Boston ferns offer plant parents all sorts of uses and benefits and tend to be relatively free of pest and disease problems as long as it is given enough humidity and kept out of the sun. However, the habit that many plant owners have of leaving these ferns outside for the summer can expose them to more pests than they might encounter inside the home. It’s also possible for the fern to suffer from a few diseases, especially if it’s not given the best care. This guide will take you through 9 of the most common Boston Fern pests and diseases and what you can do to mitigate them effectively at home.
Boston Fern Pests & Diseases – Key Takeaways:
The trick to keeping Boston Ferns pest-free is checking the fronds regularly for signs of damage. Few pests can damage the Boston fern, but slugs and snails are a common problem. Diseases that can damage this fern include root rot and multiple types of airborne blight. Try treating the plant with insecticidal soap or horticultural oil, as well as providing optimal plant care to mitigate common problems.
The Most Common Boston Fern Pests and Diseases (& How to Identify Them)
A healthy Boston fern (Nephrolepis exaltata) being kept in the temperature range and humidity level it prefers is likely to experience relatively few issues with pests and disease. If you do experience a problem, it will likely be one of the following issues.
Check the entire plant over at least once a month, separating the fronds down to the soil level, to catch signs of pests and disease while they can still be treated.
1) Nematodes
Nematodes are one of the few plant pests that remain hidden in the soil, damaging your Boston fern where it’s hard to tell anything is going wrong. These pests are tiny worms that are too small to see with the bare eye.
You’ll need a soil test to determine if this is the problem with your plant, which may not be worth the effort for a single ailing houseplant. Most nematodes affecting indoor ferns will cause fronds to become wilted individually, which is not a sign of a lack of watering. New fronds may come out stunted, curled, or turn yellow with a prominent deformed appearance.
Only spraying the soil off of the roots of the fern and repotting your Boston fern in a new batch of soil mix that is not contaminated will help, and it may not save the plant. Where possible, it’s worth inspecting new Boston ferns that show signs of having nematode damage before completing the purchase.
2) Mealybugs
Small, fluffy, and mostly white, Mealybugs are nonetheless hard to spot because of their small size. These sap-sucking insects also tend to hide on the undersides of fronds and at junctions where individual leaves join the rib. You may notice the fern feeling sticky to the touch instead because these pests leave sugary deposits behind known as honeydew. This can lead to black mildew growth on the fern as well. Mealybugs tend to hitch a ride on other houseplants or linger near the soil until they can spread throughout the plant.
3) Fern Mites
A wide range of plant mites only target ferns, including the Boston fern. Often as small as a grain of salt, these mites tend to spread out over the fronds and suck sap from them with tiny spots of damage. This tends to create a general rusted or reddish look to the normally green foliage.
If you notice browning or color changes that aren’t limited to the tips of the fronds, you’re likely dealing with some kind of fern mite. This problem often overwhelms the plant and seriously damages it before you find the signs of the infestation.
Keep your fern as healthy as possible to keep mite levels low naturally rather than planning to fight them if you find them.
4) Aphids
Slightly bigger than mites but still easy to miss, Aphids are drawn to ferns both as a food source and for cover from predators. These insects can travel far despite their size, so any Boston fern that goes outside for the summer is at risk of picking them up.
Aphids can reproduce rapidly and cover a plant with the right indoor conditions to encourage their eggs to hatch. Washing down the plant weekly is already an excellent idea to keep dust off of the foliage, but it can also help knock down Aphid populations and help you spot them before they can multiply.
5) Whiteflies
One of the few flying insects to affect Boston ferns, whiteflies often spread from nearby fruit or shade trees to nest in the foliage. Whiteflies are just as the name describes, a white-colored fly that leaves sticky deposits behind much like the mealybug. This means that you might notice mold growth on the fern’s fronds before noticing any of the actual flies themselves.
Spraying the fern off with a pesticide spray before bringing it indoors for the winter can make sure this pest doesn’t start multiplying inside the house.
