Spittle bugs are insect pests that infest rosemary plants and may cause significant damage but generally do not kill the plant. To prevent this infestation, always keep your rosemary plants vigorous through proper maintenance. Identify characteristics and symptoms of the presence of spittle bugs and apply proper control methods for healthy plant growth.
Spittle bugs are inconspicuous but resemble leafhoppers in their adult form. They are narrow and green to brown in color, measuring approximately 1/4 inch in length. Young spittle bugs make their presence easily detectable on plant surfaces by covering themselves in a white mass that looks like froth, referred to as spittle.
Adult female spittle bugs lay eggs in enclosed, protected areas of the plant unnoticeable to the human eye. They lay eggs in rows, and hatched nymphs molt up to five times, revealing different colors like yellow, orange or green. When you remove spittle from plant surfaces, nymph or adult bugs are made visible. Adult spittle bugs generally have one to two generations annually.
Spittle bugs are parasitic infestations that feed on plant tissue by sucking fluids. They generally feed within the spittle masses. Though infestations are not usually severe, in extreme cases the rosemary plant may suffer from yellowing or stunted growth. Most often, however, damage is cosmetic or unnoticeable.
Healthy plants are more capable of bouncing back from or avoiding pest infestation, so keep your rosemary plant vigorous. Rosemary thrives in full sun and prefers well-drained soil. Keep the soil pH at a range of 6.0 to 7.5. Climatically, rosemary must be kept above 27 degrees F. The 'Alba' variety must remain above 10 degrees to avoid injury.
To control spittle bug infestations of rosemary plants, consider the level of infestation. For a mild infestation, it is okay to ignore them, as they will not cause any substantial harm to your plants. If they bother you, wash them off with a powerful water source. If you notice spittle bugs on neighboring plants, wash the bugs from these plants before they spread to your rosemary. Keep weeds out of the garden area, as they often act as hosts to spittle bugs. To rid an infested area of the problem, you may prune or remove the entire plant. No chemical control is recommended for spittle bug management on rosemary.