Rosemary is a very aromatic and he althy herb - not only we humans appreciate it, but also a whole range of pests. White dots or spots on the rosemary leaves can have very different causes.
What causes white spots on rosemary leaves?
White spots on rosemary leaves can be caused by leafhoppers, spider mites or powdery mildew. Repotting the plant can help against leafhoppers, rinsing it in the shower against spider mites and removing infected parts of the plant and spraying it with a milk-water mixture or garlic decoction can help against mildew.
Leafhoppers
Bright spots on the top of the leaves, usually yellowish-white to yellow, usually come from leafhoppers, which are usually no larger than a maximum of two millimeters and have wings. The animals are very agile and not only hop around on the plant, but pretty much everywhere. Leafhoppers suck out the cell sap of the infected plants, which also creates the bright spots - these are simply the puncture sites. Infected plants should be repotted as quickly as possible.
Spider mites
Spider mites, on the other hand, appear mainly towards the end of winter. They love dry and warm air and prefer to colonize plants that are already weakened. A spider mite infestation can initially be recognized by small, yellowish-white spots. However, the leaves later turn gray, then brown and finally fall off. In addition, the spider mite - hence its name - forms fine white webs primarily in the leaf axils. This is her preferred place of residence and this is also where she lays her eggs. The spider mite also likes to feast on plant sap. Plants infected with spider mites should be rinsed vigorously in the shower and also washed with a soft soap solution.
Mildew
Mildew is not a pest, but is caused by a fungus. Rosemary is primarily affected by powdery mildew, which occurs primarily on warm and dry days. You can recognize a powdery mildew infestation by the white, powdery coating, primarily on the upper sides of the leaves - the plant literally looks like it is dusted with flour. The first step in combating the disease is always to remove the affected parts of the plant as the fungus spreads very quickly. You should also spray the plant with a milk-water mixture or with garlic decoction and repeat the treatment on several days in a row.
Tips & Tricks
Many pests love dry air, which is why you can often prevent an infestation by increasing the humidity. To do this, spray your rosemary all over regularly in summer or shower the plant.