I have an umbrella tree that is over 30 years old. I put it outside in the summer and bring it back in the fall. In the winter it is sitting by a south facing window. The new leaves on top of the plant are fine, but the old leaves are turning yellow and streaked. Is it a bug? What can I do about it.
Let me explain why I do not recommend moving houseplants outside in warm weather. Outdoor light is much more intense for plants than indoor sunlight. When new leaves emerge, they are adapted to the light they receive in that location. When the plant is subsequently relocated, many of the older leaves are no longer acclimated to the new light intensity. As a result, they discolor and slowly die. New leaves that emerge are adapted to the new light level and will be fine until they are moved to a different light intensity.
The solution is to find a good location indoors for your houseplants and keep them there year round. If you have to move your plants outside in summer, then be sure to keep them in shaded locations outside and in sunny locations indoors. That will help even out the differences in light intensity.