Is this a benign spider web?
The white spots are out of focus and we cannot identify them. It is possible they may be spider eggs. In general, spiders are beneficial and keep insect pests in check. They are not a reason for the decline of the tree.
The tree is dead and you will have to remove it. We do not know how old the tree is and how you cared for it. There may be several reasons for dieback including too much moisture, not enough moisture, planting too deeply; poor drainage; if a container plant, were the roots teased apart so they could grow into the native soil; if you added a lot of organic matter into the planting hole you may have created a bathtub effect as water sits in the planting hole and drowns the tree. Take a look at our website for the planting process, video (explains the process), and aftercare. http://extension.umd.edu/hgic/plants/planting-process
Too much mulch around the trees and/or planting too deeply can result in decline over time. You should be able to see the flare of the trunk where it joins the root system. We do not see this. Make sure mulch is no thicker than several inches and away from the base of the trunk.
Do not overwater. Plants less than two years old should be watered deeply once or twice per week up until the ground freezes. This encourages roots to grow deeper. More frequent, light watering only wets the surface promoting a shallow root system. Soil should be damp like a wrung out sponge. After watering, probe with a screwdriver to make certain the soil is moist down six inches or more.
Weather conditions over the last two years or so have been tough on a number of plants. We had an excessive amount of rainfall in 2018 and into the spring of 2019. Plants in saturated soil can experience root decline due to lack of oxygen and/or root pathogens. Then in late summer 2019, there was a drought. So, trees with impaired root systems would have a tougher time to take up water during dry conditions. This leads to poor overall growth and decline symptoms.
Here is more information on when to remove a tree https://extension.umd.edu/hgic/topics/how-do-you-decide-when-remove-tree