Brown spots on basil leaves, when found, are an indication that your care regimen needs to change. Brown spots on basil leaves are often caused by temperature changes, frost damage, nutritional deficiencies, sunburn, pest infestation, or fungal infections.
It takes some observation to reach the core of the issue, but don’t worry; you’ll be able to revive your basil in no time. This article will explore some common causes of brown spots on basil leaves and easy ways to fix them.
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- What Are Brown Spots On Basil Leaves?
- Solutions To Cure Brown Spots On Basil Leaves
What Are Brown Spots On Basil Leaves?
Brown spots on basil leaves can be bacteria leaf spots, pests, downy mildew, or botrytis gray mold. It can also be fusarium wilt, frost damage, cercospora spot. On the other hand, it may also be due to nutritional deficiency, sunburn, or even the lack of sun.
– Bacterial Leaf Spot
When growing basil in your garden, you may find brown spots on your plant’s leaves. The spots usually start light green or yellowish and then turn brown and leaves some spots, these spots may also have a red ring around them, but note that these are through bacteria, that the spots are appearing on the leaves.
What you can do is looking more closely and observe as you would be seeing the spots turning black specks. These specks are the fruiting bodies of the fungus that causes the brown spots, and they are called acervuli. The disease that causes the brown spots is called bacterial leaf spot.
On the other hand, note that many types of bacteria can cause brown spots on basil leaves. The most common one is the Xanthomonas campestris pv. The basilica is a species of bacteria that causes bacterial spot disease on various crops.
Bacterial spot disease is characterized by circular shape and the fading of the color on that shape, in the beginning it would be yellow but surely it will turn brown.
On basil, the spots appear on the lower leaf surface, and chlorotic halos surround the lesions. The spots are minor on the top of the leaf and more significant on the underside. The spots are most prevalent on leaves under water stress and are caused by bacteria that travel on splashing water.
Any plant that is grown outdoors is susceptible to a variety of pests, these can be anything from caterpillars to even unwanted weeds that would grow. No matter what plant you have, pests will want to eat it.
Always check for thrips, spider mites, and aphids when growing basil. These pests can wreak havoc on plant growth and produce black or dark stains on the leaves, which are simply indicators of the insects’ feces.
Aphids are the most common garden pest and are tiny sucking insects that produce a sweet substance called honeydew. Aphids are tiny soft-bodied insects that drain sap and nutrients from the leaves and stems of your plants.
They can be a problem on basil brown plants because they can transmit disease to your plants, and as a gardener, you need to take steps to prevent this from happening.
These pests would surely include some damage symptoms such as a sticky black material on the foliage, curled and spotted leaves, and stunted growth, in addition, you would see the plant stressed through the brown circles on top of the green and aromatic leaves.
– Downy Mildew
Basil is also commonly affected by downy mildew, a fungal disease. It is caused by the fungus Peronospora Bellaria, which is spread by wind-blown rain, by splashing water, or by infected plant material.
On the other hand, some infected garden tools can also spread them, because basil is a very mildew-resistant plant. The disease is likely to attack basil plants that are already stressed, such as those in poor soil or too much water or too little water.
Downy Mildew can be a significant problem for basil growers in the subtropics and tropics, but it is rare in temperate regions, though it may be a problem in greenhouses.
A fungal infection causes basil downy mildew. It begins as little gray spots on the underside of leaves and gradually spreads to cover more significant sections of the bottom leaf surface. The fungus may seem elevated from the leaf surface.
– Botrytis Gray Mold
Botrytis gray mold is a prevalent disease that would impact a wide variety of herbaceous and woody ornamentals, including most vegetable species. The fungus botrytis cinerea causes botrytis blight, and although it can be found worldwide and infect almost any plant, it is more common in warm and humid climates.
However, they won’t kill the plant, as the mold can spread and turn the leaves brown. This one is distinguished by dense fuzzy gray-to-brown fungal growth on basil leaves and stems.
It has a fluffier appearance and is more evident than downy mildew, with the darker shades of points. In the end, the diseased leaves will perish and fall off soon, and the plant will die if many lesions take hold of the stem.
Botrytis is a disease of physiologically mature plant parts, and warm, wet conditions favor it. The fungus invades the space between the leaf surface and the epidermis, and in warm, humid conditions, the fungus produces spores that spread to other plants by wind and rain splash. Botrytis is considered the most economically significant fungal disease of potted herbaceous perennials.
– Fusarium Wilt
The brown spots on the leaves are not a disease, but a pest symptom which is through a pest. They are caused by a fungus called the Fusarium oxysporum. This fungus lives in the soil, and when it gets into the plant, it causes the leaves to turn brown and wilt.
These fungi invade the xylem vessels of the basil plant, causing poor growth, wilting, and eventual death of the plant.
The wilt is particularly destructive to basil, because the disease is the key reason why leaves develop some dots of yellow, brown, and black, and then starting at the tip of the older leaves.