6) Snails and Slugs
Boston ferns are highly attractive to snails and slugs, primarily when grown on the ground or in outdoor containers. You find dozens of slimy pests visiting your patio or even climbing columns on your porch seeking out your fern. This is due to their nutritional value for the slugs and also because the humidity trapping fronds help give the pests a place to stay well-moisturized.
You may find dozens of snails or slugs in your Boston fern without even noticing much damage at the end of summer. Make sure to go through and pick them out by hand when bringing a fern indoors, so they don’t reproduce in your fern over the winter.
7) Root Rot
Since this houseplant prefers a steady water supply and moist soil, it can eventually become afflicted by root rot. This is a bacterial or fungal infection that rots the roots that aren’t getting enough airflow or a chance to dry out occasionally.
A container without proper drainage or the use of a humidity tray can encourage this problem. You’ll notice dramatic wilting and a loss of the oldest fronds first. Only drying out the soil mix and using a better draining container will help.
8) Rhizoctonia Aerial Blight
One of the few diseases to affect Boston ferns, this type of blight causes dark brown to tan patches of damaged tissue to spread over the fern’s foliage. Entire fronds may wilt or collapse due to the development of these lesions. It’s most likely to occur when outdoor conditions are very humid and hot, which is hard for this particular fern to handle. You may want to bring Boston ferns indoors at the high of summer to keep blight from becoming a problem for them.
9) Bacterial Blight
Other types of fern blight may be bacterial in origin. These infections tend to cause darker, wetter-looking lesions to form on the fronds. The stems may weaken and darken, breaking off at the soil line. This disease is also triggered mainly through humid conditions and high heat that stresses the plant. Once a plant is badly infected, it’s unlikely to be saved even by drastic measures.
Pesticide and Insecticide Options
Dealing with insects on a Boston fern usually takes a multipronged approach. Due to the density and overlapping arrangement of the foliage, you’ll need to use manual efforts to find and remove as many pests as possible.
Put on a pair of vinyl gloves if you’re uncomfortable handling slugs or squishing mealybugs. Once you’ve checked over the plant and removed any bugs you can find, you may need to add the power of a pesticide or insecticide to the mix.
Horticultural oil is a good choice for ferns because their leaves can handle being coated with the mixture without damage. You can try using a light coating of canola oil for a homemade pest-smothering treatment.
Insecticidal soap will remove stubborn Aphids and mealybugs with only a few repeated applications. Consider using a broad-spectrum insecticide spray that’s listed as appropriate for ferns to kill off any hidden pests when moving a Boston fern in from the outdoors.
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How to Use Pesticides & Insecticides for Boston Ferns
Don’t overuse pesticides on Boston ferns as a preventative measure, even natural and organic options. The fern should primarily resist infestation and disease if it’s strong and growing well.
Spraying the plant down with plain water regularly goes further than trying to constantly target early signs of problems with chemical treatments.
Managing Pests and Diseases
Boston ferns need a higher than average humidity level, preferably around 60% or above. Keep them away from drafts and dry air that may brown the tips. Boston ferns thrive best when exposed to bright, indirect sunlight throughout the majority of the day.
Water regularly and mist at least once a week to keep dust under control. Boston ferns will also benefit from fertilizing in the spring and summer months.
Boston ferns that are outdoors are at greater risk for an attack from pests, so consider treating those specimens once a month or so with a general-purpose insecticide. Putting slug bait out around the plants can stop the damage from those pests in particular.
Wrapping Up
Don’t panic if you see the early signs of pest infestations on your Boston fern. With a trim of the affected fronds and a targeted treatment, you can save your plant and prevent insects from moving in. Avoid diseases by using a well-draining potting mix and bringing the plants inside during periods of extreme humidity and heat.
Andrew is the Editorial Director at Petal Republic. He holds a BSc degree in Plant Sciences and has trained professionally at leading floristry schools in London and Paris. In amongst overseeing a global editorial team, Andrew's a passionate content creator around all things flowers, floral design, gardening, and houseplants.
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