Yellow squash...what's the problem?

Hi!

Should I be at all concerned about these squash plants? This is my first year "gardening", so leaning on you all for knowledge. Ha!

I've attached a full shot of the plant, and a close up of the leaves.

FYI...I have not applied any pesticides/insecticides to this point. Should I? If so, what?

Thanks!

It looks like some kind of pest is chewing on your squash! They often leave little yellow marks when they bite on the leaves, and it will turn brown and decay a few days after that.
Check the undersides of the leaves for eggs (they'll be tiny and may be hard to spot at first) and look along the stems for signs of squash vine borers.
I dealt with SVBs a few years ago and didn't manage to get it in control; lost all my plants.

Sorry, I completely missed the second part of your question!

Neem oil was sugggested to me as a treatment for my bug problmes a few years ago, best sprayed on at night so the oils can soak in and not burn the plant in the sun.
If you do have Borers (look for "sawdust" like buildup towards the base of the stmems) you may have to do plant surgery to remove the larva from the inside. It probably seems drastic to slit the stems open and pull the bug out, but the alternative is that the whole plant dies. I'm crossing my fingers that it isn't borers and is instead some other wee little beastie that's bothering your squash!