The answer to 'when to treat for wasp' is that the best time to treat for wasps is in the spring and early summer, before their nests are fully established. This is when the queen wasp is just starting to build the nest and the colony is small. Treating early can help prevent the nest from growing larger and becoming more difficult to control later in the season.
Wasps are most active and aggressive in the late summer and fall when their colonies are at their largest. Treating a nest during this time can be more challenging and may require professional pest control services. It's important to be cautious around wasp nests, as their stings can be painful and dangerous, especially for those with allergies.