The veins of the older leaves usually remain green. If fusarium wilt is left untreated, the entire plant can wilt and die. This pest is not very common, but it can affect any basil.
– Frost Damage
Many gardeners have had problems with brown spots on their basil plants. Frost is among the main reasons behind them. The basil plants can easily be damaged by frost, and the spots result from it, because it is not prone to the extensive cold weather.
It is not a disease, but rather, it is a cold injury due to exposure to freezing temperatures, and the signs that your plant will show means that through this condition, it is highly stressed that it cannot develop, or grow perfectly, due to the lack of chlorophyll function in the leaves. Overall, it is a physiological dysfunction resulting from a rapid temperature change.
These brown spots are characteristic of a sudden loss of cell turgor caused by water freezing within the cells, the chloroplast which is where photosynthesis will take place, but now, it is simply very hard since the plant is under temperature stress.
The frost first damages the leaves, and then the spots appear. The basil plant is easily damaged if it’s not protected from frost.
– Cercospora Spots
Brown spots on basil leaves may even come from another disease that would be affecting the basil plant’s leaves, which is known as the Cercospora, as you look at the leaves closely, you may see the spots beginning to form on the leaves and stems. This is a leaf spot disease caused by the fungus Cercospora.
The spots appear as circular brownish or blackish marks on the leaves surrounded by yellow borders, which is the fading away from the color of the leaves. The spots are curved inwards. The infection impacts the leaves of the basil plant and can also attack the stems, flowers, and seedlings.
The fungus overwinters on infected plant debris around the base of the plant. When new leaves emerge in the spring, the fungus spreads, and spots begin to appear, even through the new blooms, as a result the spots will grow and merge to cover the entire leaf. Then the leaf will fall off, leaving the stems brown and dead.
– Nutriental Deficiency
Basil grows well in well-drained soil rich in nutrients and organic matter, such as compost or decomposed manure. Nutrient deficiency is the most common reason for brown leaf spots on basil. A plant may lack nitrogen due to over-fertilization, too high of a pH, or insufficient organic material in the soil.
The leaves turn brown, and you can see the color on the top side of the leaves. They can also appear on the new basil shoots, but as long as you can water the plant and keep it alive, the shoots will grow, because the plant itself is growing from a stressful environment, which lacks in potassium and magnesium are also common nutrient deficiencies.
They cause chlorotic patches of yellow or brown areas between the veins on the leaves. Older leaves will be impacted first, and the veins will frequently remain green.
Sunburn is the word used to describe the damage caused to plant tissues by excessive exposure to ultraviolet radiation from the sun or sun lamps. Sunburn is usually associated with plants that are exposed to the sun a lot, and the exposure to ultraviolet radiation can be very damaging to plants, hence the spots of brown start to appear slowly on the leaves.
Even though basil enjoys light and heat, it is prone to sunburn. Water resting on the leaves and catching intense light like a magnifying glass is the most prevalent cause of sunburn.
This is another reason it’s critical to water basil from the ground rather than from above. Sunburn can appear as bleached or brown and dead areas on the tops of leaves.
Brown spots on basil leaves are expected when the plant is exposed to too much sunlight. Basil leaves are sensitive to the sun’s ultraviolet rays, which can cause brown spots.
– Lack of Sun
Curled leaves, yellowing and browning, long stems but only a few leaves, and deteriorating plant health indicate that your plant is not receiving enough sun. Having the lacking of light, will lead the leaves to turn brown as they aren’t receiving proper or enough light to be healthy and show their vibrant green colored leaves.
Basil is a tropical plant that thrives in bright sunlight, and it is when the foliage would be at their best, note that it takes between six and eight hours of full or partial sun every day. Sunlight is a vital component of photosynthesis, which allows basil to store energy to create more leaves and expand.
– Lack of Water and Moisture
Brown spots on basil leaves are a common occurrence when growing basil. Brown spots can be caused by insufficient watering of the plant. The basil leaves are going brown because they are not getting enough water to keep them alive.
When basil plants get water, the cell walls of the plant grow, leading to more extensive and stronger leaves. If it’s not getting enough water, the cells begin to shrink, and the plant begins to turn brown. Proper watering habits will help you eliminate brown spots on basil leaves.
Solutions To Cure Brown Spots On Basil Leaves
The Solutions to cure brown spots on basil leaves would be prevent temperature damage and light damage to the plant, provide some shade to it, provide adequate planting space. In addition, avoid over watering, and enhance proper nutrients to the plant.
– Prevent Temperature And Light Damage
Basil leaves can be damaged for various reasons, as some would simply stress the plant through its core through the environmental conditions that might be harm to it, including sunburn, frost damage, or pest infections. To maintain your plant’s health, it is essential to prevent it from common damage.
Water your plants early or late in the evening to avoid the hottest portions of the day and just at soil level to minimize water pooling on the leaves, to avoid this stress. Note that doing so will also aid in the prevention of bacterial and fungal illnesses.
