There are little black bugs slowly eating away my Arugula. I live in Denver CO. The weird thing is, we have a pot of Arugula ~50ft away from where the other Arugula is planted and it's completely fine. The plants are watered using micro-sprinklers twice a day. The soil was mixed with compost from a local ranch (horse manure).
My only hypothesis is the weeds growing in the planting area (crab grass and purslane, which we are struggling to keep up with) are somehow attracting the bugs.
Any ideas on what we can do to eliminate these bugs?