How can decay in a tree be identified?

Identifying decay in a tree is most effectively accomplished through a combination of visual inspection, probing, and sound testing for hollow spaces. This approach allows for direct assessment of the tree's condition. Visual inspection involves looking for signs such as discolored or missing bark, fungal fruiting bodies, or changes in leaf color and overall vigor. Probing with tools can help detect softer or compromised wood within the tree, indicating potential decay. Additionally, sound testing can reveal hollow areas within the trunk or branches, which are often indicative of advanced decay.

While other choices may provide some information about a tree's health, they do not offer as direct an assessment as the methods outlined in the correct answer. Analyzing the soil can give insights into root conditions but doesn't directly measure decay in the wood. The presence of insects can signal deterioration but is often a secondary indicator and does not confirm the extent or presence of decay. Laboratory analysis, while precise and useful for specific cases, is typically not necessary for initial identification and may not provide immediate insights into the structural integrity of the tree. Thus, the combination of visual inspection, probing, and sound testing remains the most effective method for identifying decay.