The substance you see on the grass I believe is actually the foam produced by the spittlebug a member of the cercopoidea insect family.  They most resemble leafhoppers because they can jump long distances.

As nymphs of immature bugs, they feed on the blades of grass, The sap that they excrete mixes with air to make the foam white substance that will eventually encase them. The foam helps the nymph cling to the grass and gives a protective coating. Once they reach a mature stage they stop feeding and producing foam as they emerge fully as a  developed spittlebug. 

They typically feed on legumes  and grasses, but you can find them on other plants.  They can cause serious damage to corn, sugarcane and pasture grasses. Most of my research says they are not a real threat unless you feel the infestation is severe and you see your grass dying as a result of them feeding. 

As far as how to eradicate,  you can pull off the foam casings from the grass, squeeze the lymph from it and drown them in soapy water.  a pesticide listing spittlebugs can also be applied to your lawn to control the infestation.

Here are a few articles about them. 

https://bugs.uconn.edu/2017/07/24/spittlebug-a-unique-little-insect/
https://extension.umn.edu/yard-and-garden-insects/spittlebugs