A complete care guide on treating the most commonly seen pest infestations and diseases in orchids

You have purchased orchids and are tending to their needs regularly, looking forward to a good blooming season, but suddenly one morning, you notice your sprightly orchid not so buoyant anymore. And your first instinct is to check:

What’s wrong with my orchid? How did it happen?

How can I resolve this issue and save my orchid?

Your first orchid casualty will have you brooding over your loss. I remember being distraught during my first year as an orchid hobbyist and frantically trying to put things right, especially as my Miltoniopsis fell prey to rot issues, Phalaenopsis suffered crown and stem rot,  my Nelly Islers couldn’t grow in my warm climate, and my Cattleya were time and again attacked by scale. Not to forget the slug and spider mite infestations that had me on edge until I ensured that all my plants were free of these pests. Whew! That was indeed a lot of hard work.

As alarming as it can get, do not get unduly hassled. A lot of problems can be resolved easily and let’s not forget that orchids in the wild live on for 100 years and more and propagate without any special care.

With a proper care routine and timely remedial treatment, your orchids will not only remain healthy, but will reward you with beautiful blooms year after year.

Before we get on to the specifics of these maladies, I would like to stress on the fact that the more time an orchid spends distressed and diseased, the longer it will take for it to bounce back. These conditions also lead to a setback for the orchid, leading to complications such as bud blast and in some cases, the orchid skips the bloom cycle altogether, which can be disappointing after the hard work that you have put in all year round.

 It is best to react with immediate effect and apply remedial treatment so that its chances of survival improve significantly.

Regularly scrutinize your orchids and check for signs of stress and pest infestation or other types of microbial infections while you are watering your orchids, fertilizing them, repotting them and grooming them.

At the outset, let us understand what are the common issues seen in orchids and what caused them.

Common diseases in orchids and their causes

Symptoms	Type of Malady
Wrinkled, dull, limp and leathery leaves	Root system damage
Patchy chlorosis on leaves, with undersides of leaf turning black or brown	Spider mite infestation
Crown and stem rot (soft rot)	Bacterial and fungal infections
Dehydrated leaves and lack of signs of growth; purple ring visible on cross-section of rhizome	Fusarium wilt
Scaly spots and patches	Biosduval scale
Powdery white patches	Mealy bugs
Leaf spots	Bacterial and viral infestations
Black spots on flowers	Botrytis – bacterial infestation of leaves and flowers
Strips and ring like patches on leaves	Viral infections

Below is a brief overview of issues commonly faced by orchid hobbyists, with their remedial treatment and cure:

ROOT SYSTEM DAMAGE

Symptoms: Limp and Leathery leaves with no signs of growth. This is a clear sign of a stressed out orchid.

Causes: Below are the most common causes of root system damage:

• Root system decay – Often the bane of overzealous watering by orchid hobbyists, this issue occurs due to excessive moisture and fertilizer application, especially if there is inadequate aeration and improper drainage. These conditions encourage the growth of bacteria and fungi, which attack the plant’s roots and decay them, thus affecting the uptake of moisture and nutrients from the plant.
• Inadequate moisture – Occurs if the orchid is subjected to prolonged periods of dryness between watering. This could also be caused by exposure to bright direct sunlight and air drafts coupled with inadequate watering.
• Snail infestation – You need to be wary about this right from the time you get home your newly purchased orchid. Watch out for signs of dehydration coupled with chewed up roots and tender new growths at the base of the plant.                                    
• Physical damage during repotting – During repotting, sometimes the root system remains stuck to the original pot and potting media, especially when terracotta pots and wood mounts are used for growing your orchids. You need to gently pry open the roots in such cases. This leads to bruised and broken roots, which become vulnerable to bacterial and fungal rot, when repotted in fresh media. If the orchid does not have a healthy root system, then it does not absorb adequate moisture, thereby leading to dehydration. Since the moisture is not taken up by the plant, the medium remains excessively moist for long time, leading to decay of the remaining healthy roots.

