squash bugs, get a bernzomatic hand torch(type you use to sweat copper or a brulé torch would work too) and burn them and their eggs off. be diligent about it and you may triple your harvest. it helps to have all your squash growing on trellis and off the ground. I inspect mine 2-3 times a week. I check under each leaf and stem. the plants usually wilt a bit from the flame but are generally unfazed by being torched. on rare occasions the infestation was too much and I just cut off pieces and burned them.
seven dust with a squeeze bulb applicator takes care of the squash bugs, tomato caterpillars, ants, etc. I also have one with diatomaceous earth. this is also helpful to squirt some inside the hollow tubes of squash plants.
light applications of fungicides early when you see it. if that doesn't work, trim and/or burn the plants with it. as with any fungus, dampness and humidity helps it grow/spread, this means water directly and not over the leaves. as a last resort you could probably mix up a light copper acetate mixture which is used as a fungicide on treated lumber. just keep the solution under 3% and wash your produce well after harvest. also don't do this unless you know exactly what you're doing as it can kill your plants, poison your soil, and make you sick if you do it too close to harvest.
I have also heard that a 1/1 mix of water and vinegar can stop white mildew.
if chemicals aren't your thing, use some oils like mint and eucalyptus. spray around the plants not on the plants. the oils can close up stomata and suffocate your plant. a mist spray is more than enough. I usually do a mix of 1 gallon of water 1 teaspoon of oils(combined) and 1/3 cup of liquid Castile soap. this can help deter some insects and pests like squirrels, rabbits, deer, etc.
I have also had some success using predator urine to keep deer out. it works if you're vigilant, but wears off quickly. best way to stop the deer is to sit outside at night with a slingshot and clay shot tbh. after a couple weeks they'll not come back for a few months until they forget.