10 Common Bird’s Nest Fern Pests and Diseases (and How to Deal With Them)

Common indoor bird’s nest fern (Asplenium nidus) pests include scale, spider mites, foliar nematodes, shore flies, fungus gnats, and mealybugs. In my experience, pest control can be treated with horticultural oils, such as neem oil or insecticidal soap. Bird’s nest ferns may also be susceptible to bacterial blight, which is best avoided by not getting water on the foliage. Read on to learn what you need to know about common bird’s nest fern pests and diseases.

Common Bird's Nest Fern Pests and Diseases (and How to Deal With Them)

Scale

Scale pests on green leaved plant

Scale is one of the most common pests to afflict bird’s nest ferns. These tiny insects have rigid bodies covered with a gray or tan shell. Since they don’t move very much, scale insects on ferns are often mistaken for spores. Scale insects settle down on foliage and suck the moisture out of the foliage.

They excrete a sticky substance known as honeydew that gives the foliage a shiny appearance. Over time, the foliage grows deformed and discolored, and plant growth is stunted.

Mites

Mites on green plant leaves

Mites are drawn to dusty, dry conditions. Underwatered houseplants are especially susceptible to this pest. Spider mites are the most common; these arachnids are tiny and hard to see. 

Look on the underside of leaves to see the light specks left behind from their feeding, known as stippling, and their thin webs. This pest causes leaves to dry up and drop.

Foliar Nematodes

Foliar Nematodes causing green leaves of a plant to wilt and decay

Foliar nematodes are microscopic worms that infest plant foliage. Though the damage is primarily cosmetic, they can cause leaves to curl and discolor. Severe infestations may lead to browning tips, drying, and dropping leaves.

Shore Flies

Shore Flies on a green leaf

Shore flies start their lives as eggs in moist soil; often, they’re introduced into your house when you bring plants home from the nursery. Adult flies only cause cosmetic damage — a slight stippling on foliage — but are irritating to have in the house.

Fungus Gnats

Fungus Gnats caught in yellow sticky traps placed in a plant pot

Fungus gnats are a common pest in greenhouses. Females lay eggs in moist soil, then larvae hatch and feast on plant roots. Adults emerge after a few weeks and fly around the house, annoying everyone inside. Feeding larvae can stunt plant growth.

Mealybugs

White Mealybugs crawling across the green leaves of a houseplant

These small oval insects swarm along foliage veins and where leaves meet stems, sucking out plant juices. They leave a waxy, powdery substance behind that can attract ants. Mealybugs stunt plant growth and cause leaves to yellow and wilt.

Aphids

Small green Aphids on green plant leaves

Aphids come in various colors, from bright green to brown and black. But these tiny insects all cause damage when they feed on plants. Distorted and curled foliage and stunted plant growth are signs of an aphid infestation. Check underneath foliage where these little bugs hide.

White Flies

Tiny White Flies on the surface of a green leaf

White flies look a lot like gnats, but they’re pale in color, as their name suggests. Adult white flies feed on plant leaves, causing foliage to fade to pale yellow or even white.

Blight

Blight causing discoloration and decay of a houseplant leaf

Bacterial or fungal pathogens cause blight. These microbes attack plants’ vascular systems, leading to necrosis or tissue death. 

When a large area of a plant is affected, it’s known as blight. Blight can severely weaken or even kill indoor plants if left untreated. There are a few different types of blight, including:

  • Southern blight: A fungal disease common in tropical plants, southern blight affects more than 500 species of commonly grown plants in the U.S., including trees, shrubs, perennials, vegetables, and other ornamental plants. Symptoms start as spotting on lower stems, then lead to yellow, wilted foliage, root rot, white fungal threads, sclerotic or seed-sized bumps on plant surfaces.
  • Botrytis blight: Also known as gray mold, botrytis blight starts out as dusty-looking patches of tan or gray on plant foliage. Though it usually affects old plant tissue first, over time, it can spread. Botrytis blight thrives in wet, cool, dark conditions.
  • Bacterial leaf spot: Localized bacterial infections may lead to blight. Exposure to bacteria such as Pseudomonas and Xanthomonas can cause dark green spots that make foliage look soaked. These spots then turn tan, brown, or black with yellow margins and, over time, can affect foliage and stems.

