Question
I have a large White Pine in my yard in northern IL.  There are little globs of foam on branches.  What is this?

Answer
This is an insect called a spittle bug.  The pine spittlebug, Aphrophora parallela (Say), is "often abundant on white, jack pines as well as other conifers". Other conifers being balsam fir, tamarack and spruce. And in fact, several Christmas tree growers in the north central counties reported the occurrence of this insect in their balsam fir fields this summer.
Spittlebug eggs overwinter on the tips of twigs. On hatching in the spring, the young pierce the bark to feed on the sap and soon cover themselves with a frothy mass of spittle made up of tiny air bubbles coated with the partially digested sap . The bubbles protect the insect and are formed by a series of movements of the abdomen while the young spittlebug is feeding. From May to July, the young move periodically inward on the branch and when full grown, in July, they have usually reached the main stem where many bugs often feed together under large masses of spittle. When the young change to adults in July, the spittle masses soon dry up and a black sooty mold often develops at feeding sites. The adults, which are from to ?inch long, also feed on the tree's sap throughout July and August but do not form spittle. They do, however, eject undigested sap in the form of a fine mist that drops from heavily infested trees like very light rain. Then sooty molds can infest the honeydew.

Heavy infestations of spittlebugs may cause twig, branch and tree mortality the following year. In natural stands, spittlebug population build-up is often prevented by a fungal disease caused by Entomophthora aphrophora. In plantations, control may be required and since the spittle masses give protection to the young, contact insecticide sprays must be applied with force before mid-July.  An insecticide called Orthene will work well. Check with your local nursery for this product.