What is recommended for mildew and sapstain?
See Wood Care Treatments as well as Stain Additives.

When do I apply a borate based wood preservative like PeneTreat or Tim-bor?
PeneTreat (Tim-bor) is recommended to be applied before applying any exterior finish. If a sapstain control was applied first, check product information here. PeneTreat (Tim-bor) can be applied at any time on logs or lumber as long as there is not an existing coating on them. PeneTreat (Tim-bor) can be applied one log at a time or after the structure has been erected. If a wood conditioner is being applied at the same time, apply PeneTreat (Tim-bor) first. They can be applied using a garden sprayer with a fan tip.

Is PeneTreat or Tim-bor hazardous to humans?
No, PeneTreat (Tim-bor) is not hazardous once applied to wood, but in powder and liquid form it is harmful to humans, domestic pets, fish, and wildlife. See product label for safe handling procedures.

I have tiny holes in my logs with sawdust on the ground. What is this from?
See Are You Bugged?

I have some rotted logs; what do I do?
There are several treatments for rotted logs. For prevention of further rot, use the Bor8 Rod (Impel Rod) or the CobraRod. These are borate based rods that come in different sizes. The rod size will depend on the diameter of the log for equal diffusion. When the moisture content of the wood is 20% or higher, rods will activate and diffuse preservatives into the wood preventing rot and decay from starting. On average, one rod will diffuse one cubic foot.

PeneTreat (Tim-bor), as mentioned earlier, LiquidWood and/or WoodEpox can be used. Liquid Wood is just that; liquid. When brushed on or poured into the wood, it will harden and strengthen the wood. WoodEpox is an epoxy in paste form that can be used to mold the rotted space to a "new" log. WoodEpox can be tinted. (Tinting to match the stain color is recommended before applying a finish; you only need to tint the surface layer.) 

Will Bug Juice or PeneTreat change the color of my stain?
Neither of these products will affect the color of any stain, but Bug Juice will significantly affect the clarity and gloss of Lifeline Advance Topcoat.