befor I left for the day. That would keep the odors from bothering people too much and how many will complain about Lysol?

That said, I think your problem may not be a fungal problem. If it is not an actual blister but just a yellow cirle on the surface of the plant leaf it is another problem. Are you watering your plant with city water that has chlorine & flouride in it? If so all Dracaenas (a Janet Craig is a variety of Dracaena) hate water with chlorine and flouride. It causes yellow circles on the leaves that eventually dry out to even make holes in the leaves. You can start watering with distilled water or you can allow the tap water to sit in an open bucket for 48 hours prior to watering your plant so the chlorine and flouride dissipates into the air before you use it. Then it will not harm the plant. If you have more questions feel free to write again. Good luck.

Darlene