Why can treated poles with high internal moisture content decay internally?

• A. Because checks deepen exposing untreated wood
• B. Because preservatives kill fungi
• C. Because moisture evaporates
• D. Because the wood becomes harder

Answer: (A)

When moisture is high inside a pole, cracks called checks can form and grow deeper into the wood. Those deeper checks reach inner wood that the preservative may not have penetrated or protected as effectively. Once the interior wood is exposed, fungi in the moist environment can invade and decay it from the inside, even though the surface appears treated. The preservative mainly guards the outer layers, but a deepening crack creates a pathway for decay to start internally.

Preservatives killing fungi isn’t the problem here—killing fungi would help prevent decay. Moisture evaporating would reduce the problem rather than cause internal decay. And making the wood harder doesn’t drive decay.