Black Tip fungus is one of the most common diseases for both small plumeria and mature plumeria. The black mold produced by this fungal disease rarely kills plants but can be fatal for plumeria cuttings.
In this article I want to explore some of the best ways to ensure your pants don’t suffer at the hands of this fungus, using some simple growth tricks like proper winter storage, avoiding high humidity and shady areas, and giving your plumeria enough sunlight.
What is Black Tip Fungus?
Blacktip fungus is a fungal infection on the growing tips of plumeria shoots and buds. It occurs most frequently in cold or humid temperatures and in summer when ants crawl up plumeria stems to feed on common plumeria pests.
When this happens, they store the liquid sap, called honeydew, produced by the pests in holes that they dig in the stems. This increases humidity, and in turn, causes fungal infection.
The fungus can be easily treated but spreads very quickly once it is established, so depending on how bad it is, you might need to do some pretty harsh pruning to get around the problem.
What Causes Black Tip Fungus?
The most common cause of blacktip fungus in plumeria grown in the greenhouse is ants. Ants are attracted to the sweet honeydew produced by common plumeria pests and gather the liquid honeydew to store it in holes they make on the tips of plumeria buds, stalks, and stems. The moisture in these holes leads to intense humidity that is a perfect breeding site for fungus and stem rot.
The other insects, like gnats, thrips, and mealy bugs, which produce the honeydew are attracted by the delicious sap from the plumeria itself. The sap is increased by overwatering plant roots as cellulose in the plant leaves is plumped, providing an abundant food source for plumeria pests.
Plumeria pests that lead to blacktip fungus
Thrips, leafhopper, mealybugs, and other sap-sucking insects are the most common honeydew-producing pests on plumeria and can be treated easily with organic pesticides, or hand removal is the best way to prevent infected plants. These sap-sucking insects like thrips damage the plant’s growth which leads to these blacked tips and stem rot.
The best conditions for blacktip fungal diseases to develop are cold, humid temperatures. These are mostly caused by overwatering plant roots or poor plant locations. If you grow your plumeria indoors, simply move the pot to a brighter location, but keep it out of direct sunlight as this can cause other problems like spider mites.
To avoid overwatering plant roots, make sure your plumeria is in a well-drained pot with adequate drainage holes.
How to Identify Black Tip Fungus on a Plumeria Plant
The first sign of this plumeria problem is that blacktip fungus is most noticeable on plumeria tips and fresh buds, where new growth will have a blackened end, usually shriveled and beginning to curl. This is caused by a build-up of humidity that allows the fungal infection to grow.
Black spots on plumeria foliage, stalks, and midribs typically start on and branch tips before new plumeria leaves or flowers form.
If you see blacktip fungus on plumeria foliage, immediate pruning is required, and the affected plumeria leaves should be disposed of in a trash bag, and never added to compost. Fungus thrives in wet compost heaps and will only infect future plants.
Blacktip fungus usually happens in the spring and fall, when humidity is highest. If it happens in spring, plumeria will usually recover by themselves as the fungus is killed off by drier summer conditions. The plant will most likely self-prune the affected areas and send up new growth from below the dropped buds and stems.
Other problems that are mistaken for blacktip fungus
Low nitrogen or phosphorus
Inadequate fertilization can cause black spots on leaves which is often misdiagnosed as blacktip fungus. If you are unsure try adding nitrogen-rich fertilizers or phosphorus-containing additives to the plumeria’s water.
After a few weeks, you should notice some improvement. This is also advised after treatment for blacktip fungus anyway, as it helps your plants grow healthier roots and put more energy into new leaf production, which will in turn aid the recovery of affected parts of the plant.
Sudden changes in temperature
Plumeria is a tropical plant and makes great garden shrubs, but infected plants will drop their leaves and buds as soon as temperatures drop below 50F, particularly important in early spring when the low spring temperatures can have big effects even on mature trees.
This is often mistaken for blacktip fungus as the tips tend to darken when this happens. Don’t worry, the infected plant will recover when the temperatures rise again.
Frangipani rust, Sooty mold, and Rust fungus
Rust fungus and frangipani mold are very similar to blacktip fungus, but with orange pustules and yellow spots that are slower to spread and tend to be located around the midrib of plumeria leaves.
Plumeria rust is caused by spider mites, and the symptoms are easily treated with rubbing alcohol. Fungicides can help, but neem oil is a great treatment here as it removes the spider mite problem, as well as treating the fungus before it develops.
Sooty mold on plumeria is slightly different from blacktip fungus, as it is caused directly by a build-up of honeydew on plumeria leaves and midribs rather than in buds and new plumeria tips.
While it is a mold rather than fungus it can still be treated with fungicides, but like frangipani rust and rust fungus, it is best treated with a dual purpose organic pesticide like neem oil, which will eradicate the pests as well as the mold.
How Black Tip Fungus Affects Plumeria Plants
If left untreated, blacktip fungus will weaken plumerias to the point of complete rot. But it is easy to spot, and easy to treat if you catch it early.
The main side effect of blacktip fungus is that it will stop plumeria flowering. As the ants are attracted to pests on buds and tips, they can cause new buds to rot and fall from the pant entirely, meaning your plumeria will fail to flower if the blacktip fungus is spread across the entire tree.
While this is unfortunate, it isn’t a disaster, as if you catch it early enough, plumeria is quick to recover and can flower again the same year if you catch the funs early enough.
