Phyllosticta Leaf Spot: The Cause of the Issue and the Fixes

Phyllosticta leaf spot is an issue on orchids that can happen for many reasons, like fungal infection, pathogen, bacterial infestation, and excessive use of herbicides.

Phyllosticta Leaf Spot

If you need to know which reasons apply to your plant, this guide is for you. Read on as we discuss these reasons in detail and help you resolve the crisis.

Why Does Phyllosticta Leaf Spot Infest Your Orchids?

Phyllosticta leaf spot infests orchids because the plant undergoes fungal and bacterial infections due to the lack of adequate plant care. It could also occur due to different bacterial invasions in the plant and excessive and unnecessary use of herbicides.

– Fungal Infection

The fungi produce black and tiny fruiting bodies within the necrotic tissue and spores that easily circulate to healthy orchid foliage during humid weather conditions. Even though such conditions are ideal for orchid growth, they can increase the intensity of the fungal spots.

The severity of the infection can lead to the removal of the infected. Removing symptomatic leaf tissue from the growing area may help to reduce the disease pressure in wet weather; however, the more the medium is wet, the more they will spread.

The healthy orchid plants are infested by the fungi that emerge from the neighboring infected plant debris in spring and are spread by wind and rain. While the infection methods for the fungus are unknown because they can take place in different ways, a few Phyllosticta species are known to infect leaves via moisture, which makes orchids the perfect candidate as they thrive in humid conditions.

Furthermore, the mature lesions of orchids are home to the fungus that forms pycnidia over winter and repeats the cycle. Common Phyllosticta Leaf Spot symptoms include brown spots, tiny fruiting bodies appearing as black dots as well. On the other hand, you must also note how it can also survive on seeds and infect fresh crops and fields through infected seeds, and most often, this type prefers moist and cool conditions to germinate.

– Bacterial Invasion

Orchids do not show any immediate spot disease symptoms. However, these plants will catch the bacteria that can travel long distances on moist air currents or be moved short distances by splashing rain and irrigation. This is because the water splashing can be a dirty or intoxicated type of water, and how greatly invasive they are.

Moreover, bacteria affect orchids due to frequent rain, warm temperatures, diseased seeds, high relative humidity, and planting materials. It is also caused by over-crowded plants having low sunlight penetration and poor airflow. Furthermore, poor soil nutrients, ineffective irrigation management, and poor drainage promote infestations.

– Frequent Use of Herbicides

Orchids have spot disease on their leaves due to the injuries made by herbicides in contact with the plants. Even a low contact rate with herbicides can result in speckling or spotting of the plant’s foliage. Herbicides can also cause red spots on your orchids shortly after the application if you use it more than what is necessary.

Frequent Use of Herbicides

Phyllosticta leaf spot Japanese maple, Phyllosticta leaf spot of chrysanthemum and Phyllosticta leaf spot magnolia infestation are issues caused by phyllosticta leaf spot orchid infectious disease as well. This is due to the herbicide you may be using, and the excessive amount would damage them all, and it could be contagious too.

How to Cure and Prevent Spot Disease on Orchids?

To cure the orchid leaf spot disease, you must decrease herbicide use and allow your plants sunlight and air circulation. In addition, you can also tackle the bacteria using a fungicidal liquid or spraying some homemade or commercial remedies and tackle them.

– Spray Fungicidal Liquid

You can save your orchids from the pathogen by rotating to non-hosts and using tillage to remove infected residue. As infected seeds can transmit the pathogen, which is why it would be best to do seed testing first. Use fungicides to prevent your orchids from such infestations and spread it well, coating them evenly.

Many broad-spectrum fungicides effectively control the infection’s spread on your orchids. You can also apply copper-based fungicides to prevent the spores from germinating. Gardeners also recommend minimizing leaf wetness and improving air circulation for your orchids in areas where ornamental plants are experiencing.

You can also use commercial gardening remedies to help your orchids revive from the disease. Best of all, use completely non-toxic honey bees and other beneficial pollinators. Another fungicide containing copper and pyrethrins is a one-stop solution to save your orchids from spot disease and other infestations.

Cover the upper and undersides of the orchid for best results with a thin layer of fungicide. Repeat applications every seven to 10 days after a patch test to see how the orchid reacts, as needed. Also, heat water seed treatment can be used because the treatment helps reduce the number of pathogens in the orchid’s seeds. Some industrial vegetable seed companies use this method to eradicate various pathogens. Moreover, you can also use disease-free seeds or resistant orchid cultivators to avoid inconveniences.

Apart from using treatments and various fungicides, removing and properly disposing of the infected part of the orchid side by side saves your plant and your time. Remember to sterilize your tools at the beginning, during, and end of the process so that the orchids are not affected again. Also, avoid working on orchids when they are wet, because this will trigger the pests.

Contrary to popular belief, bactericides such as copper products cannot cure diseased plants but can help prevent the transfer of the infection to healthy plants. You can also use copper-based sprays to control the spot disease, but they are less effective when used alone regularly.

– Tackle the Bacteria with Homemade Remedies

Spraying the orchids with a baking soda solution containing a tablespoon of baking soda, two and a half tablespoons of vegetable oil, a teaspoon of liquid soap, not detergent, and one gallon of water, is effective in controlling the spread of the bacteria. You would make these ones at home, where the chemical used is not strong, but the result is effective.

Tackle the Bacteria with Homemade Remedies

You can also spray some neem oil on your orchids if you wish to avoid it when pollinating insects, including bees or other beneficial pollinators, are present. This is because they may contaminate this disease all over other plants, so to be safe, you can proceed with this process.

Use the solution with the baking soda solution for more effective results. Spray only a few drops of the phyllosticta leaf spot treatment and then thoroughly check for a reaction before applying it every two weeks on the leaves.

– Minimizing the Use of Herbicides

You can spray your orchids with herbicides, but remember, they can lead to other plant issues. It would be best if you buy clean seeds from a reputable source. Also, you can prevent the disease from spreading to other parts of your orchids by not collecting the seeds from the infected plant.

Ensure that you place the infected orchids outside so that they receive good sunlight, sufficient water drainage, and air circulation. All these factors play a huge role in reducing the need for herbicides. Also, avoid over-fertilizing your orchids with nitrogen-rich fertilizers, and maintain a high mowing height.

Avoid irrigating in the pre-dawn or early morning to prevent the orchid leaves from getting wet. Moreover, you could also try to remove and destroy any infected fruits and vines in small gardens at the end of the season to save your orchids from further damage. This way, they will be on a healthier range and a better structure to grow in.


Understanding why your plants have the spot disease is simple now that you have gone through our article and even learned how to solve the issue! Let’s sum up the key points mentioned, so you are fully prepared to help out your plants:

  • Phyllosticta leaf spot scientific name is Phyllosticta Minima.
  • You can avoid the disease by allowing it to take in sunlight and fresh air.
  • Avoid using herbicides frequently because they are toxic to the plant. Opt for home-based remedies instead.
  • Allow the plant to dry before you start working on it. Wet plants are more susceptible to breakage and other diseases.

After reading our recommendations, you can certainly go a long way in caring for your plant and keeping the spot disease at bay!

5/5 - (20 votes)

Leave a Comment