Top 5 Causes of Black Spots on Basil Leaves [Learn The Remedies]

black spots on basil leaves

Black spots on basil leaves can be caused by fungus, bacteria and other pests or simply by too much sun exposure. Understand the other signs of basil plant disease to identify the underlying issue.

Basil leaves with black spots don’t look appetizing and in some cases, you really shouldn’t consume them. But before you throw away your basil plant, why not find out what is causing the problem, first? You never know, you might be able to salvage it.

These are the most common causes of black spots on basil plants and what to do about them.

Why Is My Basil Plant Getting Black Spots?

Black spots alone won’t tell you what is happening to your basil plant. Learn how to identify these common basil plant diseases to get to the root cause of the black spots.

  1. Leaf Spot / Cercosphora

Cercosphora is a fungal infection that can affect many different plants. Plants that tend to grow in warm and humid environments are more prone to them which is exactly the climate that basil plants prefer.

How to Recognize Cercosphora

Large black spots with a yellow outer circle and in later stages a white mark in the middle of the circle. As the plant deteriorates, the black marks can become holes in the leaves.

  1. Downy Mildew

Downy mildew is one of the most common plant diseases as it spreads rapidly between plants and is hard to stop. The disease is caused by a parasite that often looks for plants with damaged fruit, leaves or flowers.

How to Recognize Downy Mildew

Black spots with greyish-white fuzz mainly on the underside of leaves. As the disease progresses it can spread all over the plant and nearby plants.

  1. Pseudomonas Chicorii

This is another high humidity loving pest but it actually a bacteria, not fungus. Basil plants are more prone to this disease when the soil is overly saturated with nitrogen.

How to Recognize Pseudomonas Chicorii

Large uneven black spots that eventually become holes. Can be limited to just a few leaves.

  1. Cold Damage

Basil is a warm weather plant and they are quite sensitive to cold temperatures. That is why it is so important to only plant them outdoors several weeks after the last frost.

How to Recognize Cold Damage

Younger leaves are more sensitive to temperature changes so if the black spots are limited to the top leaves (the newest leaves) it might only be a weather problem.

  1. Other Pests

Small plant-eating insects such as aphids and thrips can do serious damage. However, black spots are often a later sign of their presence and so it is important you look out for other symptoms.

How to Recognize Insects on Basil Plants

This will depend on the type of insect. In general, if something is moving around on the plant or causing discoloration, there is something living on it.

How Do You Get Rid of Black Spots on Basil Leaves?

After figuring out the real reason behind the black spots on your basil plant, you can start to solve the problem. If you’re lucky, you spotted the problem in time and you can nurse the basil plant back to health.

Here are a few tips for preventing and getting rid of black spots on basil.

  1. Monitor the Climate

Warmth and moist soil are essential for basil plants but don’t overdo it. Make sure that the plant is not overwatered and avoid leaving the leaves wet. This could create an environment that many pests thrive in.

Equally important, don’t leave the basil plant in a room where the temperatures drop a lot at night and don’t transplant it to the garden too early in the season. This will help to prevent cold damage.

  1. Isolate Plants

Whenever you are bringing in a new plant, there is a risk of introducing certain fungi, bacteria and other pests. That is why all new plants should be isolated for at least 2 weeks.

If you notice a disease on your basil plant, keep it separated from other herbs, too. Don’t bring it back to its place until you are sure you got rid of the infection.

  1. Trim Off the Affected Leaves

If you monitor your basil plant, you are more likely to spot issues early on. Stop the infection dead in its tracks and trim off the infected leaves.

Do this with clean tools and sterilize them right after use. This helps to prevent further spreading to other plants.

  1. Wipe Down the Basil

Yes, many plant diseases like humidity which is why basil leaves shouldn’t be kept wet. But after an infection, it is best to wash off any remaining pathogens.

You can hose down the basil or you can wipe down each individual leaf with a wet cloth. Just make sure that you are not spreading the infection when doing so.

  1. Use Natural Pesticides

Since most people keep basil to use in cooking, you have to be very careful with the use of pesticides. Most chemical pesticides would make the basil unsafe to eat.

A safer choice is neem oil. This is one of the miracle cures that can treat a wide variety of pests without damaging the plant.

how to grow basil indoors

Frequently Asked Questions:

Is Black Spots on Basil Bad?

Black spots on basil are a sign of plant disease so they are not a good sign. Find out what is causing the black spots so that you can decide on a suitable treatment plan.

Can You Still Eat Basil with Black Spots?

Do not eat basil that has black spots. It can be a sign of bacterial or fungal infection and can also be a sign of a pest invasion. None of these things are safe for consumption.

Can You Eat Basil with White Spots?

First find out why your basil has white spots before you decide to eat it. If it is simply due to a nutrient deficiency, it might be safe to eat but thoroughly wash the leaves and cook them before consuming. Always avoid eating it if you are unsure.

Summary

Nobody is happy to see black spots on their basil plants but it is not always a reason to panic. If you can identify the underlying cause, you can often still find a way to save the plant.

Learn to recognize the signs of bacterial infections, fungal infections and pests on basil plants. This will help you to recognize a potential issue earlier on and stop it from affecting the entire plant.

Keeping basil in the right environment and trimming off infected leaves is often already enough. Black spots don’t always mean the end!

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