University of Maryland Extension

Diagnostic Chart: Houseplant Problems

leaf spots on houseplant leaves

Houseplant Problems

SymptomsPossible CausesControl/Comments
Plant wilting

Overwatering or lack of water: overwatering can cause root rots. Healthy roots should be light-colored and firm.

Use a well-drained, soilless potting media labeled for houseplants. Water should be able to drain from the bottom of containers.
Severely damaged plants should be discarded.

Plant wilting

Various root rots: pull plant out of the pot and observe roots for discoloration. Diseased roots will appear dark and soft.

Remove diseased plants from their pots, cut
out infested portions (rotten), and replant
remaining healthy sections. Take cuttings and root them in sterile potting mix.

 

Plant wilting

Stem cankers: discolored areas on stem

Prune out affected areas. 

Leaf yellowing, foliage fades, yellows browns or wilts

Aphids: small soft-bodied insects found on leaves, stems and flower buds.
Spider mites: minute pests that feed on lower leaf surfaces, webbing may be visible.
Mealybugs: white cottony insects.
Whiteflies: adults are tiny white insects that fly from the plants when disturbed. Immature stages found on lower leaf surfaces.
Brown soft scale and hemispherical scale: raised black or brown bumps on leaves and stems.

Regularly rinse plants with water to keep down pest problems. Use a registered houseplant spray to control pests. Plants damaged by heavy insect or mite feeding can be injured by insecticidal sprays. Severely damaged plants should be discarded.

Leaf yellowing, foliage fades, yellows browns or wilts

Root rots: discolored and softened roots.

Remove diseased plants from their pots, cut out portions (rotten), and replant remaining healthy sections. Take cuttings and root them in sterile potting mix.

Leaf yellowing, foliage fades, yellows browns or wilts

High soluble salts.

Leach soil at least three times with pot volume of fresh water.

Bleached or whitened leavesExcessive light or sunburn.Acclimate plants slowly to higher light intensities, especially when moving them outdoors in the summer.
Fine stippling
(numerous tiny dots caused by spider mite feeding)
Spider mites: minute pests that feed on lower leaf surfaces, webbing may be visible.Regularly rinse plants with water to keep down spider mite problems.
Use a registered houseplant spray to control mites. Plants damaged by heavy mite feeding can be injured by insecticidal sprays. Severely damaged plants should be discarded.
Leaf spots and leaf blotchesWater spots, sunburn, various fungi, bacteria.Do not splash water onto plants with fuzzy leaves such as African violets. Remove spotted leaves and improve air circulation to reduce leaf diseases. 
Leaf or shoot blackeningCold Injury: symptoms may continue for up to a week after exposure.Protect plants from temperatures below 50° F.
Leaf scorchAbiotic stresses (not related to disease or insects) such as over-fertilization, high soluble salts, lack of water: scorching symptoms can occur along leaf margins or between veins.Leach excessive fertilizer from potting mix by flushing with water or repot with fresh potting media.
Stunted, twisted and distorted plant growthAphids: small soft-bodied sucking insects. Cyclamen mites: predominately a pest of flowering plants. New growth is affected first. Viruses: foliage appears mottled green and yellow. Plants may be stunted.Aphids can be controlled with a stream of water or with a registered insecticide. 
Plants infested with cyclamen mites or infected with viruses should be discarded. 
Leaf mottlingViruses: foliage appears mottled green and yellow. Plants may be stunted.No effective treatment, discard infected plants.
White powdery coating on leavesPowdery mildew fungi: grows on the leaf surface.Provide better air circulation and pick off infected leaves. Spray with a registered fungicide if disease is severe. Check horticultural oil labels for powdery mildew control listings.
Fuzzy gray growth on leaves or flowersGray mold: frequently infects old faded flowers or older, lower foliage.Provide better air circulation. Pick off infected flowers or leaves. Remove old blooms or foliage.
Fluffy white waxMealybugs: white cottony insects may occur on foliage, in leaf axles, leaf sheaths, roots, and bud scales.Use a registered houseplant spray to control mealybugs or use a cotton swab dipped in alcohol to kill individual mealybugs.
Leaves eaten or chewedCheck plants that have been outside for the summer for pests such as caterpillars, leaf feeding beetles, weevils, grasshoppers, crickets, slugs, and earwigs.Handpick pests and repot plants before moving plants inside.
Few or no flowersLow light levels, excessive fertilizer, cyclamen mites.Increase light levels by relocating plants closer to a light source or add additional artificial light sources. Cyclamen mite infested plants should be discarded.
Spindly growthLow light levels or excessive fertilizer, (high soluble salts).Increase light levels by relocating plants closer to a light source or add additional artificial light sources. Reduce fertilizer applications during winter. Irrigate from the top of the pot to leach out excess fertilizer salts.
Poor growthPoor growing conditions, insects and diseases.Follow recommended practices.
Flying insectsWhiteflies: tiny white insects flying around plants.
Fungus gnats: tiny black flies flying near plants or near light sources.
Use a registered insecticide for whiteflies.
Allow potting media to dry between waterings.
Insects in potting mediaAnts, sowbugs, springtails earwigs, millipedes, slugs, slugs: often brought in from outside when relocating plants from outdoors.Repot plants with fresh potting media. Beneficial nematodes may be used to control fungus gnat larvae.

Based on HGIC publication HG 60 IPM Series: Houseplants, authors Dave Clement, Ph.D., Extension Specialist, Plant Pathology and Mary Kay Malinoski, Extension Specialist, Entomology.

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