Spider mites can be a plague. Once one plant gets spider mites, they can infest all of your container plants pretty quickly. Unfortunately, it's very hard to get rid of spider mites. Sometimes, you just have to pitch the plants that get them. Be careful, if you have to get rid of plants that are infested, and do not compost them. Sadly, the best way to get rid of them is to put them in plastic bags and put them in the garbage.
Identifying a Spider Mite Infestation
Spider mites are tiny—smaller than the head of a pin—so it's hard to see them. To identify an infestation, you can check to see if there is webbing on your plants, particularly at the intersection of branches. Another sign of spider mite infestation are leaves that are spotted or speckled. Spider mites can range in color from red to light brown, yellow, or green.
Steps to Battle Spider Mites
Like most plant pests, you have a much better chance of dealing with spider mites before you have an all-out infestation. The more mites, the more eggs, and the harder it is to control them. The first line of defense with almost any insect problem is to spray the plants with a hose, trying to knock as many insects off as possible. Make sure to spray the underside of the leaves as well as the tops.
Once the plant is dry, try an insecticidal soap spray. With large plants, it's hard to get good coverage all over the entire plant, including the undersides of leaves, but do the best you can. Insecticidal soap is preferred over a pesticide because it doesn't harm beneficial insects and is listed as acceptable for organic gardening.
After insecticidal soap, try neem oil or a neem oil combination. A disadvantage of neem oil is some people don't like the smell and it can be sticky if it gets on walls and furniture.
Chances are you will have to keep spraying your spider mite-infested plant every seven to 10 days in order to interrupt the cycle of eggs hatching. Also, make sure to spray the soil as well as the entire plant.
There is no absolute answer as to when to dispose of the plant unless it is completely dead. Even then, plants can surprise you and bounce back. You can battle spider mites over the winter and cut back the plants severely in the spring, then put them outside. Some of these plants rebound, thriving throughout the summer. However, on bringing them back inside, the mites can return with a vengeance.
How to Prevent Spider Mites
Prevention is always the preferred option when it comes to mites. Before you buy a plant, look for the telltale signs of spotted leaves or webbing. If you see any indication of mites, don't buy the plant or any plants nearby. Also, mites like dry and dusty conditions, so keep your plants hydrated, with a good amount of humidity in the air. These conditions will be inhospitable to mites.