DE is rather indiscriminate so it is best not to use on plants that are ready to become or are in bloom as it will kill bees, butterflies and and other pollinators. It does wash off but remains as effective on the ground as it does on the leaves. You should apply when you know the hatch/life cycles of the problem insects but not when there are blooms. I would use a puffer. I am going to be coating my entire yard with it this fall to hopefully eradicate the lily beetle population and again on the early spring. While it is not toxic you do want to avoid breathing it in so adhere to the precautions. It should also work on many of the jumpers and the like too.