Most of us have peace lily houseplants. They can only live outside all year in tropical climates. Spathiphyllums are rarely troubled by diseases when grown indoors or in a shady spot outside in the summer. The insect pests that annoy them on occasion are the usual suspects, such as aphids, mealybugs, and spider mites.
The first line of defense against pests and diseases is to keep the leaves of your spathiphyllum clean. Because the large, dark green leaves attract dust and the flowers shed pollen, a periodic leaf washing allows you to inspect your plant for problems. It will be easier to treat a disease or insect problem if you detect it early.
Here are the diseases and pests that might trouble your peace lily.
Peace Lily Diseases
Peace lilies rarely suffer from disease when properly cared for. With the exception of Dasheen Mosaic Virus, these diseases are preventable through cultural practices:
- Plant in a clean pot with drainage holes.
- Always use a high-quality potting mix that’s well-draining.
- Water the soil, not the leaves.
- Water deeply and thoroughly, but not too frequently.
- Empty the water from pot saucers so that pots don’t sit in water.
This is the most common killer of spathiphyllum. The pathogens that cause root rot in peace lilies are cylindrocladium and pythium. Although a plant lab can assist you in determining which fungal disease you have, because they both cause the same problem, an exact diagnosis is not required. When root rot attacks your spathiphyllum, you’ll notice the following symptoms:
- The soil is very wet or soggy.
- The leaves are yellow and wilting.
- When you lift the plant out of the pot, you see that the roots are mushy, or black, or non-existent.
Root rot can quickly kill a plant. Because root rot occurs beneath the soil, it is frequently too late by the time it is discovered. However, if you act quickly, you may be able to save your plant. Remove the plant from the pot and allow any excess water to drain. Examine the roots after removing the saturated soil from the root ball. Your plant can be saved if there are still healthy roots.
With a clean, sharp pair of pruners or scissors, cut away the dead roots. Repot your peace lily in a new pot with fresh potting soil. Keep it out of direct sunlight for a few months and don’t fertilize it. Before watering, make sure it really needs it, and hope for the best!
Leaf Blights and Spots
Leaf blights and spots are fungal diseases that thrive in high moisture levels. If the pathogen is present in your potting soil, it may contaminate the leaves. The pathogen can take hold if the leaves become wet and remain wet. When a plant part becomes infected, the disease spreads quickly.
Whether it’s cercospora, fusarium, or another foliar disease, prevention is the best medicine. A good commercial potting mix should not contain pathogens, so choose a reputable brand. Use high-quality ingredients when making your own mix. Water the soil, not the sky.
Fungicides are most effective as a preventative measure and should be used before a disease manifests. While we can predict the appearance of outdoor fungal diseases like powdery mildew, it is more difficult to do so with indoor plants. Furthermore, you may not want to spray these chemicals inside.
Dasheen Mosaic Virus
This virus is Infects plants in the Araceae family, including spathiphyllum, taro, alocasia, philodendron, and colocasia. Mosaic viruses cause color breaks and streaks on leaves, primarily along veins. Plant viruses have no known cures. These diseases are inherent in the plant, so purchase your peace lily from a reputable grower.
Aphids spread this virus from peace lily plant to peace lily plant. Once infected, a plant will always be infected. You can’t just cut off the diseased part and expect everything to be fine. You can discard the plant and try again, but if you like the color breaks and streaks, a peace lily can live with the virus for a long time. Don’t give infected plant cuttings or divisions to others.
Peace Lily Pests
Peace lilies are generally pest-free, so inspect the rest of your houseplant collection if you find insect pests on your plant. When you buy a houseplant, you may bring an insect infestation home with you, so inspect it carefully before purchasing and keep it separate from the rest of your plants until you are certain it is bug-free.
Most insect problems should be avoided if you inspect and dust or wipe down the leaves of your houseplants on a weekly basis.
Spider mites, mealybugs, aphids, and fungus gnats are examples of indoor pests. Most of these can be controlled by scouting before populations become too large, wiping them away with water or rubbing alcohol, or applying insecticidal soap labeled for indoor use.
Spider mites suck the juices out of plant leaves, giving them a mottled appearance.
Despite their small size, they are easily identified by the fine webbing they produce. They thrive in warm, dry conditions and are common in indoor gardens during the winter. Keeping the humidity around 50% can help keep spider mite populations under control. Spider mites can be removed with a strong blast of water from a garden hose (or the kitchen sink sprayer).
Mealybugs consume plant juices as well. These cottony, white pests are about the size of a grain of rice and live in colonies, usually in leaf crotches and on the undersides of leaves. If the infestation is minor, a cotton swab dipped in rubbing alcohol and dapped on the individual pest instantly kills it. Keep an eye out for mealybug eggs, which are resistant to pesticides and hatch a week after being laid.
Aphids also feed on plant juices. They, too, live in colonies and can be found climbing up and down leaves and stems. They can be green, red, white, brown, or black in color. When the infestation is severe, they excrete a sticky “honey dew” (poop) that attracts sooty mold. Keeping your plants clean greatly aids in keeping these pests at bay.
Fungus gnats are harmless, but they can be bothersome. They appear in wet soils and can be a problem with peace lilies, which prefer moist conditions. The gnats vanish when the soil dries out. There is no need for any additional corrective action.
Slugs, snails, and caterpillars may attack peace lilies if grown outside. The ragged holes and chomped leaves indicate that they have been at your plants. Remove the offenders with gloved hands and place them in a bucket of soapy water. To keep these soft-bodied pests at bay, sprinkle diatomaceous earth around your outdoor spathiphyllums. Commercial slug baits, as well as a saucer of stale beer, work well, and don’t forget about birds and parasitic wasps.