You can use a hot-pepper spray that will repel rabbits, but you must keep applying it. Other choices are odor repellents like blood meal or fox-urine powder, all available at your garden center and online. Do not use mtohballs--these are poisonous and not meant for outdoor use. The best defense is a 30-foot tall chicken wire (poultry mesh) fence--perhaps you can fit it around the perimeter. The very best defense? Planting evergreens and other shrubs that rabbits won't eat, like American holly (Ilex opaca), juniper, pine, spruce and wintercreeper (Euonymous fortunei).