Herbs are usually trouble-free plants, but there are a few pests and diseases that may cause problems;
Damping off can occur in growing environments that are badly ventilated or humid. Mint rust can affect marjoram and savory as well as mint species.
Rosemary beetle can be a problem on lavender, sage and thyme as well as rosemary. Sage leafhopper is also responsible for causing fine, yellow flecking on the foliage of many aromatic plants including sage, mints, lavender, bergamot, marjoram, oregano, rosemary, basil, thyme and lemon balm. Only treatments suitable for edible plants (as described on the label) should be used.