Hello and thank you for using the Ask an Expert website. Yellow jackets are a fact of life for us here in the Northwest especially this time of year.  When they choose to nest near where humans often visit or garden they become pests.  Remember that yellow jackets are predators and as such kill lots of other insects that are also considered pests.  Kill all the yellow jackets and you inherit their job.  There are several types of wasps that are called yellow jackets some are scavengers that are attracted to meats and others are attracted to sugars, what they are feeding on changes with the seasons.  Also recognize that yellow jackets food supply is dwindling as the season progresses so they invade more of our space looking for food.  The reason they no longer accept your bait could be that they switched to other foods that are in greater supply as the season progresses.  Wash out your trap dump out the dead and dying yellow jackets and re-bait.  Yellow jackets do not eat rotting meat so you need to replace meat baits frequently.  Purchase fresh chemical bait and use it.  When yellow jackets are digging holes into my apples it is my first clue to check the apples for ripeness.  They seem to know when things are ripe before I do.  Harvest those grapes and apples that are attracting them (after checking for ripeness).  Pick up windfalls and dispose of them where the yellow jackets will not be able to access the food.  I have included a link to a University of California at Davis article that should help give you better understanding of your foe.  http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7450.html  Finally here is another link that will help you round out your approach to yellow jacket control this one from Oregon State Extension.  http://extension.oregonstate.edu/gardening/node/467