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Speckled basil leaves: possible causes and remedies. Diseases of basil, what to do if basil has yellow leaves or leaves with dark spots. Basil with black leaves.
Basil is undoubtedly the most cultivated plant of the summer: it requires little space, looks good on the windowsill and gives off a pleasant scent! It is true that basil is easy to grow but it is also true that this plant is not immune to diseases.
Basil plant with yellow leaves
If the basil is potted, you have most likely noticed the appearance of yellow leaves or leaves that first have white spots and then turn pale. This disease is linked to soil imbalances: you are most likely irrigating the plant with excessively calcareous tap water. Limestone raises the pH of the soil and the plant is no longer able to absorb certain nutrients. Thus, the basil leaves begin to turn yellow.
If the basil leaves turn yellow, show white spots and then turn pale, start irrigating the plant with rainwater or, if it's a drought period, use distilled water. You can buy distilled water at the grocery store or get it from your air conditioner. Distilled water is free of limescale and will allow the plant to absorb the necessary nutrients by modifying the pH reaction of the soil (lowering the pH). If you want to speed up the greening of basil leaves, administer an iron-enriched fertilizer such as the "Cifo green fertilizer". The fertilizer in question costs € 9.90 and has an excellent yield.
There are many iron-based fertilizers on the market, make sure you buy one based on "chelated iron" and above all do not overdo the doses. A single fertilization is enough if you correct the irrigation. The ideal would be to irrigate the basil with rainwater.
For further targeted information, I suggest you read the article: Basil with yellow leaves.
Speckled Basil Leaves: Basil with black leaves
If the basil has leaves with white spots, it may be an alteration in the pH of the soil as described above. If the basil has leaves with dark or black spots ... depending on the type of spot, it can be:
- burnt leaves, if you have wet the leaves and the plant is in full sun. The heat may have burned the leaves near the water droplets. The spots appear dried out.
- Leaves with rot, the plant is in a very humid environment and you are overdoing it with watering.
- Downy mildew, this infection is manifested by spotted leavesand covered with amoldbrown in color.
Downy mildew is a very common fungal disease in the vegetable garden: the leaves of basil appear covered with brownish spots. Initially, the disease appears with a yellowing of portions of the leaf limb and, after a few days, follows the development of a brown mold which gradually covers the leaves until theyblackencompletely and dry out. The black basil leavesonce dried, they remain attached to the plant.
Thebasil plantsmost affected by this disease are those placed in poorly ventilated, very humid environments where the vegetation is such as to allow the development of mold and fungal diseases.
To prevent this disease from appearing, remember to ventilate the plants well, thinning the basil as the leaves mature and are ready for cooking.
Another good idea is to irrigate the basil plants early in the morning: avoid watering the basil in the evening and avoid wetting the leaves but only wet the soil. The high humidity level supports the development of downy mildew.
If yours basil plant presents spotted leaves, leaves black and with dark spots, thin the plant and carry out targeted treatments.
Remember, however, that after the treatment you will have to wait for the safety time to be able to collect the leaves and use them in the kitchen.
What product to use to treat a sick basil plant?
If the basil plant is attacked by late blight or other fungal diseases, you can use Bordeaux mixture.
Bordeaux mixture is a product based on copper sulphate and slaked lime. It is a plant protection product allowed in organic farming. You can easily find it at agricultural consortia, resellers of phytosanitary products, garden centers and nurseries, or you can buy it using the online purchase: on Amazon, for example, a bag of Bordeaux mixture can be bought at the price of 11.30 euros with shipping costs free. For all information on the product mentioned, I refer you to the Amazon page: Bordeaux mixture.
How to use it? Weigh 100 grams of powder and add it to 10 liters of water, mix and sprinkle the plant. If there is only one plant to be treated, 25 grams in 2.5 liters of water will suffice. Keep in mind that, for the product I have reported to you, the safety time (therefore the time interval that will have to pass between treatment and harvest) is only 7 days. On the label it says that 3 days are enough, this is true but for vegetable crops (tomato, eggplant, potato ...) when it comes to herbaceous plants (therefore from leaves, such as sage, basil and other aromatic) the time security doubles.