1. COCCIDIA
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Symptoms : Coccidia are sucking insects that attach and feed on the undersides of leaves, in leaf axils, on pseudobulbs, and on rhizomes. They often hide under older leaves and the sheaths of pseudobulbs. Severe infestations cause chlorotic areas to appear on leaves and plant surfaces, which turn yellow and may darken, causing premature leaf drop.
Variety:
•The white mealybug (Boisduval) is the main enemy for Cattleya growers. Mature males appear as masses of white cotton, while mature females lay eggs under white circular shields. The larvae, called crawlers, are the juvenile stage that emerge from under the shield until they find a new place to settle.
•The hard coccid is another type of armored coccid that eventually forms a brown conical structure that protects the animal underneath.
•The soft brown mealybug is pale yellow or dark brown in color, with oval or circular shells that appear on leaves, flowers, flower spikes, pseudobulbs, and sometimes on rhizomes and roots. Soft mealybugs produce "honeydew" (a sticky substance), while hard mealybugs do not.
Treatment: If there are only a few coccidia, use a cotton swab soaked in isopropyl alcohol or a pesticide (following the label instructions) to physically remove the coccidia. For more severe infestations, apply the pesticide during the crawler stage and repeat the application two weeks later. Be sure to spray all surfaces of the plant, especially the undersides of leaves and leaf axils. Some active ingredients used are chlorpyrifos and buprofezin.
Prevention: Remove old leaf and flower sheaths to eliminate coccidia hiding places and make inspection easier. Carefully inspect new plants before adding them to the growing area.
2. COCHINEAL INVISIBLES
Symptoms: Scale insects are sucking insects that attack any part of the plant, but they tend to hide in the junctions between leaves and stems. Severe infestations can cause chlorotic areas to appear on leaves, which may darken, yellow, and drop prematurely.
Treatment: If there are only a few mealybugs, physically remove them using a cotton swab soaked in isopropyl alcohol or a toothbrush soaked in pesticide (follow the label instructions). For more severe infestations, apply the pesticide and repeat the treatment after two weeks. Be sure to spray all surfaces of the plant, especially the undersides of leaves and leaf axils.
Prevention: Remove old leaf and flower sheaths to eliminate hiding places and make inspection easier. Carefully inspect new plants before adding them to the growing area.
3. THRIPS
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Symptoms: Thrips are tiny sucking insects that feed on flowers and occasionally leaves, and can also transmit diseases from one plant to another. Infested buds may fail to open, and flowers may appear deformed with dark spots resembling waterlogged areas. Leaves may appear mottled, silvery, or discolored. Roots may be damaged by thrips feeding on growing tips.
Treatment: Thrips are among the most difficult orchid pests to control. They are small and hard to spot, mobile, spend part of their life cycle in the soil, and feed primarily on flower parts (where systemic insecticides cannot reach them). They hide in flowers, buds, and leaf buds, making them difficult to detect and treat with pesticides (following label instructions).
Furthermore, they reproduce rapidly in warm greenhouses, can be present in multiple stages of their life cycle (from egg to adult), live on many different host plants, and are resistant to various insecticides. Most adults are females that lay eggs in plant tissue, particularly flowers and leaves. Repeated applications will be necessary, as thrips can remain hidden on the plant or be reintroduced from other flowers into the surrounding environment.
Prevention: Good hygiene helps prevent infestations, as does keeping thrips' preferred hosts (flowers, citrus trees, gardenias, eucalyptus, etc.) separate from orchids. Remove weeds, plant debris, and old substrates from the growing area. Remove old mother plants, which can be a source of thrips and viruses. Remove faded flowers to reduce the number of adults and eggs, sealing them in a closed bag or container. Thrips lay eggs in grassy areas, so it's helpful to keep the grass cut and control weed growth.
Be careful not to confuse springtails and sciarids with thrips!
