1. Scale Insects
Symptoms: Sucking insects that attach to the underside of leaves, in leaf axils, on pseudobulbs, and on rhizomes. Severe infestations cause chlorotic areas on leaves, which yellow and fall prematurely.
Varieties:
- White Scale (Boisduval): main enemy of Cattleya. Males appear as white cottony masses, females lay eggs under circular white shields.
- Hard Scale: forms a conical brown structure that protects the animal underneath.
- Soft Brown Scale: pale yellow or dark brown, with oval or circular shells on leaves, flowers, flower spikes, pseudobulbs, and roots. Produces honeydew (sticky substance), unlike hard scales.
Treatment: For a few scales, use a cotton swab soaked in isopropyl alcohol or a pesticide to physically remove them. For severe infestations, apply pesticide during the crawler stage and repeat after 2 weeks. Spray all surfaces, especially the underside of leaves. Active ingredients: Chlorpyrifos and Buprofezin.
Prevention: Remove old leaf and flower sheaths to eliminate hiding places. Carefully check new plants before adding them to your collection.
2. Mealybugs
Symptoms: Sucking insects that attack any part of the plant, tending to hide in the junctions between leaves and stem. Severe infestations cause chlorotic areas, yellowing, and premature leaf drop.
Treatment: For a few mealybugs, physically remove them with a cotton swab soaked in isopropyl alcohol or a toothbrush with pesticide. For severe infestations, apply pesticide and repeat after 2 weeks. Spray all surfaces, especially the underside of leaves and leaf axils.
Prevention: Remove old leaf and flower sheaths. Carefully check new plants before adding them to your collection.
3. Thrips
Symptoms: Very small sucking insects that feed on flowers and leaves, transmitting diseases from one plant to another. Infested buds may not open and flowers can be deformed with dark spots. Leaves may appear stippled, silvery, or discolored.
Treatment: Apply pesticides following label instructions. Repeat applications as thrips can remain hidden or be reintroduced from other flowers in the environment.
Prevention: Keep thrips' preferred hosts (flowers, citrus, gardenias, eucalyptus) separate from orchids. Remove weeds, plant debris, and old substrates. Dispose of withered flowers by sealing them in a closed bag. Keep grass mowed.
From left: Springtail (harmless, found in the saucer or substrate), Fungus Gnat (found in moist or decaying substrates, flies when watered), Thrips (on leaves and flowers with characteristic damage). The differences are visible to the naked eye: body shape and antenna length.
4. Mites
Symptoms: Mites (arachnids, not insects) feed on the underside of leaves. They may be visible as tiny red or brown pests, sometimes with webbing. The upper side of damaged leaves may have a silvery sheen that becomes pitted and brown. Leaves appear streaked, speckled, or spotted.
Varieties:
- Two-spotted spider mite / red mite (Tetranychidae): causes stippled chlorotic spots and webbing under the leaf in severe infestations.
- Flat mites (Tenuipalpidae): feed on the upper side of leaves creating a cratered appearance, without webbing.
- Broad mites (Tarsonemidae): microscopic, the first symptom is chlorotic discoloration.
Treatment: Spray the upper and lower surfaces of leaves with a mixture of 1 part isopropyl alcohol + 1 part all-purpose cleaner + 2 parts water. Alternatively, a 2% oil-in-water solution with a dash of dish soap. You can alternate applications of 2% oil solutions and 2% soap solutions. Alternatively, use a miticide following label instructions. During warm weather, new generations mature every 6 days: repeated applications will be necessary.
Prevention: Mites appear during hot, dry weather. Increase humidity and, if possible, lower the temperature.
5. Aphids
Symptoms: Sucking insects that attack buds, flowers, and new growth, transmitting diseases from one plant to another. Buds and flowers may fail to open and leaves may have a sticky deposit.
Treatment: Remove aphids with a jet of water. Treat with a pesticide following label instructions.
6. Whiteflies
Symptoms: Small, moth-like insects that attack buds, flowers, and new growth. The characteristic sign is a cloud of tiny white insects that rise from the plant when it is moved or touched.
Treatment: Spray with pesticides following label instructions. Repeat applications at 4-day intervals until whiteflies disappear.
Prevention: Good hygiene, weed removal, and keeping host plants separate from orchids.
7. Snails and Slugs
Symptoms: These mollusks leave holes and notches on leaves, flowers, and roots, and can gnaw on growing tips. They are nocturnal pests that move on a layer of mucus: the slime trail is a clear sign of their presence.
Treatment:
- Place chemical baits in the growing area.
- Spread ash or diatomaceous earth on horizontal surfaces to create a barrier (water deactivates them).
- Place shallow containers with beer to attract and drown pests, removing them the next day.
Regular applications will be necessary as irrigation can disperse these control methods.
8. Caterpillars
Symptoms: Caterpillars are the juvenile stage of moths and butterflies. Although not very common, they are voracious and can cause severe damage to flowers and leaves in a short time.
Treatment: Manually remove caterpillars from the plant, checking the underside of leaves. Bacillus thuringiensis (Bt) is a safe and ecological natural bacterium that can be sprayed in the growing area following label instructions.
Prevention: Keep the growing area clean of fallen leaves and debris, which can provide shelter for pests and their eggs.
9. Ants
Symptoms: Ants cause little direct damage. Their presence is usually a sign of sucking pests that produce honeydew, a substance that attracts ants.
Treatment: If you notice ants, check plants for aphids, mealybugs, scale insects, and mites, and treat them accordingly.
Prevention: Keep plants and the growing area free of sucking pests to reduce the presence of honeydew.
10. Cockroaches and Grasshoppers
Symptoms: Cockroaches and grasshoppers cause damage by feeding on flowers, roots, and new growth.
Cockroach Deterrent: Distribute cockroach baits in the growing area, or prepare a paste of boric acid, sugar, and flour mixed with water to apply in every crack and corner. Do not put this mixture directly on plants.
Grasshopper Deterrent: Partially bury cans filled with a mixture of molasses and water and remove drowned insects the next day.
11. Fungus Gnats
Symptoms: Adults are active on the substrate surface and fly easily when watered or touched. Larvae are white or translucent with black heads, clustered around decaying roots. Their presence is often an indicator of overly moist or degraded substrate.
Treatment:
- Yellow sticky traps: excellent for catching adults.
- Adjust watering and ensure the substrate drains well and is not excessively decayed.
- Bacillus thuringiensis israelensis: effective against young larvae, active for about 48 hours. 2–3 applications may be needed. Do not use with fertilizers or fungicides containing copper or chlorine.
- Parasitic nematodes (Steinernema carpocapsae and Steinernema feltiae): applicable as a drench solution, very effective.
- Predatory mite Hypoaspis miles: attacks fungus gnat larvae and also feeds on thrips pupae and other pests.
Prevention: Keep the substrate well-draining and repot frequently if using a heavy watering regimen.
