Two months ago my house plants were attacked by aphids or some similar bug. I sprayed them heavily and religiously with Safer’s Soap, four treatments in 28 days. Now some plants have dead leaves and others have leaves with these huge discolourations which seem to start at the tips and travel back to the stems.
What’s wrong and how can I restore my plants to a healthy state?
Identifying problems in “house plants” can be difficult. Even though the term “house plants” can be applied to many types of plants, the problems that can affect them are relatively limited. Common insects that affect most houseplants are aphids, spider mites, mealy bugs, scale, thrips and whitefly. Plants grown indoors can be susceptible to several diseases if cultural conditions (light, humidity, air circulation and water) are not appropriate for the particular plant. Furthermore, there are abiotic problems that are caused by a combination of environmental and physiological factors such as over-watering, incorrect lighting and overuse of pesticides or fertilizers. When trying to diagnose a problem, one needs to consider many things in order to provide the appropriate course of action to restore plants to good health.
You mention “aphids or some similar bug” and that you “sprayed them heavily and religiously with Safer’s Soap….”. While aphids may have been a problem, it’s important to try to identify the insects before treating. An excellent web-site for identifying insect problems is: https://www.extension.umn.edu/garden/insects/find/houseplant-insect-control/. Safer’s Soap can be useful in treating aphids, scale, spider mites and thrips. However, your heavy and religious treatment may have contributed to the problem of dead and discoloured leaves on your plant–too much can cause leaf burn over a period of time.
There are other factors that may also be contributing to the problem. The change in the amount of light that your plant is getting may also be causing the leaves to discolour and die. Is the plant getting more direct sun (if near a window, the angle of the sun lowers as the season changes)? Is the plant getting more or less water? Finally, a drop in temperature near your plant may also cause the leaves to discolour and drop; rubber plants tend to be susceptible to changes in temperature. Nevertheless, it is normal for plants grown indoors to occasionally drop leaves and become a bit stressed due to seasonal changes–the amount of light, temperature & humidity changes (heating during the winter), etc. If you check your plants on a regular basis, you’ll be able to prevent problems with your plant.
In order to restore your plants to a healthy state, you will need to first determine what might have caused the initial attack of pests. Healthy plants generally do not attract pests; however, there are many things to consider; please see: https://extension.psu.edu/plants/gardening/fact-sheets/houseplants/houseplant-problems.
Thank you for contacting the Toronto Master Gardeners; we trust that with this information, your plants will survive for many years.