Generally, Snake plants (Mother in law’s tongue) are not very susceptible to pests. These are robust plants with the ability to survive harsh weathers and infrequent watering. However, in favorable conditions to grow, insects and fungus can infest the Sansevierias. Warmer and dry air may encourage the spread of pests and diseases.
If you find your snake plant getting sick, identifying the exact cause is surely the first step. To determine the underlying cause, you must look for the key symptoms that the plant is showing. This will ultimately help to know how to tackle the problem. Read along to learn about different kinds of pests your Sansevieria might have, how to identify, treat as well as prevent such issues in future.
The most common illnesses for snake plants are caused by insects. The major pests of Sansevieria species include moths (worms), spider mites, mealy bugs and thrips. Moths, thrips and male mealy bugs have the ability to fly, while spider mites are so small they can float on a strong breeze. In this way, they can easily infest nearby plants or invade most part of a greenhouse.
Many houseplants, including mother in law’s tongue are susceptible to mealybugs. These bugs can be identified by their flat appearance and waxy layer they leave behind. They can lay 50 to 100 small eggs in the same waxy layer. Mealy bugs are oval in shape and have whitish segmented soft bodies.
Mealybug females feed on the sap of the snake plant. While feeding, they create small visible wounds on the leaves. This can harm the water storing cells in the leaves, eventually making them store less water. Mealybugs will make the leaves weaker by sucking on their juice. In the advanced stages, this can even make the leaves fall off.
- If you identify mealybugs on a small, localized scale, handpicking and dabbing them in alcohol is an effective method. You can manually pick them off the plant and kill them using alcohol.
- Another option is to use a cloth or paper towel dipped in alcohol and wipe them off the leaves. You can also use cotton swabs with rubbing alcohol.
- In an extreme case, you can force the bugs out using water spray. Take your plant outside, remove it from the pot and hold it upside down. Now spray the leaves with a relatively strong stream of water. It might take multiple applications to remove all the bugs. After this, let the plant hang upside-down overnight to drain all the water. Don’t place the snake plants in strong direct sunlight. Later repot it in a fresh soil.
- If the mealybugs have already laid eggs in crevices of the plant, you may not get rid of them with water. Synthetic insecticides work best in this case.
Spider Mites (Tetranychidae)
The snake plants are prone to spider mites as well. Spider mites are tiny in size (about 1 mm), live on the undersides of leaves, and can be difficult to spot. If you observe the leaves carefully, or shake them on a white surface, you can see small, round bugs. Spider mites can vary in color.
In the similar fashion as mealybugs, spider mites attack the leaves of snake plant. They suck the sap out of the leaves, and cause injuries to the plant. Wounds on leaves make the plant susceptible to more pests. At advanced stages of infestation, leaves will wilt and fall off. It can also lead to the death of plant, if the condition remain untreated.
- Spider mites can be eliminated by washing them off the plant with plain water. You can either wipe the leaves carefully, wash them in shower, or use a hose to spray water on them. Let the snake plant leaves dry completely. Then, increase the humidity around the plant, as it drives the mites away.
- Another possibility to get ride of spider mites is a chemical treatment with insecticides. Insecticides penetrate into the bugs bodies and cause an imbalance in their electrolyte levels. This can ultimately kill the bugs. An insecticidal soap against mites is a widely available remedy.
- A regular soap mixture can also work well instead of using insecticides. Combine a dish soap liquid with water and spray it on the plants. Soapy water suffocates the bugs, kills them as well as their eggs. Make sure to let the plant dry off by keeping it near a draft or in an airy room. Continue this process every 5-7 days, until the mites are gone. This method can effectively help to reduce the bug infestation.
Caterpillars are larvae of butterflies and moths. Both the caterpillar worms and the damage they cause are quite noticeable. So, this infestation is easy to detect being clearly visible to the eye.
Caterpillars damage the leaves by making holes along the sides. Sometimes they also eat the central part of a leaf. If you see holes on the leaves but no worms, it can mean the worms are already gone. Old damage can be identified by a calloused appearance.
- Placing cardboard around the base of your plant seems to get rid of the caterpillars.
- Using Bacillus thuringiensis, a naturally occurring non-toxic soil bacteria, can help fight against this problem. The caterpillars will either die or go away.
Like spider mites, thrips are small (less than 1/20 inches) and thin insects. Adult thrips can have a long fringe of hair around the margins of wings. Different species can be identified with their unique colors. Flower thrips are usually yellow to light brown. On the other hand, thrips that feed mainly on leaves, and found in greenhouses are dark brown to black in color.
You can identify thrips by the appearance of tiny black spots on the plant. They can infest the entire plant, including leaves, stem, and buds. It’s easier to identify them on a white surface. You can shake the plant leaves over a white paper and observe the bugs using a magnifying glass.
Thrips feed by penetrating the cell wall and damaging the plant. This damage on your snake plant is visible in the form of curled or distorted leaves. The leaves may develop silver-gray scars, rough patches, or callused areas where feeding has occurred. Thrips can also transmit viral infections, such as tomato spotted wilt virus to many indoor plants.
- The first step to treat your snake plant infested with thrips, is to remove all the infected leaves. Cut off dead and damaged leaves using a sharp knife or pruner. You can keep the leaves that have started curling, but still look healthy. Dispose of the removed leaves carefully.
