As we all know, plants are amazing. When they’re doing well, they are really thriving. However, when they’re not showing signs of happiness, things can spiral and they can spiral FAST. Sometimes an unhappy plant can be due to overwatering or underwatering, too much light or not enough light, or they might need a pot change. The big problems arise when it’s something else... disease or pests. Let’s walk through some common houseplant diseases and pests, and what you can do to resolve the issue if you find that one of your plants has been affected.

Common Houseplant Diseases:

Root Rot
Root rot is a very common issue with houseplants, and it’s usually caused by overwatering. The fungi Rhizoctonia, Pythium, Botrytis, Phytophthora, Alternaria, and Sclerotinia all create root rot.

Signs of root rot:

• Leaf and/or stem wilting 

• Black or brown roots that are soft or slimy

Prevention: 

• Avoid overwatering. It’s better to under water than overwater

• Use clean, sterilized pots

Treatment: 

• If the entire root system isn’t already impacted, cut off any affected roots and repot your plant into a clean pot with new soil

• Treat the affected plant with a fungicide, such as Arber Bio Fungicide

Leaf Spots
Leaf spots can be caused by wet leaves, poor air circulation, and/or overcrowding. Spots may impact part of a leaf or the entire thing.

Signs of fungal or bacterial leaf spots: 

• Brown or black spots on leaves that may have yellow margins or halos, and get bigger with time.

Prevention:

• Make sure your plant is in a well ventilated area that has some sort of air circulation

• Don’t overcrowd- spread your plants out throughout your space

• Avoid splashing water or misting leaves too often

Treatment: 

• Remove any leaves affected

• Fungicides like copper soap or chlorothalonil can be used to prevent further spread and future diseases

Powdery Mildew
Caused by fungi, mildew can be brought on by lack of air circulation or ventilation, low light conditions, or high humidity.

Signs of powdery mildew: 

• White, powdery growth on leaves

• Dry, brown, papery leaf spots

Prevention:

• Avoid keeping your plants in areas with excessive humidity

• Keep plants in areas with good ventilation and air circulation

• Place your plants in areas with natural light nearby

• Avoid overwatering

Treatment:

• Remove affected leaves

• Use a fan to create more air circulation

• Use fungicides to prevent spread and future diseases

Common Houseplant Pests: 

Aphids
Aphids can be green, black, brown, or red. They are small, pear-shaped insects typically 1/16 - ⅛  inches long and feed on new growth or the underside of leaves. 

Signs of aphids: 

• Yellowing or misshapen leaves

• Shiny, sticky secretions on leaves

• Dark spots on leaves

• Aphids can be seen by the naked eye, typically on the underside of leaves, new growth, or along stems

Prevention: 

• Maintain a healthy, happy plant

• Avoid over fertilizing 

Treatment: 

• Neem oil and diatomaceous earth are the best natural treatments

• Rinse off your plant very well with clean water 

• Pick off the aphids by hand

Mealybugs
Mealybugs are small, pale insects with little legs coming out of all sides. They are about ⅛ - ¼ inch long and move very slowly. 

Signs of mealybugs:

• White, waxy material on leaves

• Stunted or distorted growth of leaves

• Mealybugs can be seen by the naked eye, and will usually be found on lower surfaces of leaves or in the axil, where the leaf attaches to the stem. 

Prevention: 

• Maintain a healthy, happy plant

• Regularly wipe down leaves

• Avoid over fertilizing

Treatment: 

• Wipe each mealybug with a cotton swab dipped in rubbing alcohol

• Pick off mealybugs by hand

• Insecticidal soap spray

• If the infestation is advanced, it may be best to discard your plant

Spider Mites
Spider mites are very small pests. They damage plant leaves by sucking the sap, which is usually the initial sign of an infestation because the pests are so small. 

Signs of Spider mites:

• White webbing throughout your plant

• Very small, white speckling on upper surface of leaves

• Yellowing leaves

• Dying plant

Prevention: 

• Avoid overwatering

• Regularly wipe down leaves

Treatment: 

• Spray plants with a forceful amount of water, which will dislodge any spider mites and destroy their webs

• Insecticidal soap, neem oil 

Fungus Gnats
Somewhat resembling typical gnats, fungus gnats are about ⅛ inch long and adults actually do not feed on plants. They are more of just a frustrating nuisance to people.

Signs of fungus gntas:

• Small, black insects flying around near your plants

• Small, black insects crawling or flying around the soil of your plant(s)

• Whitish larvae with black heads in soil, about ¼ inch long

• Young plants may be show signs of dying

Prevention:

• Avoid overwatering. Fungus gnats thrive in consistently wet soil (they lay their eggs in the top 2-3 inches of soil)

• Avoid using material that has not fully composted with your soil, as it can often be infested with fungus gnats

Treatment:

• Neem oil every 7 days until infestation is gone

• A 1:2 ratio of hydrogen peroxide and water every 7 days until infestation is gone (spray soil only)

• Empty water saucers after watering plants

Scale
There are two types of scale; armored and soft. Adults do not have legs, and can appear flat or bumpy, waxy and colored between 1/16– to ½-inch in diameter. They kill plants by feeding on their sap.

Signs of scale:

• Round, slow moving or immobile specks along the stems or undersides of leaves (can be on top of leaves as well).

• Black, sooty mold on leaves and/or stems (caused by scale secretion called honeydew)

Prevention: 

• Spray neem oil on plants during winter months, or late winter/early summer. 

Treatment:

• Small infestations can be treated by scraping scales off plants 

• Products containing neem oil extract or canola oil can be used

• Young scales, also called crawlers, can be eradicated using insecticidal sprays or soaps

Whiteflies
Whiteflies are small, flying pests about 1/10  to 1/16 -inch long with a powdery white appearance often resembling a very small moth.

Signs of whiteflies:

• Stunted plant growth

• Yellowing, dying leaves

• Small, white fly-like bugs flying around your plant

• White, powdery and sticky substance on the underside of leaves (whitefly secretion, honeydew)

Prevention: 

• If you already have an infestation on one plant, prevent the spread by isolating the affected plant in a completely different area, far from other plants

• Spraying plants with neem oil every few months

Treatment: 

• Wash the affected plant thoroughly with insecticidal soap

• Add Imidacloprid granules to soil 

• Spray affected plant well with neem oil

Sources:

• https://hgic.clemson.edu/factsheet/houseplant-diseases-disorders/

• https://hgic.clemson.edu/factsheet/common-houseplant-insects-related-pests/

• https://hortnews.extension.iastate.edu/diagnosing-houseplant-problems-diseases