Basil is a subtropical plant that is quite susceptible to low temperatures. Unfortunately, if your entire plant has been damaged by frost, it cannot be saved. It’s preferable to uproot the entire plant to avoid attracting pests and illness as it decomposes. However, if only a portion of it was impacted, it may be fine.
On the other hand, you might also remove all damaged leaves and stems, and protect the surviving plant from cold temperatures by covering it when frost is forecast, and this will help the new blooms to come out in a healthy environment.
– Provide Some Shade
In order to avoid the plant from being damaged all over, or to spread the sun damage, you can cover the plant and provide proper shading to the leaves.
Covering the plant with a protective cloth prevents these brown spots from further browning. The cloth should be removed during the day, so the plant can quickly get the sunlight it needs, but not very directly and not in a harsh manner.
The brown spots can also be removed by using a sharp knife. Note that here, you must gently scrape off the brown spots. If the entire leaf is brown, the leaf should be discarded.
– Provide Adequate Planting Space
The spacing of plants is an essential consideration in planning a vegetable garden. If plants are too close to each other, they will compete with one another for sunlight, water, and nutrients, and one will always get the share of the other, which will leave the plant will lack of water, or the lack of sunlight because the other is growing in complete shade.
If they are spaced too far apart, there is a greater chance that weeds will appear, and your plants may be more susceptible to pests and disease.
Proper spacing not only helps to optimize growth and development, but also helps save water and time. Use proper spacing, often four to eight inches apart or broader if in a humid location.
Note that you should be keeping your basil plants somewhere between 13 and 15 inches away from each other, so that they would grow on their own pace, and none will be lacking any nutrients that are needed in order to grow.
When they grow properly, in their adequate space, the plants will not be stressed, and this is will be seen through their growth rate and the green color of their leaves, which wouldn’t show any spots on top of it.
– Avoid Overwatering
Excessive wetness in the soil produces root rot, resulting in the basil plant’s black stems and leaves because the roots cannot absorb nutrients. What you must do is to place the plant in a location that gets lots of sunshine to retain humidity—only water when the topsoil seems dry. Ensure that the pot has drainage holes at the bottom as well.
Brown spots on basil leaves are a widespread problem with basil that can develop if you overwater the plants. A fungus causes brown spots on basil leaves. Since this fungus is an opportunistic pathogen, it will develop on stressed plants. It is also a parasite meaning it kills off the host plant.
As a result, this fungus can quickly kill your basil plants if they are overwatered. It is essential to water your basil plants only when they are dry.
– Enhance the Required Nutrients
Your basil leaves can be deficient in nutrients like nitrogen, potassium, or magnesium, and this will be seen through the foliage, as they would start slowly losing their green color.
Treatments for potassium deficiencies generally consist of a fertilizer application. Check the NPK ratio, which is the nitrogen to phosphorus to potassium, on the label and choose something with lots of potassium but not too much nitrogen.
Another nutrient lacking is magnesium, which can be corrected by watering with a quarter of a teaspoon or Epsom salt per gallon of water.
If your plant is developing its growth in a pot, you may then add a two to three inch layer of some mulch around the root zone because this will help it to retain moisture and prevent the soil from drying out.
If you suspect a magnesium deficit, water your plant with an Epsom salt solution known as magnesium sulfate. Epsom’s salts are an excellent nutrient source for your plant.
– Is It Dangerous To Eat Brown Basil With Bacterial Leaf Spots?
If the leaves on your basil plant have black spots, they are still edible as long as they are not sick or treated with chemicals. However, the flavor of the leaf may change slightly. So, you can eat basil. Damaged basil leaves can taste unpleasant and be sticky if severely spotted or damaged.
If you want to grow your own basil plant, you will want to know more about it. One of the things that you might notice is that your basil plant has brown spots on the leaves that it is growing. The universal solution to preventing basil plant damage is to maintain them healthy in the first place!
Here’s a summary of what you just read:
- Grow your basil leaves on well-drained soil. Use appropriate placement between four and eight inches, apart, or wider if in a humid location.
- Brown spots on basil leaves are a common symptom of overwatering, and they can be avoided if you maintain proper watering schedule.
- Brown spots on basil leaves can also be a fungus symptom, which can be treated using plant disease-resistant cultivars.
- You can always keep it safety away from the frost by protecting it.
- You can improve the plant’s growing conditions by providing it with adequate humidity or shade.
We hope you now have a complete knowledge of the problems of basil plant and its solutions. Go on planting and healing your plant.
- Basil. PlantVillage.
Retrieved from https://plantvillage.psu.edu/topics/basil/infos
- Zayda Piedad Morales Moreira, Patricia Oliveira dos Santos, Thiago Alves Santos de Oliveira, Jorge Teodoro de Souza. (2015). Occurrence of basil leaf spot caused by Pseudomonas cichorii in Bahia State, Brazil. SciELO.
Retrieved from https://www.scielo.br/j/sp/a/9BmnwCQtFdPyWRjk9jd9WBD/?lang=en