Question
I noticed my banana and hawaiian plants that I am housing indoors
for the winter are loaded with spider mites I will attempt the
spray method you have recommended however my banana plants are down to new a growth leave only. The rest of the leaves are either dried up or 50% dead. I really want to try to save them. Would I need to rid the current soil the plants are in? Do spider mites also get into soil? Is spraying the soil with the soap mixture also effective as well. If I do not want to change the soil if it is not necessary.
Thanks, Debbie

Answer
Hi Debra,
   I have some good news for you and some bad news. The bad news is since your banana plant has lost so many of it's leaves, there is a chance that it may not recover from both the leaf loss and the damage caused by the spider mites. However, the new growth is a good sign so hopefully once the spider mites are gone the plant will recover nicely. Put the banana plant in a place where it will get plenty of bright light but no direct sunlight. Be careful not to overwater it. Allow at least the top 2 inches of soil to dry between watering. While the banana plant is actively growing, you should fertilize it very lightly and often. I recommend using any well balanced liquid fertilizer and diluting it with distilled water. I usually dilute fertilizer 50% fertilizer to 50% distilled water. As long as the plant is producing a good amount of new growth, fertilize it every other time you water it. Banana plants like lots of humidity. You can raise the humidity around the plant by either placing it on a tray of pebbles filled about halfway with water or by grouping it together with other plants (after you are sure the spider mites are gone of course. Don't want the spider mites spreading to other plants). You can also try misting the plant regularly.

Okay, the good news now. Spider mites do not get into the soil so you do not need to change the soil or repot the plants. Putting soapy water into the soil a plant is in is never a good way to deal with insects in the soil. The soapy water could kill the plant as well as any insects that may be in the soil.
When you treat a plant with soapy water, either by spraying it on the plant or by dipping the plant in soapy water, there is always a small amount of soapy water that gets into the soil no matter how careful you are. So far I have never had a problem with just a very small amount of soapy water getting into the soil. If more than just a tiny bit of soapy water gets in the soil then you will need to 'flush' the soil. To flush the soil, water the plant with distilled water until a good amount of water drains out the drainage holes in the bottom of the pot. After a few minutes, when the water has stopped draining out of the bottom of the pot, fill it up with distilled water again and allow it to drain. I usually 'flush' (fill and drain) the pot 3 times. After an hour or so be sure to check the drainage tray under the pot and empty it if there is any water in it. Never allow a plant to sit in water. If there is any water in the drainage tray the soil will soak it up through the drainage holes and keep the soil too wet, which could cause root rot.

Don't forget to spray the leaves, especially the undersides, with a strong spray of water to wash off as many of the spider mites (and eggs) as possible before you treat the plants with soapy water. This is a very important step in effectively treating the plants for spider mites.

Also, remember to rinse off the plants thoroughly after spraying them with the soapy water.

I hope this helps. If you have any questions or need additional information please don't hesitate to ask.
     Thanks
       Tracy