If white spots appear on a lemon balm, quick help is usually required. Read about the possible causes and ways to combat them here.
Table of Contents
Lime stains
If white spots form on the leaves of lemon balm (Melissa officinalis), this does not necessarily have to be due to diseases or pest infestation. It can also be due to watering with hard water. Especially if the leaves get wet. In this case, a white layer of lime deposits, which can have a wide variety of shapes and sizes. These should be wiped off with a damp cloth so that the leaves can “breathe” unhindered. In the future, the lemon balm should only be watered in the soil area.
nutrient deficiency
If there is a lack of nutrients in the soil, the lemon balm usually shows this with the formation of white spots. Heavy-duty herb and vegetable beds in particular therefore need regular fertilizer to prevent this deficiency. A rapid “re-fertilization” stops the damage process.
sunburn
If the sun shines too strongly and hot on a lemon balm, white spots are often a reaction to sunburn. If the leaves get wet while the sun is shining, this favors a sunburn immensely.
The correct help looks like this:
- remove affected leaves
- Give the plant shade for a short time
- preventive: only water the soil in the morning and/or evening, without wetting the leaves; Keep planting distance to plant neighbors so that summer rain dries off faster
leaf spot disease
Leaf spot disease is caused by a fungal infection of sac fungi from the Septoria melissae genus. Immediate action is required here to prevent the lemon balm from spreading and dying off. The main causes of infestation include a lack of light, nutrients and aeration, as well as sunburn and incorrect fertilization.
damage picture
- whitish, white-greyish point-like spots in the early stages
- later light yellow marginal zones
- brown discolouration around white patches as the course progresses; lead to leaf desiccation
- often also reddish spots in the middle of the leaf
- growth disorders
Fight
- Isolate affected plant immediately to prevent spread
- Cut back infested plant parts (are burned or disposed of with organic waste – not in the compost!)
- If the infestation is very severe, discard the whole plant
- Prevention: Ensure good ventilation between plant neighbors so that good drying works
mildew
Powdery mildew is one of the fungal diseases that often occurs in herbs and especially in Melissa officinalis. A distinction is made between powdery mildew and downy mildew, with the former occurring more frequently in lemon balm. If no countermeasures are taken, the plant will die.
damage picture
- Powdery mildew : large, wipeable white deposits on the upper side of the leaves; initially punctiform staining
- Downy mildew : whitish-grey deposits on undersides of leaves; usually in combination with light leaf spots on the upper side of the leaf
- sticky plaque
- At a later stage, the leaves dry up and the plant dies
combat
No matter what type of mildew it is, using baking soda is very reliable. It creates an alkaline reaction which has a killing effect on the fungus. The home remedy is easy to prepare yourself for the fight. That is how it goes:
- Pour two liters of water into a bowl
- stir in a pack of baking soda (sodium bicarbonate).
- Add 20 milliliters of cooking oil
- Pour the mixture into a spray container
- Spray lemon balm until dripping wet; Don’t forget the underside of the leaves!
- Frequency: every three days
- Duration of use: two weeks
- can also be used preventively every two weeks
- Alternative: Mix fresh milk with water in a ratio of 1:8 and spray
spider mites
If the weather is dry and warm, the risk of spider mite infestation is high. They suck the sap from the leaves of lemon balm, causing white spots.
Detect spider mite infestation
- small, white dots on leaf surfaces
- white webs initially mostly between stems
- in the advanced stage, webs take up the entire plant
- progressive drying out of the foliage
Fight
- Cut 20 grams of soap per liter into small pieces
- Add soap bars to hot water and stir vigorously to dissolve
- Let the mixture cool down
- Fill the spray container with the lye and spray the infested plants until dripping wet
Zikaden
Cicadas are pests, of which the leaf cicadas in particular have a special fondness for herbs. They suck the sap from the leaves with their suckers. They are particularly active on warm sunny days. A small infestation does not require control. However, when more and more animals show up, help is needed.
Recognize
- Size of the pests: between two and 3.5 millimeters
- Body color: green with black dots in the head area
- chirping noises
- fly, jump and run
- irregular white, white-silver leaf mottle
- increasing brown leaf colour
- also affect flowers
- increased susceptibility to fungal infections
- without early countermeasures, the plant dies
Fight
Cicadas can be stubborn creatures that are difficult to control. The following measures are among the most effective and are best carried out early in the morning when hunger brings the pests onto the plant:
- Dilute vinegar essence in a ratio of 1:2 with water and spray lemon balm, especially on the underside of the leaves (to expel)
- Use of natural predators such as predatory mites, ground beetles, numerous species of spiders, ants, birds and parasitic wasps
- Sprinkled with sugar water around the plant attracts ants
- Set up yellow boards and/or stickers near the plants
- Preventively pollinate the plant with rock dust in spring and autumn
frequently asked Questions
That depends on the causes. In the case of an existing fungal infestation, consumption is not recommended because it can cause allergic reactions in sensitive people. These include, for example, abdominal pain and skin irritation. Pest infestation by said species will maximally affect the herb in the early stages with a drier aroma. Make sure you wash the lemon balm thoroughly after harvesting and before processing to remove any pests that may be present.
The white spots not directly, but the diseases and pests that cause them can spread to neighboring plants and cause white spots there as well. Most often this happens between different herb species and/or too close a planting distance.
