I've heard similar worms can affect any root crop. My bulb onions are planted in another raised bed, I'm curious to see how they will look when I pull them up. My carrots are definitely slower growing than I thought they would be...I sure hope they aren't affected. I was planning on planting some garlic this fall...I'll keep in mind to keep it out of the bed with the worms.
One thing I read is that those worms are worse if you have too much compost that hasn't 'composted' enough, or conversely, sandy soil lacking in nutrients. My dad filled my raised beds with pure compost from a local landscaping company, so I wonder if it wasn't composted enough. There were quite a few pieces of wood in it. He initially told me it was a soil/compost mix so I didn't do anything to amend it. I have some black dirt that I would've added had I known.
I'm impressed with your watermelon. I live too far north to grow 99% of melons. I keep scouring the seed catalogs for 'super duper extra early' watermelons, but all they have are early cantaloupes. It doesn't matter - I don't have enough garden space anyway.
hope you get some rain soon. It's hot and dry here so I'll be out watering today too.