Spray only where needed. The product should also be labeled for spiders or nuisance pests. There are many approaches used by various companies. Spiders seek warmth and shelter in protected places like logs, under piles of rocks, bark and other debris. The wood pile is a choice winter residence.
Many spiders ride inside on the firewood.
Protect outside wood piles with covering. The more debris that falls on the wood, the more attractive the spiders find it. It isn't advisable to spray the wood pile. Pesticides with enough residual to keep spiders out could be toxic to handle, ant there is no information available on possible health effects of burning wood treated with pesticides. This material is picked up on the insects' body and eaten when the insect grooms itself.