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Springtails are usually found floating around in the saucer, pot cover, or substrate; they are harmless to the plant. Sciarids are found in moist or degraded substrates; they feed on decaying roots. When plants are watered or even slightly knocked, they all take flight. This is often a symptom of overwatering or rotting roots. Thrips, on the other hand, are found on the leaves and flowers of the plant, causing characteristic damage! On the left, you can see a springtail, in the center, a sciarid, and on the right, a thrips. As you can see, there are some differences visible even to the naked eye, such as the shape of the body and the length of the antennae. I hope this helps you avoid confusion!
4. MITES
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Symptoms: Spider mites are not insects, but are part of the arachnid family. Spider mites usually feed on the undersides of leaves and can be
Found underneath as small red or brown parasites. You may need a magnifying glass to see them. The undersides of leaves may have webs and brown spots due to mite excrement. The upperside of a damaged leaf may have a silvery sheen that eventually becomes sunken and brown. Leaves may appear streaked, dotted, or spotted due to chlorophyll deficiency.
Orchids with thin or soft leaves are more susceptible to spider mite damage than those with thicker leaves, but no variety is completely immune.
Variety:
• The two-spotted spider mite, or red spider mite (Tetranychidae), causes chlorotic or stippled spots at each feeding site, as chloroplasts are sucked out along with the plant sap. Leaves eventually develop a spotted appearance with webbing underneath in severe infestations.
• Flat mites belong to the Tenuipalpidae family, which often feed on the uppersides of leaves, creating a cratered appearance due to empty, collapsed leaf cells. The feeding of flat mites on thin leaves, especially the undersides, is similar to the stippling caused by red spider mites, but without the webs.
• Large mites (Tarsonemidae) are microscopic and the first symptom is a chlorotic discoloration.
Treatment: Try spraying the upper and lower surfaces of the leaves with a homemade mixture of 1 part isopropyl alcohol, 1 part all-purpose cleaner (such as 409) or Murphy's Oil Soap, and 2 parts water. Another option is a 2% oil solution (Johnson's baby oil or vegetable oil) in water with a splash of dish soap (Ivory or Palmolive). This equates to about 5 tablespoons of oil per gallon of water. You can alternate applications of 2% oil and 2% soap solutions. Plants can also be sprayed with a miticide, following the label instructions, paying particular attention to treating the undersides of the leaves. During warm weather, new growths mature every 6 days, so repeated applications will be necessary.
Prevention: Mites appear during hot, dry weather. Increasing humidity and leaf moisture and, if possible, lowering the temperature helps prevent infestations.
5. APHIDS
Symptoms: Aphids are 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 from the plant with a jet of water. Plants can be treated with a pesticide, following the instructions on the product label.
Additional Information: The honeydew excreted by aphids and other plant-sucking insects attracts ants and is an ideal environment for sooty mold. If sooty mold is present, inspect the plants for aphids, scale insects, shield bugs, and mites.
6. WHITE FLIES
Symptoms: Whiteflies are small, moth-like insects that attack buds, flowers, and new growth. Their distinctive sign is a cloud of tiny white insects that rise from an infested plant when it is moved or touched.
Treatment: Plants can be sprayed with pesticides, following the instructions on the label. Repeat applications at four-day intervals until the whiteflies disappear.
Prevention: Good hygiene and weed control help prevent infestations, as does keeping host plants separate from orchids.
7. SNAILS
Symptoms: These mollusks leave holes and indentations on leaves, flowers, and roots and can nibble away growing tips. Even buds may show damaged areas. These nocturnal pests move on a layer of mucus, and a trail of slime is a clear sign of their presence.
Treatment: Chemical baits can be placed in the growing area.
Ash and diatomaceous earth can be spread on horizontal surfaces to create a barrier, although water deactivates them. Beer can also be used in shallow containers, placing it in the growing area to attract and drown the pests, which should be removed the next day. Regular applications will be necessary, as irrigation can disperse these control methods.
8. CATERPILLARS
Symptoms: Caterpillars are the juvenile stages of moths and butterflies. Although they aren't very common, they are voracious and can cause serious damage to flowers and leaves in a short time.