Blacktip fungus can, if left untreated, reach leaves and leaf petioles, which causes the leaves to drop. Again, when this happens, moving the pant to a sunnier location can naturally eradicate the fungus, which is killed in higher temperatures, just make sure to remove the fallen leaves as they can cause the fungus to recur, and lead to other infections later down the line.
How to Get Rid of Black Tip Fungus
Black fungus causes black fungal infections which form on the tips of plumeria leaves, and if left uncontrolled will spread to cover the infected plant and eventually contaminate the entire stem of the plant leading to stem rot, and eventually root rot. If it gets this far, it needs drastic action as the blacktip fungus has infected the main plumeria stem.
The best thing to do here is to prune any affected leaves or affected branches and begin treating the pest problem to prevent any recurring problems.
During the infection, spray the plumeria plant with fungicides every other day. Treat the soil with a fungicidal spray as well as the tips and leaves, to ensure the fungus doesn’t remain present and reappear after treatment has finished.
When you prune your plumeria, prune to healthy wood. The fungus can travel inside the stem and affect plumeria below the visible fungal problem. Cut with clean secateurs until you find healthy wood with white sap.
The clean white sap will quickly heal the cut and prevent further infection, and cutting to just above a bud will allow the plant to regrow from that point and bush out further.
To reduce the appearance of the fungus after treatment, you can spray liquid seaweed on new branches, which will help revive the look of the plant once the fungus has been beaten. The sprays won’t harm the plant and can often mean that even badly affected parts of the plumeria can be kept without pruning, as long as you catch the problem early.
After 2-3 weeks of treatment, repot the plant with better drainage, and place it in a brighter location, watering only once every 2-3 weeks to prevent over-humidifying.
Tips to Prevent Black Tip Fungus
If you don’t yet have black tip fungus but are worried about the possibility, there are five easy tips for preventing plumeria problems.
Black tip fungus hates the heat
First, start by moving the plants to a warmer location, in part shade but with good light levels. The increased temperature will limit the appearance of black tip fungus, which requires dark humidity to grow. For plumeria cuttings, particularly in their first winter or growing season, keep temperatures warm.
Black tip fungus likes wet conditions
Secondly, reduce watering to once every 2-3 weeks, only watering when the top inch of soil is dry to the touch, and never water in winter to maintain low humidity. Watering in winter when the plant is dormant will lead to black tip fungus as there is nowhere for the water to go.
Another way to avoid over-watering is to only water during the day, as watering at night leaves water lying around before the sun comes up and the plumeria springs back into action, so the occasional water shortage might actually help your plant.
Remove pests to prevent black tip fungus
Third, and probably most importantly, remove pests with rubbing alcohol or organic insecticidal soaps. Most cases of black tip fungus are caused by pests, which attract ants, causing humidity in the plant tips. By removing the pests, you remove the opportunity fungus to grow.
Re-pot plumeria plants for better health
Fourth, is to re-pot your plumeria plant into a pot with better drainage. It might seem obvious, but it’s crucial. Good drainage is essential for healthy plumerias. It allows watering to be kept regular and reduces the risk of waterlogging.
Keep pots clean and tidy to prevent black tip fungus
Keep a clean home. Fungal diseases occur most readily when leaf litter is allowed to lay around on the soil beneath plants, as they degrade they increased humidity and can grow molds and funguses that can be transported easily up plants, speeding up a fungal infection.
Though this is not the leading cause, it can promote symptoms to develop faster.
Recommended Products for Treating Black Tip Fungus on Plumeria
Essentially, when applied to fungus and bacteria directly with a cotton swab dipped in the liqud, it breaks down the fungus proteins and DNA structures so they can’t duplicate.
Insecticidal soaps are a great preventative measure as well as a cure. Most organic pesticides will remove molds, fungal spores, and cold winter morning dew deposits from the pests they treat, which will not only prevent black tip fungus but help treat existing infections.
Neem oil is a fantastic option for treating pest problems and fungus at the same time.
Baking soda, as long as you wash it off your plants, is a very effective fungicide, as it dehydrates the fungus. Use it sparingly and spot spray baking soda for an effective ad fast control of black tip fungus, but be careful not to overuse it as it can dehydrate plumeria if sprayed over the entire plant.
Similar effects can be achieved by homemade cloves, garlic, or ginger sprays, which increase the acidy levels to stop the reproduction of the fungus.
Mixing a drop of dish soap into either baking soda sprays or garlic, ginger, and clove sprays will help them stick to the affected area of the plant, drying it out and killing the fungus in no time.
Captan or Bayleton are safer choices for wildlife as they have very little evidence of harmful impacts on insects or mammals, but there are some that should definitely be avoided.
Benomyl, found in most commercial sprays is harmful to insects, so if you want to treat the fungal infection without impacting wildlife, steer clear of sprays that include benomyl.
Avoid oxycarboxin. It is harmful to humans, and pets, as well as beneficial insects, and is sold a general insecticide and fungicide.
Oxycarboxin’s effects on plants are also negative as it can dry them out and prevent their mitochondrial respiration, which is a crucial part of photosynthesis.
Under no circumstances should you use oxycarboxin.
This fungal infection is usually the result of pest infestations and is better treated through prevention rather than cure.
ensuring your plumeria has adequate sunlight, and low humidity is the best way to prevent black tip fungus on plumeria, so if you do find your plants falling victim to the disease, make sure to tackle them naturally, but most importantly, quickly.