At one time there was some thought that DE was not too effective once wet but that seems to have been replaced of late. I would water as necessary and watch to see if the DE did loose effectiveness.

Not exactly 'of late', kimmsr. Glad you finally came around, though.

Moisture can alter the effectiveness temporarily, but as soon as the DE dries out, it will be back to normal. Even when soaked, it never completely loses its physical attributes.

Of course, watering or rainfall can wash the DE from plant surfaces.

DE is not on my list of pesticides to broadcast on outdoor garden areas since it is indiscriminate in what kinds of critters it can harm. Just about any arthropod is a likely victim in your garden. That will include bees, and the large number of predatory and parasitic species busy at work day and night both on the plants and in the soil....busy at work for US.

I do keep DE handy for use in our garage, which seems to be quite the gathering place for black widow spiders and common house centipedes.