There are small, white objects resembling kernels of popcorn on the branches of my silver maple tree. What are they?

FAQ
Question: 

There are small, white objects resembling kernels of popcorn on the branches of my silver maple tree. What are they?

Answer: 

The small, white, popcorn-like objects are likely cottony maple scale.  Cottony maple scale is an insect.  It is most commonly found on silver maple trees.  However, it can also be found on other maples, oak, linden, hackberry, honey locust, and other trees.  

In June, female scales begin to produce large, white, cottony egg sacs that may grow to the size of dimes (up to ½ inch in diameter).  Large numbers of egg sacs look like popcorn strung along the branches and twigs.  

The eggs within the expanded egg sacs (up to 1000 per sac) begin to hatch in early July. The new scale nymphs crawl to the undersides of leaves where they feed on sap from the leaf tissue.  The scales grow to adulthood on the leaves and mate in August or September before the females return to twigs to spend the winter.  There is one generation per year.  

Cottony maple scale insects excrete a clear, sticky substance called honeydew.  The honeydew drops onto leaves on the lower portions of infested trees.  It also drops onto plants or other objects (patio furniture, cars, driveways, etc.) beneath trees.   Oftentimes, a sooty mold fungus colonizes the honeydew, resulting in a black sooty appearance on leaves, branches, and other objects.  

Cottony maple scale usually causes little harm to healthy trees.  Natural predators will control the infestation within one or two years.  Treatment of cottony maple scale with insecticides may do  more harm than good as the insecticide will kill their insect predators.