Yes, it is too late to fertilize. But the better question is do you really need to? Trees established in the landscape seldom ever require fertilization. The only sure way to determine if your trees need it is if they are showing weak or off color growth or if you have a soil test done to determine any deficiencies. It is very unlikely the pines require it.

Also, fertilizer spikes are a huge waste of time and money. Probably the most inefficient way of fertilizing plants ever devised. If you determine you do need to fertilize, a granular type fertilizer spread throughout the dripline (not concentrated in a single spot) is a much better approach.