Rosemary is a very aromatic and healthy herb - not only we humans appreciate that, but also a whole range of pests. White dots or spots on the rosemary leaves can have very different causes.
leafhoppers
Bright spots on the upper side of the leaves, usually yellowish-white to yellow, usually come from leafhoppers, which are usually no larger than a maximum of two millimeters and are winged. The little animals are very agile and don't just hop on the plant, but pretty much everywhere. Leafhoppers suck out the cell sap of the affected plants, which also causes the light spots to appear - these are simply the puncture sites. Affected plants should be repotted as soon 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 already weakened plants. A spider mite infestation can initially be recognized by small, also yellowish-white spots. Later, however, the leaves first turn grey, then brown and finally fall off. In addition, the spider mite - hence its name - forms fine white webs, mainly in the leaf axils. This is where she prefers to stay and where she lays her eggs. The spider mite also likes to feast on the plant sap. Plants infested with spider mites should be rinsed off vigorously in the shower and also washed off with a soft soap solution.
mildew
Powdery mildew is not a pest but is caused by a fungus. Rosemary is primarily attacked 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 side of the leaves - the plant literally looks like it has been dusted with flour. The first step in combating this is always the generous removal of 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 broth and repeat the treatment for several days in a row.
tips and 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 regularly all over in summer or shower the plant.
IJA