If you have adopted container gardening and your plant doesn't look very well, a pest or disease might be the culprit. Here is what to do to contain the damage and prevent this kind of situation.
Identify the root cause
Should a problem arise, take the time to properly identify the cause: poor growing practice, pest, disease, too much sun, frost, and so on. In many cases, a plant is in bad shape due to inappropriate growing conditions. For example, are you watering your plant adequately? Does your container have drainage holes?
A plant subjected to poor growing techniques is more vulnerable to pests and diseases.
Apply the right control method
If the source of the problem is a pest or disease and an intervention is necessary, choose the control method that has the least impact on human health and the environment (manual collection of insects, pruning of infested parts, water jet to remove pests, etc.)
Pesticides, even those considered to be low-toxicity (like insecticidal soap), should only be used as a last resort, as they can affect the beneficial organisms such as ladybirds. Comply with your municipality's pesticide regulations at all times.
Prevent pests and diseases
To prevent pest problems and diseases, pick healthy plants well suited to the conditions in which they’ll be growing and not subject to insect attacks and pathogens. Maintain them appropriately and inspect them on a regular basis.