Question
Hi Darlene, my question is regarding my indoor yucca plants. I have 3 of them and they were doing great when i bought them, in time it seems as though they have developed this whitish to soft,soft yellow powder like substance on them. It seems as though it appears more on the newer growth of the plant. When the plant shoots up new growth from the center of the leaves the new growth is covered in this powdery film. The coloring to the new foliage that is covered in this powder is very light green to yellow. Any of the old foliage from when it was healthy is still in great shape, very dark green and firm. They have great full sun facing west(all day sun) and i only water them when they have dried out completely. We have well water with a water softener.I bought the plants nearly a year ago and they stand about 2.5 feet tall and are in about a 10" pot(the pot i bought them in) The soil doesn't seem to have too much sand in it either. Have you ever seen this on indoor yucca's and should i think of repotting it in the same pot with more of a sandy soil mixture for better drainage. I really hope i can save these plants as they were once very beautiful and healthy.

Answer
Ginger,

It appears that your yucca may have a fungal infection that I have never seen on yucca plants before,powdery mildew . However, I have been successful at getting rid of powdery mildew on other houseplants by spraying the plant thoroughly with Lysol spray (you can use the generic brand) daily for 2 weeks. Spray the tops and bottoms of all the leaves and the surface of the soil. You need to be persistant even if it looks like the fungus is already gone.

Having 3 plants in such a small pot is part of the cause. After April 1st you need to repot the 3 plants to a 14" diameter pot and try to separate the plants so they have more air circulation between them. You need to wait till after April 1st so the daysw are longer and the plants won't go into shock.  In the meantime it may help to put a small fan on them to circulate the air while you are treating them with the Lysol spray to get rid of the powdery mildew. You can stop the treatment when the film disappears and start if it comes back. Do not leave the sit with any water in the drain tray, empty it an hour after you water them. It does not like sitting in a swamp. Good luck.

Darlene