I like to grow basil as part of my fragrant and flavorful herb garden. But I found some white spots on the basil leaves and wanted to know what it is. This post contains my research on this problem and how you can solve it.
There are white spots on your basil leaves because they have been attacked by pests like aphids, thrips, or whiteflies. They could also be due to a fungal disease like powdery mildew. Some other causes of such white spots could be a lack of nutrients or salt deposits on the basil leaves.
I’ve written a lot more details about each of these issues that can cause white spots on the leaves. You’ll also find some preventive measures and solutions that will help you get your basil plant and leaves healthy again.
Attack by pests
There may be white spots on your basil leaves because of pests like aphids, thrips, whiteflies, leafhoppers, and mealybugs.
Some of these insects like aphids and thrips will suck the sap out of the leaves and cause white marks on them. You may see the tiny white aphids on the leaves and think they are white spots on them. Pests like mites will leave white webbing on your leaves.
It’s easy to get rid of pests like aphids and thrips using a spray of water on the leaves where they are nesting. Make sure to check the underside of the leaves as well.
The spray of water will dislodge these pests and drop them into the soil. And they will be unable to get back on the plant from there.
Another option to get rid of pests on your basil leaves is to use a spray containing neem oil. You can mix 2-3 tablespoons of neem oil in a gallon of water. Then spray this on your basil leaves to eliminate the pests.
Insecticidal soap is another option that is beneficial to get rid of pests. You can make some of your own by mixing a cup of vegetable oil with a tablespoon of dishwashing soap.
You can mix two teaspoons of this insecticidal soap with 2 cups of water and spray the mixture on the basil leaves to get rid of the pests.
Infection of fungal disease
Your basil plant can get infected by a fungal disease like powdery mildew. The characteristic of this disease is that it leaves a powder-like material on the leaves.
The most common reason for fungal disease on the basil plant is if you’re splashing water on the leaves. This causes a moist environment to develop on the plant that attracts fungal diseases.
Another reason why the basil leaves could get a fungal infection is if you’re splashing soil on the leaves when watering. The fungal diseases present in the soil will attack the leaves.
In small amounts, the powdery mildew is not harmful to the basil leaves. However, it will keep spreading and cover the entire leaf. This will impair the photosynthesis and the plant won’t be able to produce enough food.
This will cause stress to the basil plant that will attract more pests and diseases and even end up killing the plant due to lack of nutrients.
The best solution to protect your basil leaves from fungal diseases is to avoid splashing water on the leaves when watering the plant. You can use a watering can, soaker hose, or drip-irrigation to water the plant. Avoid using a garden hose or a sprinkler system that sprays water all over the plant.
You can consider growing varieties of basil that are resistant to some of the fungal, bacterial, and viral diseases. If you find some of the basil leaves are infected, the best solution is to cut these leaves from the plant and dispose of them.
You can use a mixture of 1 tablespoon baking soda, 1/2 teaspoon dishwashing soap, and a gallon of water to create a preventive mixture. Spray this on your basil leaves every few days to prevent fungal diseases from attacking them.
Another option is to mix 2-3 tablespoons of apple cider vinegar with a gallon of water and spray this on the basil leaves every few days.
Salt deposits on the leaves
If you live in an area that gets hard water, it will contain a lot of minerals and salts. You may use such tap water on your basil plants and when it evaporates, the white salt can get deposited on the leaves.
I would suggest not to use such hard water on your plants because the residue will collect in the soil and eventually harm the roots of the plant. It’s better to use rainwater that you collect or distilled water. It may be expensive to buy distilled water so it’s better to get a distiller or make one yourself.
The rainwater is the best water you can use as it’s pure but contains the minerals and nutrients that are beneficial for the plants. If you use distilled water you need to make sure to use a good fertilizer that will provide some nutrients to the basil plant.
Lack of nutrients
If your basil plant is not getting the required macro and micro-nutrients from the soil, there is a possibility that the leaves may have a lack of chlorophyll. This may appear as white spots on the basil leaves.
I would recommend using either a slow-release fertilizer or a liquid fertilizer for the basil plant. You can use a balanced fertilizer when starting to grow the plant. But once it’s grown, you can use a nitrogen-rich fertilizer that will encourage the growth of the basil leaves.
You can mix the slow-release fertilizer along with the potting mix when preparing the soil. This fertilizer will release in the soil as you’re watering the basil plant. If you can get some organic compost, that’s even better to add to the soil. You can add such slow-release fertilizer once every month when the basil plant is growing.
The other option is to use a liquid fertilizer that you spray on the soil and the leaves. This is a fast-acting fertilizer that is quickly absorbed into the plant. I would suggest spraying the liquid fertilizer once every couple of weeks.
You can spray the liquid fertilizer every day if you dilute it a lot with water. This would be like diluting 1 tablespoon in a gallon of water. Then you can add it to the watering can when watering the basil plant.
Some other options you can use include compost tea that is a very diluted version of compost that you can spray regularly on your basil leaves to provide them with nutrients.
Make sure to spray the liquid fertilizer in the morning. If you use after the sun comes out, the liquid can heat up and burn the basil leaves.
I would recommend following the instructions provided by the fertilizer manufacturer to figure out how much fertilizer you need to use and how often you need to use it.
The leaves of your basil plant can suffer environmental stress from wind, heat, and cold. The basil leaves may even curl as they try to protect themselves from the harsh sunlight or wind. This can cause the leaves to receive limited sunlight and develop white spots.
This is nothing to be concerned about because once these environmental issues get resolved, the leaves will go back to being normal. You can help the leaves by placing a windbreaker or a row cover that protects them from the intense heat or strong winds.
If you’re growing the basil plant in a container, you can move the container to a location that is protected from these environmental conditions. You can even move them indoors for a short period of time.
Basil variety with white leaves
Some varieties of basil like Pesto Perpetuo can have white marks on the leaves which is completely natural. So when growing basil make sure you know what variety it is.
And if it’s the variety that has white areas on the leaves, there’s nothing you need to worry about.