Control of the insects that prey on cucurbits can be difficult and requires a multipronged attack. Since nematodes are microscopic it is doubtful you can see them, but they can be part of the solution. Neem products, alone are not very effective controls of the adults, and most of the rest of the insecticides will also kill off the predators of these buggers.
Surround, a Kaolin clay spray, has been shown to be fairly protective.

Here is a link that might be useful: Cucurbit pest control

So I'm learning (about the neem oil). Thank you for the link, hopefully I can come up with a solution!

Neem is complicated, so keep reading up on it.

It acts as a repellent (antifeedant), first and foremost. It has very little "instant kill " effect, so you'll still see the adult pests flitting about but they won't feed on the treated plants to the same degree as untreated plants.

Insects have shown a reluctance to lay eggs on or in treated plants.

The third way that neem works is also unusual. It acts as a growth regulator to those insects that do feed on treated plants, affecting their ability to molt, and to reproduce.

SO! While it may appear that neem isn't working on adult insects, it really is. You just have to understand how. It's a useful tool in a healthy, strong IPM program.

I'm a big proponent of 'Surround' kaolin. It comes as a wettable powder that you mix with water to spray on the plants. But it shouldn't be applied to flowers. I apply to stems, foliage, and sometimes the fruit itself. It gets used on my veggie garden to protect against sun scald and heat stress...it makes a very big difference.

My garden arsenal includes a commercial insecticidal soap, Surround, Neem oil, and a horticultural oil of some kind.

This is also my first year growing cucumbers. I only have a few (~10 plants in a 5 ft row) so I hand pick adult cucumber beetles in the morning. I am especially happy when I kill mating couples in flowers, knowing not only did I kill two bugs, but hundreds of future bugs! LOL. There are still more beetles than the threshold for treatment. But I'll accept that if the plants can keep survive and producing for a month or so.