There are many squash varieties that have shown resistence to Powdery Mildew although none that will not develop it if conditions are present that encourage PM to grow. The link below will provide a list of varieties UNH has found to be resistant. All of these have demonstrated that resistance through natural genetic modification not via labs inserting strange genes into the plants DNA.
If squashes, or other plants do get Powdery Mildew I have had good results controlling it simply by spraying a 50/50 mixture of fat free milk and water every 5 to 7 days or a mixture of 1 teaspoon of baking soda per quart of water sprayed on the same schedule.

Here is a link that might be useful: PM Resistant Squash

Thank You. I picked up a few packs of organic squash seeds made by olds today, but I don't see them on the list.

I tried to water from the bottom, and they had lots of direct sun last year, yet the mildew seemed to go everywhere. I didn't try the milk thing, but will keep that in mind if I have a problem this year.

I am going to look online for some of the resistant varieties that were listed in the page you sent.

Thanks again;
Jamie

Organic/conventional is not the same thing as GMO/non-GMO. There are seed sources that are non-GMO that are nonetheless not organically produced seed.

I've never found a variety of spaghetti squash that could withstand squash vine borers or mildew. I grow a variety of pumpkin/squash called Long Island Cheese (or jarradahl) which is an old heirloom (not hybrid). Seed is widely available from the usual suspects -- Johnny's, Pine Tree etc. -- and most of those suppliers have both organic and conventional seed available. It is absolutely impervious in my experience to SVB. While it will get a bit of late season mildew, that never slows production down. The fruit is excellent -- sweet, dense orange flesh -- with very good keeping qualities. It's pretty much the only winter squash I grow anymore because it's just so reliably pest and disease resistent and productive.

Thank you for the information and seed suggestions.
Jamie