Houseplant Leaves

Question: Can you help me figure out what’s going on with a houseplant? I think it’s a dracaena. 

Attached are photos of the plant, which looks healthy, and of 3 leaves I cut off yesterday which do not! The brown spots do not appear to be moving - not alive? Some can be wiped off but most cannot be. The leaves are covered with a sticky substance. 

Thank you very much for any help you can give me.

responder: An Ask Extension Expert Replied July 13, 2023, 2:27 AM EDT
response: Hi Katherine - My little app thinks your plant is a spineless yucca, but whether it is a dracaena or a yucca, you have some sucking insects on it.  These insects create the honeydew you are experiencing.  The brown spots are where they have damaged the tissue of the leaf.  You said that some can be wiped off.  I will take a guess that you have some type of scale insect, or spider mites on your plant.  Are just the older leaves effected?  Or do new ones show damage, too?  It is natural for older leaves to turn yellow and eventually fall off.  However, newer leaves should not have spots like the photo on the right.  Check under the new leaves and see if they have any stickiness or honeydew.  If you take a white paper towel and quickly pull it across the leaves, do you get any red coloration?   Mites are treated differently than Scale insects, so try that test and let me know what you find.

responder: The Question Asker Replied July 13, 2023, 9:44 AM EDT
response: Hi Denise, 
Thanks for the quick reply! 

Here’s a photo of what I got when I did your test. The spots look brown to my eye but are red in the photo.  I tested lower leaves that had sticky stuff. Upper leaves are not affected. 

How should I treat this plant? It is not near any others but I do have another one in a different room - so far no signs of infection there. 

How did this plant get infected? I have a lot of houseplants. What do I need to do to keep from spreading the infection?

You’re right, it’s yucca. 

Thank you very much for your help!
Kate



Sent from my iPhone

responder: The Question Asker Replied July 13, 2023, 2:57 PM EDT
response: PS I noticed some suspicious spots on a wooden carving that was next to the plant. What's the best way to disinfect that wooden statue? Thank you!On Thu, Jul 13, 2023 at 9:42 AM Katharine B. Soper <<personal data hidden>> wrote:Hi Denise,  Thanks for the quick reply!   Here’s a photo of what I got when I did your test. The spots look brown to my eye but are red in the photo.  I tested lower leaves that had sticky stuff. Upper leaves are not affected.   How should I treat this plant? It is not near any others but I do have another one in a different room - so far no signs of infection there.   How did this plant get infected? I have a lot of houseplants. What do I need to do to keep from spreading the infection?  You’re right, it’s yucca.   Thank you very much for your help! Kate    Sent from my iPhone

responder: An Ask Extension Expert Replied July 13, 2023, 6:13 PM EDT
response: Hi Kate!  I grow orchids and have a lot of experience trying to kill the two types of scale typically found on orchids.  Since you have only one plant with this problem, I would not recommend an expensive solution.  At Big Box stores, they have a ready-mixed product that is effective called “Insect and Mite Control”, which kills aphids, mites, fungus gnats and crawler-stage (baby) scale insects as well as others.  I recommend this spray for houseplants ONLY (not on anything edible!)  The adult scale, which can be difficult to kill since they create a shell type casing over themselves.  I recommend Neem Oil for the adults.  Neem oil covers the adults and does a fair job of smothering them.  Keep watch on this plant and be sure your problem doesn’t start up again.  Spray it all over so it doesn’t spread.  Keep out of direct sun after  spraying with Neem, because the sun can burn the leaves.  Neem is a safe natural product.  I also use it on Rose Bushes for aphids, and it is very effective against them.  Get ready, Neem smells like rotten peanut butter.  LOL.     Sometimes, you have pest A, and it is spread by pest B.  I’ve seen ants very happily farming scale and lapping up the honeydew the scale create.  It could be your pests are collecting hitchhiking scale crawlers.  I recommend taking plants outdoors in summer.  Some natural predators take on some of these insect pests.   But of course, you introduce another group of pests when you bring them inside.  One thing, if you have your plants inside during summer, they might lack enough humidity to keep the spider mites at bay.  Mites are more prevalent in a dry warm environment.   I hope this helps.   If you continue to have problems, write again, please.