Question
Hi...We purchased an indoor yucca plant from nursery that had a few small black round spots on lower leaves....the spots are progressing upward on plant and the bottom leave yellows and shrivels and then I cut it off....how can I eliminate these black spots?  Thank you, Kay

Answer
Kay,

It would be helpful if you sent me a picture of these spots. They could be fungal or bacterial spots caused by fungus or bacteria in combination with too much water. This plant needs to be dry for at least 4 days between waterings. That means you water it then wait till it seems to be dry then wait 4 more days and water it again. To get rid of the fungus or bacteria you spray the entire plant lightly making sure you get the fronts and backs of all leaves and the surface of the soil every 3 days for a month. That will kill any fungus or bacteria infecting the plant.

The black spots could also be an insect called scale. If you can take a knife and flick the black spot off the plant into a paper towel it is an insect and you need to get them all off the plant ASAP. You can do that with Q-tips dipped in rubbing alcohol in a cup it will kill them on contact and you can rinse the Q-tip in the cup of alcohol and keep going. When you are done with the visible ones there will still be invisible tiny immature ones. To kill them before they settle on the plant and start laying more eggs you need to spray the entire plant lightly making sure you get the fronts and backs of all leaves and the surface of the soil every 3 days for a month with a mix of 1 pint of water mixed with 1 quart of rubbing alcohol and a teaspoon or dish detergent. You have to do it for 30 days because scale can hatch out for 3 weeks from the insects you are killing originally.

Those are the 2 possible causes of your black spots. Figure out which problem you have and follow the instructions consistently to resolve your problem and save your plant. Also be very careful not to over water this plant. In the winter when the days are shorter it needs even less water. Watering once a month is enough. Good luck!

Darlene