- Now, wipe off your snake plant leaves using wet cloth or cotton balls. You can also use rubbing alcohol instead of water. Make sure to thoroughly wipe both the sides of each leaf to remove small bugs and eggs hidden in the crevices.
- If the thrip infestation has widely spread and begun to affect most of your plant, it’s safe to throw away the entire plant. Be careful to discard the plant so that it doesn’t cause cross-contamination and infect your other healthy plants.
The main reason behind fungal infections in Snake plants is the presence of moisture on the leaves. Overwatering a plant can cause Wet and mushy leaves. It can also happen by spilling water on the leaves and letting it sit there. Wet leaves are much more prone to be affected by a fungal disease. Fungal infections can cause a plant to rot and eventually die. Therefore, it is necessary to take precautions to prevent this from occurring.
Red leaf spot (Fusarium moniliforme)
This infection predominantly affects fresh small leaves that are grown in the centre. As the name suggests, it can be easily identified by red colored spots on the leaves of snake plants.
The symptoms of red leaf spot occur initially on the newest leaves of the plant which are within the central whorl. Infection only occurs when this rosette is wet and spores are present. Sunken lesions of irregular shapes usually occur on the leaves. These lesions are reddish-brown, and many times have a yellow border. Under severe spread conditions and continually wet leaves, the lesions coalesce and infection spreads into the plant stem.
- The most important thing to do for controlling this infection is to keep the foliage of the plant dry. Doing this can eliminate the foliar phase of red leaf spot disease.
- Another effective method is to use a fungicide for diminishing symptom expression. If snake plants are treated with fungicides and the leaves are kept dry, growth in the centre may resume in the form of several new buds.
Southern blight (Sclerotium rolfsii)
Although this pathogen attacks all portions of a plant, it is most found on leaves. However, it can also affect the stem and even the soil surface.
Initial symptoms of southern blight are confined to water-soaked, necrotic lesions on leaves. These lesions develop at or near the soil line. In later stages, coarse white round mycelium grows in a fan-like pattern on the leaves or soil surface. Additionally, small sclerotia form almost anywhere on the affected part of the plant or on the soil surface. These sclerotia look like cottony white mustard seeds. And as they mature, they turn darker. Eventually they harden and become dark brown colored. At the same time, the stem of the plant starts wilting and rotting. If all these symptoms are there, your plant is definitely infected by southern blight.
- If the fungus is in initial stages, you can save the plant by wiping off the affected areas by water or alcohol. You’ll also have to replace the soil or at least replace the upper 1-inch layer. Remember to reduce the water amount and keep the soil and leaves dry.
- Chemical control can be very effective for eliminating the spread of disease. Several fungicides are available in the market to address this problem.
- This disease can be avoided by proper watering methods, letting the water drain and maintaining average temperature around the plants.
Soft rot (Erwinia carotovora)
Apart from insects and fungus, snake plants can also be infected by bacteria. Soft rot is a very common problem observed during propagation by leaf cuttings.
Soft rot is easy to recognise by the mushy rot of the lower end of a cutting. Sometimes the plants develop a fishy, rotten odor. Soft rot can occur when you are propagating the plant in water and forget to regularly change the water.
- Eliminating the water on leaves can control bacterial leaf spots. However in most cases it can be impossible to cure.
- Use of bactericides is not recommended due to very poor efficacy.
- Preventative applications are the best to avoid most bacterial infections. An antibiotic solution of streptomycin sulfate (Agri-Strep 21.2%) may help for the control. Strict sanitation and use of clean cuttings are very crucial.
Root knot nematode (Meloidogyne)
Nematodes are microscopic parasites that live in the soil and harm the roots of different plants.
This disease is identified by the occurrence of galls on the roots. In some cases, the root system may be drastically reduced. At the advanced stages, leaves start wilting and the plant growth is stunted.
- Nematicides are effective treatment to get rid of this problem.
- Because the plant roots are harmed, it is recommended to completely destroy nematode infested plants. However, you can still propagate snake plants using leaves, as they remain unaffected.
- It is important to replace the soil or till it few times in winter months.
Weeds are very unlikely to affect indoor or greenhouse-grown plants. Although there still is a possibility. It can come through the soil, airborne seeds entering the ventilation system, windows or water coming from holding ponds.
Finding weeds in your container of snake plants is not a big deal. Just pull it out and remove from the pot. Using a clean soil and following good sanitation practices is enough to avoid this problem in future.
Snake plants are hardy species and can usually be saved from many diseases. In case it is impossible to save a plant, it can still be propagated through healthy leaves or leaf cuttings. However, it is essential to take good care of your plants because strong, healthy plants are less likely to succumb to pests. Preventive measures and routine care of your snake plants will go a long way in preventing such issues in future.
References and Images:
- Mealybug: Photo by Katja Schulz from Washington, D. C., USA / CC
- R.W. Henley, A.R. Chase and L.S. Osborne. Sansevieria Production Guide. CFREC-A Foliage Plant Note RH-91-30
- Spider mites: Photo by CSIRO / CC
- Thrips: Photo by –M.J. 16:36, 7. Jun 2006 (CEST) / CC BY-SA 2.0 DE
- Southern blight: Photo by Lindsey D. Thiessen, Jason E. Woodward / CC
- Nematodes: Photo by Jeffrey W. Lotz, Florida Department of Agriculture and Consumer Services, Bugwood.org / CC BY-SA