Black spots on Mint Leaves (Causes & How to fix them?)

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Are you observing some black spots on mint leaves of your plant? The black spots on Mint Leaves can be alarming as the mint might be infected or some other conditions are the reason. So let us know what to do when you spot black spots on Mint Leaves.

Mint is the plant that adds such a cool flavour to dishes and drinks. Most of the gardens have it. The summer days never go without taking out the mint leaves and eating them to feel refreshed. But the plot twists! Black-brown spots appeared! This can be alarming as the mint might be infected or some other conditions are the reason. There can be various causes that the mint leaves are getting blackish-coloured spots which sometimes look brown-coloured as well. 

What are the causes behind the black spots on mint leaves?

Mint rust

Many times when the mint leaves start to have brown spots, it comes out they have mint rust. Mint rust is a fungal infection caused by Puccinia menthae, which is mostly seen in mint plants during the onset of the summer season or the end of springtime. The mint leaves have a powdery layer at the back and start with the powdery spots which are very small in size, in a shade of orange or yellow color. The plant starts to look weird with brown spots. 

Symptoms

  • Start with yellow dusty spots and with turn black colored.
  • The plant looks dull and spots appear on the shoot portion as well.
  • Shedding of leaves occurs with time as the plant gets super weak.
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How to treat

  • Keep the plant clean
  • Don’t let the leaves stay wet for long. Though you shouldn’t wet the mint leaves that much.
  • The old dead parts should be removed from plants as well as soil which can lead to fungal growth
  • If the spots have just started, you need to dig the plant up, give heat treatment at 111 degrees Fahrenheit for 10-11 minutes to kill the attacks, and then transfer to the cold water for a similar time duration and then replant it. If the plant is too infected it is better to destroy the plant or dump them away from the garden as it can harm other plants too. 
  • Use the clean, sterilized tools for gardening purposes
  • You can use fungicides to kill fungi that have azoxystrobin, tebuconazole, and myclobutanil in them.

Mint leaf blight

Mint leaf blight is actual mint rust more harshly. The mint leaf blight caused by fungus leads to the black spots on the mint leaves. The fungus Cephalosporium leads to mint leaf blight in the mint plants. The moist conditions and water splashes lead to this disease. The mint mostly gets this issue during the winter or spring season when it is too rainy or humid. The disease can be transferred to other mint plants through cutting or close contact with healthy ones

Symptoms

  • The leaves and as well stems get affected.
  • The lower leaves are seen affected by the odd-shaped black spots.
  • The parts get weak and also fall off.

Treatment

  • The diseased mint rhizomes need to be removed or destroyed.
  • Dont wet the leaves for a long time. Keep leaves dry.
  • The overhead watering should be avoided
  • Again give them heat treatment, you can also use specialized chemicals designed to get rid of mint leaf blight.
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Verticillium wilt

The verticillium wilt is caused by the fungus that lives in soil and is named verticillium dahlia. This fungus also leads to black spots on mint leaves. They spread through spores and get active in the wet conditions of spring and summertime. The roots are the first target as the fungus is soil-borne and then the lower leaves get affected. 

To know more about the plant world, you may also read related articles, Aphids on Mint – 7+ Tested ways to get rid of them & prevent them 

Symptoms

  • As the name indicates, wilting of plants is a common symptom where the plant doesn’t get enough water as the root system is damaged.
  • The growth gets stunted, and spots start to be visible on the stem also
  • The leaves curl and twist and they drop from the plant prematurely. 

Treatment

  • Use sanitized tools and sterilized growing medium
  • Don’t let weeds grow, remove them as quickly as possible
  • Give the plant warm dry conditions, and cut the affected parts if the infection has just started.

Anthracnose

This disease also causes black spots on the leaves of the mint plant. The lower side of leaves is usually affected. In rare cases, the new parts are also seen affected. The difference is that the black spots expand with time and lead to the blackening of the whole leaf. 

Symptoms

  • Leaves twist, black spots on stems, and leaves occur
  • Whole leaves turn black
  • Stunted growth of plant’

Treatment

  • Prune the diseased parts of the plants.
  • Avoid overhead irrigation.
  • Mulch the soil and sanitize the tools.
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Pests

Aphids

The black spots are caused by aphids that might cause fungal disease-causing such a situation. The aphids like peach aphids are the main agents for causing black spots. The plants get stunted, with dusty spots on leaves. Just remove the diseased parts from the plants, and clean the leaves with insecticidal soap or neem oil. 

Cutworms

The cutworms harm the plants by cutting them at the base, making them weak with dead spots on the leaves. Use insecticide spray, pick the cutworms and throw them far away.

Thrips

Thrips attack also can cause back spots on the leaves of mint plants. The leaves might die due to full infection. Leaves drop after some time. Wash them with a strong water jet, use sticky traps to collect them, and use insecticidal sprays.

Is it safe to have mint leaves that have turned black?

It is better that you avoid eating the mint leaves with the black spots. The black color on the green leaves is an indication of something unhealthy. The feeling of eating such black mint leaves is also not good. Eating healthy green leaves is always a better and healthy option. 

Summing up the context:

The mint leaves are yummy and have healthy ingredients in the food. We understand how it feels if mint leaves are showing brown colors and fewer green leaves. Though we have uploaded the main causes that lead to black spots on the leaves, there are some other causes like too much sunlight, not enough sunlight, overwatering, underwatering, rootbound mint plants, and too much fertilizer that also cause such issues. We hope you helped you out with your worry and made your mint plant healthy. Happy planting and minting! 

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