Remedy:

• Avoid excessive watering of orchids. Provide a good wet-dry cycle as per the requirements of the orchids. Also ensure that the root system receives adequate aeration by using a coarse medium and perforated pots. To learn more about these aspects, read my post Everything you wanted to know about ORGANIC MEDIA
• Orchids require adequate moisture and humidity for their healthy growth. So frequent prolonged dry spells between watering that lead to severe dehydration should be avoided. Ensure your orchid responds well to the care routine you are providing and optimise it to get better results.
• Chewed up new roots due to snail or slug damage can be a big setback for your plant. Unpot the orchid and disinfect the root system with hydrogen peroxide and then repot your orchid in fresh medium at the earliest.
• Roots invariably end up getting damaged during repotting. To reduce this damage, you can moisten the roots and pry them gently using a thin, blunt knife. To prevent a setback for the plant due to repotting, the plant needs to put out fresh roots at the earliest. So, unless the plant is unhealthy and needs immediate repotting, it is always a good idea to repot when the plant gives out new shoots and roots. This will allow the plant to recuperate fast despite the setback.

Pest infestation

SPIDER MITE INFESTATION

Symptoms: Spider mites live and feed on the undersides of orchid leaves, scarring the leaves. They can easily be detected by looking out for a white sheen on the underside of leaves caused due to chlorosis (destruction of chlorophyll), which turns rough and brownish-black later.

Caused by spider mite infestation during dry, dusty and warm weather conditions, spider mites are extremely tiny insects that are red or brown in colour. Look out for webs and scan for mites, which can be seen under a magnifying glass or you could zoom in with your phone camera and you will spot them moving about. Alternatively, wipe the area with a damp cotton ball and if you spot tiny red dots, then this is a confirmation of spider mite infestation.

Treatment: As a conservative treatment, you can spray a solution of 2 drops of neem oil with 1 drop of dishwash liquid in 500ml of water. Spray the plants to cover all possible surfaces. Ensure that the plants are placed under a fan to ensure that the excess liquid dries off quickly and does not pool in crevices, leading to further complications of stem and crown rot.

Another more aggressive approach would be to spray a suitable miticide such as horticultural oil that is made from vegetable oil or mineral oil (pick one from your local horticultural shop or search for it online), paying particular attention to manufacturer’s instructions (use below recommended dilution) and taking adequate safety precautions. You can test it on a leaf before applying on the entire plant. Repeat application after two weeks until the mites disappear totally.

Prevention: As a preventive measure, do not allow your orchids to remain in dry and dusty conditions. Provide them with adequate humidity and air flow.

SNAILS AND SLUGS

Symptoms: Snails and slugs live in the crevices of leaves and sheaths and in the root system and come out at night. They chew on tender shoots and growths, leaving stubs, and holes in their place. Also watch out for a shiny trail left behind when they move around.

Treatment: Immediately repot your orchid in fresh medium and discard the old medium.

Before repotting, rinse the orchid roots thoroughly and treat them with 3% hydrogen peroxide. This will kill any snails and also destroy their eggs if any.

Prevention: Isolate the plant when you buy it. Look out for signs of pest infestations. Unpot the orchid at the earliest and repot in fresh media.

APHIDS

Symptoms: Look out for tiny insects that suck the sap by attacking buds flowers and leaves, and leave behind a sticky gel mass. Bud blast and deformed flowers can be attributed to aphid infestation.

Treatment: Try to conservatively remove aphids by spraying water mixed with a few drops of dish wash liquid. For a major infestation, spray an insectide using below recommended proportions.

THRIPS

Symptoms: Thrips are very tiny insects that are not visible to us. They feed on flowers, leaves and buds, and very soon spread from one plant to the other.

Unopened buds drying and falling off, stunted growth and deformities in buds and flowers with damp spots are common signs of thrip infestation. Leaves have a pitted, stipled, silvery or bleached appearance.

 Treatment: On discovery, spray the affected plants and flowers once a week with an insecticide such as as neem oil at concentrations below the recommended dose, and repeat for 3 consecutive weeks. This will help keep these insects at bay.

Prevention: Keep the plants, clean and free of dust and away from trees that are commonly infested with thrips such as trees that produce fruits and flowers.

BIOSDUVAL SCALE

Symptoms: Like spidermites, scale are sap sucking insects that live on the underside of leaves. They are often seen in the axils of leaves, on pseudobulbs and on the rhizome of the infected plant. Old leaves and pseudobulbs that are in dry and dusty environment are especially susceptible to scale.

The female reproduces by laying about 200 eggs, which take 5-6 days to hatch.These are creamish spots that are circular and crusty. A good way to confirm this is to scrape the spot with your finger nail. If it comes off, then it is definitely scale.

Another characteristic symptom is the chlorosis or yellowish halo surrounding these patches. In due course the area darkens and the leaves drop away, causing severe damage to the plant.

