Just as I picked our first cuk, after a relatively pest free spring, we are blessed with both spotted and striped beetles. Only a few so far, but I know I'll be watching the cucumbers and squash very closely. The beetles spread bacterial wilt quick as lightning.
The spotted beetles larvae live in the soil and eat plant roots. They are called Southern Corn Rootworms. But they dont just eat corn. They feed on plant roots and bore into germinating seed, large roots, and underground stems. This damage may result in wilting and stunting of plants or plant death.
I lost a whole row of spinach one year. I had a severe cucumber beetle infestation, the previous year, and I kept noticing that the spinach plants were sitting on top of the ground, they didn't have any roots...then I got a bunch of insect info from the extension agency and...I realized what a huge problem they really are.
I actually found that info in some paperwork I got from the Ag agency. I didn't realize their life cycle either. The Ag agent told me that Cucumber Beetles were a nuisance pest, and not much to worry about.. Then I read the paperwork and thought "What the. ? ". Like you said they spread diseases too. I just found that out recently, no I have 0 tolerance, for them.