The beautiful bird of paradise can breathe life into any indoor space or garden with its colorful appeal. That’s why it can be quite disconcerting to see black spots on your Strelitzia plant.
Your initial instinct may be to go into panic mode and throw away your plant thinking it’s doomed, but hold your horses – I’m here to help you identify what may be causing the black spots.
Black spots on your bird of paradise are commonly a result of sooty mold on the leaves and stems. It results from the mold growth on the honeydew excreted by sap-sucking insects. Other potential causes include bacterial/fungal leaf spots, stem & root rot, and overwatering.
You will be surprised to learn that there are effective ways to not only treat but also prevent these black spots from blemishing your bird of paradise in the first place. Read on to get the lowdown.
Contents
What Causes Black Spots on a Bird of Paradise?
Many different potential culprits can cause black spots on your bird of paradise. It’s crucial that you are able to distinguish the primary problem and apply the necessary treatment to save your plant.
With that, here are the most common reasons for your bird of paradise having black spots:
[1] Sooty Molds
Sooty mold is undoubtedly the most common reason for black spots on birds of paradise. You can be relieved because this isn’t a sign or symptom of an actual infection or disease.
When the sooty molds appear, there’s a good chance that your bird of paradise is already playing host to some sap-sucking pests that ooze honeydew, such as aphids, mealybugs, and scale insects. They feed on the sap and release this sticky, sugary substance as excrement.
Sooty mold spores land and stick onto this gooey mess and germinate into powdery fungal growths. That’s what you see as black spots on the leaves or even stems of your bird of paradise. Funnily, ants also do love the sweet honeydew and you may spot them lingering around the plant.
The fungi responsible for the sooty mold don’t actually infect your bird of paradise. However, they look unsightly and may hinder light absorption and photosynthesis.
If there’s too much syrupy substance, a black or gray powdery coating may extend to cover the whole stems or leaf surfaces. You can still find the black spots underneath when you wipe off the coating.
How to Treat
– First, eliminate the root cause: sap-sucking insects.
- Apply an insecticidal soap – While a homemade insecticidal soap can suffice, I prefer to apply a ready-to-use formulation like an Insecticidal Soap
- Spray using horticultural oil – Prepare by mixing 1 gallon of water plus 4 tablespoons of paraffin or neem-based oil to curb aphids (and whiteflies if they’re present). Any horticultural oil will help combat scale insects and mealybugs.
- You can also wipe off the pests using alcohol-soaked cotton swabs.
You should repeat this treatment after every 5-7 days until you eliminate the pest presence. It’s highly unlikely that the sooty mold will flare up again once you have gotten rid of the insects.
– The next step is to control the sooty mold. You should start doing this a day or two after the last insect treatment.
- Use a gentle solution of liquid detergent to spray the sooty mold.
- Prepare by adding a tablespoon of the detergent into 1 gallon of water. Apply generously, especially in areas affected by the sooty mold.
- You should consider spraying your bird of paradise early in the morning. This way, the leaves will have adequate time to dry in the afternoon and late morning sunlight.
- Rinse off your plants after about fifteen minutes using a powerful jet of water. You can repeat this treatment once daily until all the sooty molds are gone.
– As odd as this might sound, ants might actually safeguard pests like scale and mealybugs from their natural predators like ladybugs, beetles, and wasps. A dash of cinnamon powder on the honeydew areas will serve as a great repellent against ants.
– It’s also important that you prune away any leaves that look heavily damaged or dead. In addition to preventing the spread of disease, it’ll ensure your plant directs more energy towards recovery.
[2] Strelitzia Fungal Leaf Spots
The Strelitzia fungal leaf spot, better known as Cercospora leaf spot, is a fungal disease that typically infects an overwatered bird of paradise. It thrives in damp environments, so low light, too much humidity, and overhead irrigation may be to blame, as well.
The leaf spot is commonly caused by the fungus Coleosporium spp. Their spores usually travel via the air and germinate rapidly when they land on wet foliage. They usually start developing first on older leaves and appear as either circular or irregular spots.
These spots can run the color varies from light gray to brown to black, although they can also be yellow. If you don’t take any action, they will expand, coalesce, and mar the entire leaf. Even though these fungal leaf spots may not kill your plant, they can result in leaf wilting, withering, and curling.
In severe cases, the leaves might even fall off. And that should serve as a clear wake-up call that you must do something about it immediately!
Solution
- Of course, you must begin by isolating your plant and trimming away affected leaves. Also, make sure to remove and discard any fallen leaves.
- When it comes to fungal leaf spots, prevention is always better than treatment. But if the fungal infection has already reared its ugly head, use fungicides that contain azoxystrobin or myclobutanil.
- For a natural treatment, neem oil can do a bang-up job. Avoid overhead watering, irrigate early in the day, and improve aeration around your bird of paradise. (Source: University of Florida)
[3] Black Spots on Stem
If you find black, splotchy spots on the stems of your bird of paradise, it’s highly likely that you have exposed it to too much direct sunlight. Perhaps your plant resides on a west-facing window and is being hit hard by the scorching afternoon sun.
These black markings are rarely an indication of a pest infestation or disease activity, though. It just means that your bird of paradise would appreciate protection from the hot sun.
Solution
Once you have established that too much sunlight is causing the black markings on your bird of paradise’s stems, you must relocate it immediately to a less sunny spot. It will do best in a bright, sunny spot but the light itself should be filtered, diffused, or indirect.
If some of the leaves are badly damaged by the sunburn, you should trim them away. Check the soil; if the few inches below the surface are dry, water your bird of paradise thoroughly.