 Treatment: If the infection is mild, then use a cotton bud or Q-tip dipped in 1:1 solution of isopropyl alcohol and water. In case the infection is more severe, then spray with below recommended strength solution of a suitable insecticide Neem oil and  dishwash soap solution can also be used in a similar way to get rid of scale. It is important to apply these treatment remedies at a stage when the insects begin crawling as they are at their most vulnerable stage then. For best results, repeat the treatment after two weeks. Ensure that you cover all nooks and crevices under the leaves and axil area.

Prevention: On spotting them, you can scrape off the crusts with a Q-tip. Treating them conservatively with isopropyl alcohol early on will reduce significant damage and spread to other plants.

Keep plants well-groomed by removing dried leaves and sheaths, and regularly check all crevices and underside of leaves for scale infestation. Keep the orchids free of dust, especially in the dry winter climate.

MEALY BUGS

Symptoms: Mealy bugs get their name from the powdery white cottony substance that covers these insects. They attack all parts of the orchid from roots to rhizome to the leaves. They especially make nests in crevices and hard to reach places like leaf axils, inside sheaths and tender new growths and suck the sap in these areas. The surrounding areas show prominent chlorosis, followed by darkening, and subesquently leading to yellowing of the leaf, causing it to drop prematurely.

Treatment: Similar to treating scale, mealy bugs can be cleaned with cotton buds or Q-tips dipped in isopropyl alcohol (spot cleaning is recommended as opposed to wiping entire leaves). For severe infections, spray all plant surfaces such as below the leaves and in the axils with below recommended dilution of an organic insectide. Repeat application after two weeks.

Prevention: Remove old leaves and sheaths to check vulnerable places like leaf axils and underside of leaves. Ensure new additions to your orchid collections do not have mealy bugs. Isolate for two weeks, before placing them with your other plants.

Bacterial and fungal infections

BACTERIAL SOFT AND BROWN ROT (ERWINIA)

Symptoms: First visible signs include moisture filled soft spots with a yellow halo surrounding them. As the infection progresses, the rot progresses rapidly and leaves fall off. The infection can spread to the roots very quickly, finally spreading, albeit much slowly, to the rhizome and pseudobulbs. There is a characteristic foul odor of decaying tissue and a water soaked appearance. Bacteria mostly spread through open wounds.

Phalaenopsis, paphiopedlum and vanda orchids decline rapidly with such infections due to the attack on leaves or crown and stem causing rot issues. They are especially vulnerable since they are monopodial as compared to cattleya, oncidiums and dendrobiums, which have multiple pseudobulbs on a rhizome. So the chances of saving these orchids is greater than those of saving monopodial ones.

Treatment: Unpot your orchid and discard the medium. Remove infected tissue using a sterile cutter and dispose of the infected portions. Wash the healthy portion of the plant. Apply a dilute solution of dishwSh soap and rinse thiroughly. Pat dry with absorbent tissue and spray with 3% hydrogen peroxide. Let stand for 10 minutes on a sterile surface area. Seal the cut portion or exposed tissue with cinnamon powder, which dries up and seals the wounds.

Prevention:  Crown, stem and leaf rot are commonly seen in cases where water and fertilizer get into the crevices and axils of leaves. Avoid splashing water on leaves and pseudobulbs as well as the crown of the plant while watering the orchid. The disease is spread by accumulation of water and bacteria that are present on the plant, which are encouraged by hot and moist conditions. Periodic spraying with a copper bactericide and ensuring there is no water dripping on to the plants will ensure that the orchids remain healthy and free of rot issues.

Bactericides like a copper fungicide can also be used in below the  recommended proportions. Do not repot the orchid immediately. Allow it to remain bare-root for 48 hours. After that, you can repot orchid in fresh medium. Clean up your work surface with 10% bleach to remove any traces of infected material.

BOTRYTIS

Symptoms: Leaves and flowers are commonly affected.There will be a prominent browning and drying up of leaf tips, which progresses towards the base of the leaf.

Flowers develop black or brown spots, which are filled with moisture on the petals and sepals, which merge and grow, marring the beauty of the flowers.

Treatment:  Spray a systemic fungicide such as SAAF with below-recommended dose dilutions to clear up the infection.

Prevention: Good air movement, general cleanliness, higher light and lower temperatures discourage such infections. Remove dried up and wilted flowers as these get easily infected and spread it to other parts of the plant.

Avoid spraying water on leaves and flowers. In case you do, ensure that the excess moisture dries off quickly by placing it under a fan or where it receives air drafts.

