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Share to PinterestLook Out For These Common Orchid Diseases and Pests
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Look Out For These Common Orchid Diseases and Pests

By Alicia Smith
Share to PinterestLook Out For These Common Orchid Diseases and Pests

The graceful orchid is one of the world's most popular ornamental houseplants. Moth orchids are regularly found in big box stores and are relatively easy to look after, but they're just one of the thousands of beautiful species you can find globally.

These flowering plants have long been prized, but they're not immune to diseases and pests. Identifying the problem at hand is a crucial first step and doing so early stands you in good stead for keeping your plant healthy and happy.


Bacterial soft and brown rot

The culprit in this disease is a pathogen with an affinity for warm, moist conditions. You'll notice water-soaked areas often haloed with yellow. The wet rot can spread to the roots, and you might catch an unpleasant whiff.

Phalaenopsis or moth orchids, specifically, can succumb within a few days of infection, so keep a watchful eye. Employ a hydrogen peroxide spray, and you may be able to rescue your orchid and its neighbors.


Black rot

Black rot can be alarming. Dark lesions expand until the foliage looks as though it's been brushed with black paint. Affected areas are soft to the touch and ooze water when pressed. Black rot comes from zoospores in water, so be aware of potential contamination from water sources near your orchid.

Keep your foliage dry as much as possible and treat infected plants ASAP by cutting out affected tissue and applying a paste of cinnamon and cooking oil to the wound.


Southern blight

Share to PinterestOrchid plant with yellow dry leaf
alexytrener / Getty Images

Southern blight is a fungal infestation caused by a hot and excessively humid environment. If your orchid's leaves are yellowing and wilting, southern blight, or collar rot as it's also known, may be to blame.

Look at the stem to check if it's yellow and see if the base of the plant has started going brown and white with fungal growth. You'll need to remove the affected tissue and treat what remains with a fungicide to save the plant. In addition, address the root of the issue by improving air circulation with fans.



Botrytis is also known as orchid blight. Older plants are more likely to develop this fungal problem resulting from a lack of adequate air circulation and damp and cool conditions. You'll notice brown spots on your Phalaenopsis and Cattleya flowers, but the disease can affect other types too.

Remove any infected flowers and spray the rest with a baking soda solution. Like southern blight, botrytis can spread from one plant to the next, so isolate new plants for a few weeks before reintroducing them to a common area.


Leaf miners

Share to Pinterestleaf miner pupa

Various insects such as beetles and moths are leaf miners. These bugs feed on cellulose and create distinct vein-like tunnels through orchid tissue. The larvae live inside the leaves, so they're difficult to treat with pesticides.

Leaf miners cause damage that makes your orchid more susceptible to fungi and bacteria. Get rid of all the infected leaves, and use an insecticide to kill the white grubs.



Share to PinterestParasitic mealybug on leaves of orchids
Stanislav Sablin / Getty Images

Mealybugs are one of the sucking insects to watch out for and address quickly. Newbie plant owners may mistake them for fungi because they look like white cotton balls. Assess the situation. If you see just a few mealybugs, dip a Q-tip in isopropyl alcohol and wipe away the insects.

In cases where large sections of a leaf's underside are covered in these impostors, use a pesticide as per the instructions and reapply it two weeks later for good measure. Ask your local nursery about products you can apply to the soil — the insects will feed on this treated plant and die.



Share to Pinterestred mite on plant in the wild

Mites are not insects — they are a type of arachnid, and they tend to show up in warm, dry, and poorly lit conditions. These tiny critters are brownish-red, and before you notice them underneath the leaves, you might observe the havoc they wreak. Leaves may start to look silver or mottled, and there might be webbing and evidence of mite droppings. The thinner your orchid's leaves, the more vulnerable it is to attack by mites.

Apply neem oil or a store-bought miticide three times over two weeks or as recommended on the package.



Share to PinterestThrip insect
PansLaos / Getty Images

Thrips, like mites, are hard to detect without a magnifying glass. So, again, you'll likely see the damage they cause before you ever clock one of these slender creatures. Blowing into an open flower may stir activity and confirm your suspicions.

Thrips suck on plant sap and cause bud blast. They will wreck your much-anticipated flowers and discolor the petals. Thrips are little travelers, so check surrounding plants as soon as you become aware of them, and treat affected plants with suitable insecticides.


Fungus gnats

Share to Pinterestfungus gnat
Tomasz Klejdysz / Getty Images

Fungus gnats fly around orchids and deposit harmful droppings. These common black insects with greyish wings are harmless to pets and people, but their larvae feed on fungal growth, seedlings, dying tissue, and stray leaves.

Fungus gnats sometimes indicate poor orchid care in the form of overenthusiastic watering and fertilizing. Luckily, the flies and their maggots are a problem easily remedied. Use yellow sticky cards from a garden center to trap the adults, and maintain well-drained soil by repotting your orchids with slow-decaying mixes.



Share to PinterestFemale aphid with new baby nymph

Aphids are soft-bodied insects that can damage your orchid by sucking its sap. They're often less than an eighth of an inch long and are more harmful than their size belies. Aphids can transmit plant viruses, and as a group, they can lead to arrested plant development and death. You may notice a sticky deposit on leaves, which is the honeydew secreted by these bugs.

Getting rid of aphids can be challenging. Start by checking underneath leaves and spraying water forcefully enough to remove them without further damaging your orchid. Then treat the plant with neem oil or insecticidal soap. You may have to do this more than once to eliminate the problem.



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