I would guess that it just increases the radius of afflicted mosquitoes.
If you clear out all stagnant water, it seems possible that some of the mosquitoes within flying range of you will go find alternative water sources that are further away from you but still within flying range. But if you redirect some fraction of these mosquitoes to a bad water source, you’ve ensured that those mosquitoes effectively don’t breed at all. And OP suggests in another comment that this strategy is also useful to cull seasonal mosquito breeding, which seems to come in one distinct wave each year; if that’s the case, shrinking the size of the initial population growth should have a pretty big impact. The impact would also be proportionate to the degree to which mosquitos are capable of longer-distance migration; if they don’t move at all, the bucket seems pointless, but if they’re capable of moving more than a few miles, the bucket would also be helpful in catching stragglers from other regions.
(A cursory Google search seems to suggest that mosquito breeding cycles are year-round in the tropics but seasonal in more temperate climates. But also this information comes from a Reddit thread, so take it with a grain of salt.)
I would guess that it just increases the radius of afflicted mosquitoes.
If you clear out all stagnant water, it seems possible that some of the mosquitoes within flying range of you will go find alternative water sources that are further away from you but still within flying range. But if you redirect some fraction of these mosquitoes to a bad water source, you’ve ensured that those mosquitoes effectively don’t breed at all. And OP suggests in another comment that this strategy is also useful to cull seasonal mosquito breeding, which seems to come in one distinct wave each year; if that’s the case, shrinking the size of the initial population growth should have a pretty big impact. The impact would also be proportionate to the degree to which mosquitos are capable of longer-distance migration; if they don’t move at all, the bucket seems pointless, but if they’re capable of moving more than a few miles, the bucket would also be helpful in catching stragglers from other regions.
(A cursory Google search seems to suggest that mosquito breeding cycles are year-round in the tropics but seasonal in more temperate climates. But also this information comes from a Reddit thread, so take it with a grain of salt.)