For many years we’ve avoided selling seedless grapes because they are very susceptible to a devastating disease, Black Rot (caused by the fungus Guignardia bidwellii), that is nearly impossible to control using standard organic fungicides. We recently read about a quite simple way to control black rot – using paper bags to prevent fungal spores from ever landing on and infecting the developing grapes. So we are giving seedless grapes another shot – both in our garden and for sale in the nursery. Grapes do not need sunlight to develop properly so bagging has no affect on their ripening. It has the additional benefit of protecting ripe grapes from marauding wasps. It’s a bit of work to protect each grape cluster with a bag, and the bags may need replacing once over the course of the summer, but the rewards are well worth the effort. Bag grape clusters immediately after bloom. You may need to tear slits in the top of each bag to avoid damaging the cluster stem. Staple or paper clip the bag closed.