No, Snapshot can only be used on non-bearing plants. We do carry Fertilome Over the Top Grass Killer that can be used in your vegetable garden (please read the product label to be sure your vegetable are listed on the label).
Since every part of the country is different, we recommend calling your local county extension office for proper application times in your area. They will know exactly when you should apply a pre-emergent for best results.
We would recommend Snapshot 2.5 TG as the product label specifically lists daylilies as a tolerant species to the product.
In general you will use 2.3 - 4.6 lbs. per 1000 sq. ft. First you should determine which usage rate is needed for your use by reading the product label.
Here is how to determine what spreader setting is needed for your spreader:
If you need to use 3lbs of product per 1,000 sq ft you would add 3 lb of product to spreader, start with a medium setting, then apply product to a 20 x 50 ft area (1,000 sq ft). If you have product left, your setting is too low. If you run out of product, your setting is too high. Typically if you walk at a normal pace and set the spreader at the middle setting, that is usually the right amount per 1000 square feet.