Is your tree on death's door? Here's how to tell

Worried about a sad-looking tree in your yard?

Climate change, invasive species and even international trade are taking a serious toll on California trees. An estimated 150 million trees died during the drought that started in December 2011, according to Smithsonian Magazine, and the stressed trees that survived became more vulnerable to attack by a host of newcomer pests, said Philippe Rolshausen, subtropical tree specialist for the Cooperative Extension office at UC Riverside.

"There are lots of invasive pests everywhere because of global warming and the movement of plant materials in general," he said.

Identifying specific tree diseases or pests usually requires an expert, but Rolshausen said three indicators suggest your