Powdery Mildew

Powdery Mildew patches on a the leaf of a green plant

Powdery mildew is a common plant disease that strikes in warm, dry conditions. It’s caused by a fungus and can affect almost any type of plant. Symptoms include areas of white or gray, powder-like growth. Tiny bodies appear on the foliage, first white, then yellowish-brown, eventually turning black. Infected foliage grows distorted, then yellows and drops.


Pesticide and Insecticide Options/Solutions

A bottle of neem oil next to a bowl of green leaves

Horticultural Oils

Horticultural oils work by suffocating pests with soft bodies, such as aphids, mealybugs, mites, and white flies. These types of insects breathe through tiny holes in their bodies. The oil must directly coat the insects and block their breathing holes to work. Some oils may also disrupt the breeding and egg-laying cycle.

Most oils are petroleum-based, but a few options, such as canola oil, are plant-based. Neem oil (via Amazon), for example, can be used to kill nematodes. This oil is made from the seeds of the neem tree, which contain a naturally occurring pesticide.

Insecticidal Soap

Insecticidal soap can kill several pests, including scale, mites, aphids, and mealybugs. It’s made from potassium salts and, like oils, kills by suffocating soft-bodied pests.

You can also use insecticidal soap to rid foliage of powdery mildew, honeydew, and other contaminants. Dish soap can be used as a substitute in a pinch, but it’s not as effective.

Pesticides

If non-synthetic methods aren’t working, you can turn to pesticides to kill pests. There are several classes of pesticides, all of which can cause damage to humans and animals if misused. Types of pesticides include carbamates, organophosphate, and pyrethroids.

Each type has different application methods and targets other species. It’s crucial to follow the directions carefully, as misuse can cause harm and increase pest resistance.


How to Use Pesticides & Insecticides for Bird’s Nest Ferns

A healthy and vibrant bird's nest fern plant in a clay plant pot

As a general rule, start with the least invasive treatment method. In most cases, you can rid your bird’s nest fern of pests using horticultural oils or insecticidal soap before turning to harsher chemicals.

When selecting a treatment, choose an option that targets the specific pest or disease. It’s important to note any other animals that may be affected and follow the product instructions accordingly. For instance, you may need to apply products at a specific time of day, within a temperature range, or using a particular method.

Give the treatment time to work. While instant results would be great, most pesticides don’t work immediately. Give the treatment a few hours or days before you reapply.


Managing Pests & Diseases

A large, potted bird's nest fern in a white ceramic plant pot

Certain growing conditions exacerbate some pests and diseases. For instance, spider mites and powdery mildew love dry, warm conditions. It’s worth taking extra care with young, freshly propagated bird’s nest ferns as well.

Providing your bird’s nest fern with the optimal environment is your first line of defense against pests, diseases, and other problems. Start with the suitable soil.

Bird’s nest ferns thrive in rich, consistently moist soil that is well-draining but not wet. Provide water when the top inch of soil feels dry, and never water directly into the plant’s “rosette” center, as this may lead to water retention and root rot. Aim for a pH of 5 to 6.5.

Next, ensure your fern has the right amount of light: a medium indirect exposure is best. Place your plant in front of a north-facing window, near an east-facing window, or in a window with a sheer curtain. Keep your plant in a room that’s between 70 and 80 degrees F (never below 60 degrees).

Finally, feed your plant correctly. Provide water-soluble 20-10-20 fertilizer, diluted to half strength, once per month. Feed only during the growing season (spring and summer). Your fern doesn’t need fertilizer during the rest of the year.

Additionally, it’s worth pruning your bird’s nest fern periodically to remove past-prime fronds, and encourage healthy new growth. Additionally, consider repotting bird’s nest ferns in a fresh new soil mix every two years or so.


Wrapping Up

Bird’s nest ferns aren’t particularly susceptible to problems. However, they can succumb to certain pests and diseases. Providing the right growing conditions is your best defense against common issues, such as scale and spider mites. If you do encounter problems, try the least invasive treatment method first.

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