Which of the following is NOT a sign of decay in trees?

Healthy bark is indicative of a tree that is generally in good condition and free from decay. The presence of healthy bark suggests that the tree's protective layer is intact, allowing it to effectively defend against pathogens and environmental stressors. In contrast, the other choices are associated with decay or damage in trees.

An open wound on a tree can expose it to pathogens and insects, leading to decay. Frass, which is often the excrement from wood-boring insects, is another sign that the tree may be infested and possibly decaying. Fruiting bodies, which can appear as mushrooms or other fungi growing on or around a tree, are often indicative of a fungal infection that can lead to internal decay.

Therefore, healthy bark stands out as not being a sign of decay, while the other options indicate potential issues that could harm the tree's health.