Answer: Fine webs on leaves and stems are usually caused by spider mites, this could also cause spots on the leaves. They could also be suffering from aphids, soft bodied sucking insects.Insects feeding on the foliage can also lead to a type of mold growing on the sugary plant juices. Since you are in such a contained space you might consider throwing the plants out if they are badly infested or if they do not respond to treatment. You can treat both aphids and spider mites with insectidical soap, being careful to apply and reapply according to the label instructions. Spider mites often attack plants in a hot dry location, so increasing the humidity level would help slow them down. Aphids tend to attack overly succulent new growth, so make sure you are not over supplying them with nitrogen.
Q&A Library Searching Tips