[4] Ants Problem
This is one issue that’s truly laughable if you think about it. Do you remember that sweet, nectary honeydew that I said is responsible for sooty mold on your bird of paradise? Turns out, ants love feeding on the same syrupy stuff, too.
What’s funny is that they know that insects on your plant produce the sweet substance and are therefore willing to go above and beyond to protect them.
As such, they form a symbiotic relationship with scales, mealybugs, aphids, or other suck-sapping insects that have colonized your plant. How so?
The ants provide protection against ladybugs, beetles, lacewings, wasps, and other natural predators of the pests. And, in return, they continue oozing even more of the scrumptious honeydew.
Ants don’t just shove away the predators; they also use plant debris to build shelters for their trusty partner, the mealybugs!
Solution
Use an ants’ bait laced with slow-release control like boric acid. Blend roughly half a cup of peanut butter or sweet jelly and 1.25 teaspoons of boric acid.
Smear on the bait and leave it near your plant. The ants will take the boric acid to their nests, where it will be more effective against the colony.
[5] Insect Infestation
Black streaks on the foliage and stems of your bird of paradise are one of the symptoms of pest infestation. Keep an eye out for one or more of the four major sap-sucking insects, namely mealybugs, aphids, whiteflies, or scale insects.
Mealybugs – These are the most common culprits that take a foothold of your bird of paradise. They suck the sap out of the leaves and secrete honeydew that attracts both fungus mats and ants. They’re segmented, flat-looking bugs with a white powdery wax coating.
Aphids – The pests usually form feeding colonies and they come in many colors, including black, brown, red, green, or yellow.
Scales – These sap-sucking insects sport a black or brown body that has no legs or head. The most common are nigra and dome-shaped scale insects.
Whiteflies – Adult whiteflies are easy to spot on your bird of paradise. They are winged and swarm when you shake or disturb your plant. Watch out for white, yellow, or orange larvae on the underside of the leaves.
Although most of these pests may escape your attention, the presence of ants and sooty mold are some of the telling symptoms. If you scrape the powdery mold coating, you’ll see some black spots.
Solution
I’ve already detailed above how to control sap-sucking insects on your bird of paradise. You can use cotton swabs laced with rubbing alcohol, spray with horticultural oil (such as neem oil) or apply insecticidal soap.
[6] Stem Rot and Root Rot
A bird of paradise cannot withstand constantly wet or soggy soil. This will lead to root rot, which is usually caused by the common water fungus Pythium spp. Apart from black spots, other symptoms include rapid leaf yellowing, brown leaf tips, wilting, and drooping.
You should also look out for Armillaria root rot. It’s another fungal disease whose symptoms include stunted growth, stem cankers, and small leaves speckled with brown or black spots. Below the surface, you’ll find brown rusty flaccid roots that feel soft and mushy to the touch.
The same is true of overly damp stems – especially when you water your bird of paradise from above. Under these wet conditions, the soil-borne fungus Phytophthora spp will cause stem roots.
If you inspect your Strelitzia carefully, you will see that the stem has black streaks that advance down towards the roots.
Solution
- If you think your bird of paradise has been affected by stem or root rot, make sure to isolate it immediately. Move it to a warm, less humid area where the pathogen spread will slow down.
- Trim off all infected stems, petioles, flowers, and leaves using a sterilized cutting tool.
- Unpot your bird of paradise and assess the extent of the root rot damage. If some of the roots are still healthy, prune and discard the affected ones. Use a copper-based fungicide and hydrogen peroxide to treat the remaining roots.
- Repot your bird of paradise using a new pot and fresh potting mix. I highly recommend this natural hand-blended mix.
- If all of the roots are rotten or damaged, you’re really in a tight spot. Your last resort might just be to propagate your bird of paradise.
[7] Bacterial Leaf Spot Disease
Bacterial leaf spot is a disease caused by Pseudomonas spp bacteria. Early signs include red streaks and yellow flecks on the leaf undersides. If left untreated, they will turn into larger black spots surrounded by yellow rings. The stems also shrivel up and turn black because of cankers.
Solution
It’s hard to save your bird of paradise once the bacterial leaf spots have turned into a fully-fledged disease. You should avoid wetting the leaves and overwatering your plant.
[8] Overwatering
Giving your bird of paradise too much water is a no-no unless you’re planning to kill it. This water problem will not only drown the roots, but waterlogged soil is also a breeding ground for root rot disease.
Since your Strelitzia is unable to absorb enough water and nutrients, it will start losing chlorophyll. Lack of nutrients and weakened photosynthesis causes the leaves to turn yellow. It won’t take long before black spots appear.
Besides, an overwatered bird of paradise is susceptible to pests, diseases, and other ills that lead to black blemishes on the leaves and stems.
Solutions
If the overwatering is mild, move your plant to a brighter spot to encourage the soil to start drying out. If root rot is present, use the method I explained above to treat your plant.
How to Prevent Black spots on Bird of Paradise
- Make sure to bring home only healthy houseplants. A good way is to ensure the roots are firm, full, and healthy. This is a good disease-protection strategy for your houseplant collection.
- Inspect your bird of paradise frequently for pests and control them as soon as they show up.
- Avoid overwatering your plant. For best results, water early in the morning and don’t splash water on the leaves. Likewise, you should make a point of avoiding overhead irrigation when possible.
- Keep your plant healthy – maintain day temperatures at and night temp of 65-70 °F (18-21°C); place in bright, indirect light, and fertilize weekly in summer & biweekly in spring
- Maintain a high level of sanitation when handling your plants – remove dead plant matter often, sterilize tools, and wash your hands before you handle them