As a horticulturist, I am often faced with questions for people about some strange things that they observe on their plants.
One of the most interesting symptoms are what look like ‘gobs of spit’ on their plants. Now, it isn’t caused by someone actually ‘spitting’ on their plants. Rather the culprit is a bug, commonly referred to as a spittle bug.
Spittle bugs are sucking insects that appear in spring, usually in humid climates (although I have seen my share in the desert, where I live). In their immature stage, spittle bugs attach themselves to a plant and secrete a frothy liquid to help protect themselves from the sun and other predators (such as birds) while feeding. I often find them feeding on rosemary and occasionally on salvia, but they like all types of plants including wildflowers and grass.
The good news is that if you are going to have an insect problem – spittle bugs aren’t all that bad. First of all, they don’t do much damage to the plant. So in most cases, if you do nothing – your plant will probably be just fine.
But, if you really don’t like seeing small gobs of ‘spit’ on your plant, all you need is to spray the spit and bugs off with a strong jet of water from your hose. This separates them from your plant and ‘washes’ off their frothy covering, which is bad news for them because they are now visible to birds who find them delicious 
