Its most likely a disease. It can't be cabbage worms or your cabbages would have them too! Just try treating them for diseases like you would with a cabbage since they are strongly related to cabbages, also, pick them young. overgrown kohlrabi tastes woody and just plain weird. so, pick them when the stems reach about an inch or so in diameter and keep that up until they are 2-3 inches in diameter.
Last edited by thepatrick; Jul 16th, 2007 at 12:00 AM.