It's just spittlebug nymph's froth. Fairly common this time of year. Use the hose to wash it away easily. No need to blast them with water, a medium spray will dislodge them. The consistency of the foam is like spit - hence the name - or soapsuds.

Here is a link that might be useful: Spittlebugs

This post was edited by vasue on Sat, May 24, 14 at 10:16