Basil is a culinary herb most commonly used in cuisines worldwide. With bright green short leaves, this plant is a refreshing sight to the eyes and fills the house with a beautiful scent.
However, it is quite common for these plants to develop white spots. Hence, it is crucial to understand the causes of these spots and familiarize ourselves with effective ways of treating them.
What Causes White Spots on Basil?
White spots on basil leaves may form due to a range of reasons. These include fungal infections like downy mildew and white fungus. Other causes include bacterial leaf spot disease and overuse of fertilizers that increase the soil’s salinity leading to water stress. At most times, if the infection has not spread across the whole plant, the white spots can be cured through several organic methods. Preventative measures include appropriate watering routine, drip irrigation method, and maintaining proper plant hygiene.
Causes of White Spots on Basil Leaves
1. Downy Mildew
Caused by Peronospora belbahrii, Basil Downy Mildew is an infection that occurs in wet weather or due to prolonged leaf wetness. It is also prevalent in warm, humid conditions.
The disease is highly contagious and spreads through spores by wind and water.
Initial symptoms are yellowing along the veins on the leaf surface as chlorosis occurs. Over time, white spots develop on the underside of leaves, which gradually turn into black lesions.
If the symptoms are not identified at an early stage and immediate measures taken for treatment, the infection spreads throughout the plant. The leaves droop, slowly turn brown and fall off, and eventually, the plant dies.
2. White Fungus
During the rainy season, your basil plant is highly vulnerable to fungal attack. If the leaves remain consistently moist and the soil soggy, the plant will likely contract a fungal disease.
The white fungus typically grows in damp conditions.
The fungal infection is characterized by fuzzy white outgrowth on the leaves that appears as concentric circles. White mycelium aggregate across the leaf plate and soon hog the plant if left unaddressed.
White fungal infection can kill your plant in no time and is fatal. Therefore, strict preventive measures should be taken to avoid it in the future.
3. Pest Attacks
These pests feed on the cell sap within the leaf, and while doing so, their mouthparts leave behind marks that appear as tiny white dots.
Severe aphid infestation can result in necrotic spots on the leaf plate, necrosis, and stunted growth.
On most occasions, you can recognize that these spots’ causable agents are insects because they live around the plant and can be sighted in the plant’s vicinity.
However, if you are unsure, look for minutiae white spots on the underside of leaves, and you can be almost certain that they are a result of pest attack.
4. Overuse of Fertilizers
Overuse of fertilizers leads to the accumulation of salts in the soil mix. As a result, over time, the soil becomes saline, and its pH is no longer suitable for supporting the roots.
The roots begin to weaken, and the plant’s health takes a toll. Due to the soil’s low osmotic potential, the roots are unable to absorb and transport sufficient water to the leaves.
In reaction to this, white spots begin to appear on the leaves, and the leaves begin to lose color and eventually fall off.
5. Bacterial Leaf Spot
High humidity levels can be disastrous for the growth of your basil plant. It promotes the growth of bacteria called Pseudomonas cichorii that is responsible for leaf spot disease.
Initially, leaves start to pale, and white spots appear across the surface. Soon, the areas darken, and brown edges form around them. You will also observe streaks on the stems.
Over time, tiny black spots form a cluster on the leaves, and if left untreated, they eventually cause plant death.
How to Treat and Prevent White Spots on Basil Plant?
1. Adopt Appropriate Irrigation Methods
Damp conditions trigger infections like downy mildew. Hence, to prevent water from accumulating in the soil, it is crucial to adopt better irrigation methods.
You can try using a drip or furrow irrigation system as it ensures the soil remains moderately moist. However, if you only have a small houseplant of basil, you can also use a hand sprinkler.
2. Use Effective Organic Methods
Plant specialists usually recommend using organic methods to treat pathogenic infections over synthetic chemicals. In the case of edible plants like basil, the use of chemicals may declare them unsafe for consumption.
For instance, in case of downy mildew and pest attacks, you can treat your basil plant with insecticidal soap rich in potassium-based fatty acids.
Applying the mixture of soap and water on the infected leaves for a short period is highly effective and helps cure it. Of course, the sooner you tend to the infection, the higher chances you have of saving your plant.
Furthermore, potassium bicarbonate and copper solution can be used to kill off any fungi. If you spot white fungal outgrowths on the basil leaves, you can try washing them with an alkaline solution like potassium bicarbonate, as it inhibits the growth of fungi.
3. Use a Well-Drained Soil Mix
To ensure the healthy growth of plants and bar entry of any pathogens, it is essential to use a well-drained soil mix. It has pores that allow the circulation of air, which helps fulfill the roots’ oxygen needs.
Lack of aeration leads to nutritional deficiencies and hampers the normal functioning of plant cells. To remedy this, make sure that your soil mix contains organic fertilizers.
4. Maintain Plant Hygiene
Lastly, maintaining proper plant hygiene is imperative as it wards off pest attacks. Insects like red spider mites are attracted towards plants having dusty leaves and poor hygiene.
Take appropriate care of your plant, wipe off grime on leaf plates, and look out for any insects residing in the soil. Give the plant proper attention, and you are assured not to worry about any white spots in the future.
Frequently Asked Questions About White Spots on Basil
Can you eat basil with white spots?
The most common causes of white spots on basil leaves are fungal infections, like downy mildew. Though basil leaves infected with downy mildew are not toxic, the fungal growth can be detrimental to your health.
Therefore, it is strictly advised to throw away plants infected with fungal infection and not consume them.
Will the white spots go away on their own?
It is improbable that once the plant has developed white spots, it will go away on its own. They usually appear as a result of infections and without the intervention of synthetic or organic fungicides, the disease will only spread. If the infection is left unaddressed, it will soon overcome the whole plant, causing it to die.
Marcel runs the place around here. He has a deep passion for houseplants & gardening and is constantly on the lookout for yet another special plant to add to his arsenal of houseplants, succulents & cacti.
Marcel is also the founder of Iseli International Commerce, a sole proprietorship company that publishes a variety of websites and online magazines.