Treatment: Caterpillars can be removed from the plant by hand and destroyed; check the underside of leaves for their presence.
Bacillus thuringiensis (Bt) is a natural bacterium that targets insects and is a safe and environmentally friendly product that can be sprayed in the growing area following the instructions on the label.
Prevention: Keep the growing area clear of fallen leaves and debris, which can provide shelter for pests and their eggs. Keep the garden free of caterpillars.
9. ANTS
Symptoms: Ants cause little direct damage. Any visible damage is most likely due to sucking parasites, which cause the plant to secrete honeydew (essentially plant sap), a substance that attracts ants.
Treatment: If you notice ants, check your plants for aphids, mealybugs, shield bugs, and spider mites, and treat them accordingly.
Prevention: Keep your plants and growing area free of sucking pests to reduce the presence of honeydew, although healthy, vigorous orchids may sometimes secrete honeydew naturally.
10. COCKROACHES AND GRASSHOPPERS
Symptoms: Beetles and grasshoppers cause damage by feeding on flowers, roots, and new growth.
Cockroach Deterrent: You can distribute cockroach bait throughout the growing area or prepare a paste of boric acid, sugar, and flour mixed with water, and apply it to every available crevice and nook. Avoid applying this mixture directly to the plants.
Grasshopper Deterrent: Partially bury jars filled with a mixture of molasses and water and remove the drowned insects the next day.
11. SCIARIDES
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Symptoms: Over time, growing medium degrades, and it's interesting to note that there's an insect that can be used as an indicator of poor orchid care. Probably every orchid grower has at least one in their collection: fungus gnats. Fortunately, for orchid growers, these little flies are usually just a nuisance.
Adult sciarids are usually the first life stage of these insects to be observed. Adults are active on the surface of the soil, often scurrying along the edge of the pot. They fly easily and are often found near windows.
The larvae are white or translucent, with a thin body and black head. They usually congregate around decaying roots and fungal lumps in the soil.
Why do we often see them near our plants?
IT'S NOT BECAUSE THEY FEED ON YOUR PLANTS! THEY'RE HARMLESS!!
They're common because their larvae feed on fungi that grow in overly moist or wet, warm, and rapidly decomposing soil. Usually, the larvae feed only on fungi. However, they can also feed on seedlings, dying, and decaying tissue such as roots, and will quickly devour a leaf resting on the surface of moist soil. So, if your orchid is healthy, it's not at risk!
Treatment: Fungus gnats are generally easy to manage and can be controlled in most orchid collections. The yellow sticky cards sold for monitoring and controlling aphids and whiteflies are excellent for catching fungus gnats. The larvae are easily controlled by adjusting watering and ensuring the orchid substrate is not excessively decomposed and drains well. This may require frequent repotting if you use a heavy watering regimen.
If these cultural methods are ineffective, alternative treatments may be necessary. However, the use of insecticidal irrigation to control larvae is not recommended except as a last resort. The use of bacteria, nematodes, and predatory mites is highly effective in greenhouses and can be effective in large collections.
Bacterial treatment is most effective against young larvae at the beginning of the crop cycle and uses Bacillus thuringiensis israelensis. It is only effective for about 48 hours, so 2-3 applications may be necessary in case of heavy infestations. The use of this bacterium is not recommended in conjunction with fertilizers or fungicides containing copper or chlorine. It has no effect on adult midges.
Parasitic nematodes are also useful for controlling midges. They enter the insect's body and multiply internally. Nematodes complete their life cycle in a few days, producing large numbers of infective nematodes that will continue to search for new hosts. These beneficial nematodes can be applied as an irrigation solution to the growing medium and soil. Two species available for use are Steinernema carpocapsae and Steinernema feltiae.
Finally, a small predatory mite, Hypoaspsis miles, also attacks fly larvae. This mite is long-lived, usually persisting as a scavenger on dead insects while continuing to search for fungus gnat larvae. It also feeds on thrips pupae and other parasites.
Collaboration between Criplant and Giulio Celandroni Orchids
Info: St. Augustine Orchid Society