FUSARIUM WILT

Symptoms:

If you spot leaves that are yellowish, thin, shrivelled, wrinkled or wilted, you should supect a fusarium infection. This is caused by the blockage of movement of sap through the vascular system of the plant.

When you cut open the rhizome of an infected section of the rhizome, you will find a prominent pinkish purple ring surrounding the rhizome. This is the confirmation of the dreaded fusarium infection. Mildly infected plants can survive up to a year, whereas a severely infected plant may decline rapidly over a period of 3-9 weeks.

Treatment: The first thing you need to do without any delay is to cut away the infected rhizome and discard it. Repot the portion showing healthy tissue without any purple band surrounding it. Clean the healthy portion of the plant and soak in a systemic fungicide such as SAAF as per the manufacturer’s instructions. Sterilize all tools and work area to prevent spread of the disease to other healthy plants.

Prevention:

Fusarium Wilt spreads from one plant to the other through improper sanitation and handling practices. Therefore make it a practice to sterilize your tools and work surface before you repot your orchid.

More importantly, sharing of water is seen as the culprit that can rapidly spread the disease and reduce your collection drastically. When you water your plants, ensure that the water from the drainage holes does not drip over the plants placed at a lower level. This can also spread fusarium.

VIRAL INFECTIONS

Viral infections are mostly spread through insects such as aphids and mites or through infected tools used for tending to your orchids.

Symptoms:

These infections are often characterised by chlorotic and necrotic lesions, indicating the destruction of chlorophyll and rotting of tissue. There may be a characteristic appearance of streaks and rings on leaves. The virus attacks all parts of the plant – stem, leaves, flowers.

Treatment: Viral infections are devoid of any treatment methods due to the difficulty in diagnosis as well as their tendency to mutate. On seeing these symptoms, the best course of action would be to destroy it completely so that it does not spread any further.

Prevention:  Transmission of viral dieasases is inadvertently done when tools such as cutters come in contact with the sap. Therefore sterilization by rubbing with isopropyl alcohol and flaming it properly for 15-20 seconds is an absolutely necessity to protect your other plants.

Prevention is better than cure

As a general rule, introduce best practices in the care routine of your plants to prevent the spread of diseases to your entire collection.

1. Routinely inspect your orchids with a keen eye. Observe for signs of root damage, dehydration and pest infestation.
2. Isolate the diseased orchid and treat it at the earliest so that the infection remained confined to a single orchid and does not spread to other plants.
3. Avoid sharing of water between your orchids. Devise ways to water your orchids individually or at least minimise spread by restricting sharing within a small group of orchids. This way, your entire collection will not get infected.
4. Use sterilized tools such as cutters and pruners for removing diseased portions and tidying up your plants. Always sterilize your work area with 10% bleach before placing your orchid on it.
5. Repot your diseased orchid using fresh media and sterilized pots after treating it. Throw away the old media. Also sterilize stakes, supports, clips, etc. that are used for supporting the orchid.
6. Keep your orchids well-hydrated and fertilize them regularly for a robust growth as their chances of survival dramatically increase if treated in the early stages of onset of disease..
7. Have the necessary treatment remedies such as hydrogen peroxide, rubbing alcohol, cinnamon powder, potassium permanganate, any systemic bactericide and fungicide,  neem oil etc. handy so that your orchid can be treated at the earliest.
8. Stock up on supplies like potting media, pots, stakes and other material to treat and repot your orchid without delay to minimise stress to an already stressed orchid.
9. If there is a risk that your infected orchid can wipe out your entire collection, then it is better to let go of the plant rather than risk downsizing your collection due to rampant spread of the infection/ pest infestation.

You can’t save them all; instead you learn and grow

Every orchid grower faces a few or most of these conditions at some or the other time during their journey as an orchid hobbyist. You will feel bad every time a plant suffers a setback or you lose it, as you have been caring for it like a doting parent for months or even years. Second, these plants are expensive and a replacement is going to cost again. Third, sometimes, these problems reduce your collection significantly, and this can be very disheartening.

But then, you need to take these losses in your stride.

Believe me when I say, for the very best of reasons, what can’t be saved, needs to be let go.

At the end of the day, it is well worth understanding that orchids can be easily sourced and replaced through your local garden centre or nursery or even through online purchases.

With every such setback, you learn and grow, and become adept at problem-solving through exploration, experimentation and DIY hacks. This is what makes this hobby so exciting.

Due to the large number of issues and diseases seen in orchids, I will be extending this discussion  in a subsequent post.

Till then, happy growing!

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