The answer to 'when to treat for silverfish' is that the best time to treat for silverfish is when you first notice their presence in your home. Silverfish are nocturnal insects that feed on carbohydrates, starches, and sugars, and they can be a common pest in many homes.
The ideal time to treat for silverfish is as soon as you spot them, as they can reproduce quickly and cause damage to fabrics, books, photos, and other household items. Catching an infestation early is key, as it is much easier to control and eliminate a small population of silverfish than a large one that has had time to spread throughout your home.