Start with the soil.
What is that soils pH?
What are the nutrient levels? Are they in balance?
What does the soil smell like?
What kind of life is in that soil?
How much organic matter is in that soil?

I have an 8x4 raised garden. ... I lost my cucumbers and squash and my tomatoes quickly followed

==>> you are severely overplanted ...

i have seen squash .. one plant.. cover 10 sq feet ... a tomato.. 3 sq ft if not caged and tended

perhaps a pic would change my mind ...

in overplanting.. you are affecting many variables .. such as sunlight on plant... sun on soil causing water management issues ... and reducing air movement complicating disease issues ...

with so many issue perhaps out of kilter... i am loathe .. to think you have a clinic/bug/disease problem ...

we often find with newbs.. that they want to attack the EFFECT ... while not considering the CAUSE ...

and i think the CAUSE of your problems is the over planting ... rather than the EFFECT .. which is the resultant problems you are finding .. solving the EFFECT .. does not address the CAUSES

a term for you to research.. would be SQUARE FOOT GARDENING ... wherein there is all kind of theory as to how to maximize a given space ... while addressing the issues i mention ... and go figure.. i just checked.. there is a forum named such ... who knows how active it is ...

soooo... whether you cant live w/o a squash ... the issue would be.. if you really need to grow it .... though you might be better off.. using the space for more manageable plants.. always consider.. what a harvest costs in season .. and i was just talking to ma.. and she said they are nearly giving away such at the market ... so one would ask themselves.. do i really need to strangle my space.. for a veg that costs near nothing in prime season ...

i recall a readers digest joke.. that said.. the only time they lock their cars in newport RI ... was in zucchini seasons.. for fear that strangers will leave bags of such in your car.. if you dont.. lol ... and for me.. that kinda sums up ... the gourd/zuki season ... when in season.. they are giving them away .... why should i bother growing them ....

good luck

ken

As kimmsr said, start with the soil. Add plenty of organic matter to help with the overall soil health. It's possible that many of your diseases are coming from soil. That said, the next step is to mulch around your plants. This prevents diseases from splashing up from the soil (since you are concerned its "in the dirt") onto your plants. I've found this especially true for tomatoes. Also be sure to rotate crops.

With the proliferation of pests you have, floating row covers may help. Also, planting parsley as a scapegoat plant (I don't know if anyone actually calls them that, but you get the idea) should help. Parsley should attract good insects and absorb some of the bad ones, and you won't notice the damage as much.

In my opinion, you should try to plant some vegetables that aren't fruits, like greens, or alliums (which aren't normally too bad pest-wise). The variety should give individual species of insects less to go after.

Matt

And always move your plants around from season to season....that's called "crop rotation" and it limits the chances of diseases like blight to recur year after year. 8x4 is not a huge area to play with but you can at least move tomatoes and squashes from corner to corner. And don't worry about those plants overcrowding. Squashes and other cucurbits can be planted at the edge of a raised bed or even in containers with the vines allowed to sprawl at will. And tomatoes should be staked to grow more or less vertically for best flower and fruit production.

The row cover is also an excellent idea. Start when your plants are still very young - just seedlings. That's when most of the flying nasties are out and about laying the eggs that turn into the plant devouring larvae.

Sigh...I feel your pain

I am having the same problem.
I have a 10 x 18 garden, with so many pests I started ripping things out. I also have 4 earth boxes and containers. I worked so hard and bugs are winning. I managed to keep beautiful squash plants from SVB under covers, I did find some in the beginning stages and avidly plucked eggs after uncovering for vacation purposes. So, I consider my war with them, won! Now my problem is beetles and mildew.

I planted all but one disease resistant squash, and every kind has powdery mildew.
I had my plants under cover from SVBs until going on vacation-removed them and then all hell broke loose. It seems the row covers saved my plants from PM and SVB. The plants were huge and beautiful.
My cucumbers have downy mildew AND cucumber beetles! These things came out of nowhere!! SO SO SO many. Just in the past week. They are chomping everything. I thought these beasts were spring bugs?
My tomatoes have blight, past the point of saving, but they have a ton of tomatoes on them, I'll just let them ripen and yank em out.
I grow gorgeous eggplant every year, this year, I think they may have got too much water (rain plus the auto watering system while on vacation). I do have some growing, but no more flowers. So I am planning my fall crop, but now am afraid of cucumber beetle larvae destroying my soil for next year.
The only thing I used was neem oil.

Another key to home gardening is daily patrol and hand removal of destructive pests and diseased leaves and other plant parts. This takes some research to learn what's bad and what's beneficial.

Squash is prone to failure and is abundantly available, so why take up all that space?

You can plant all kinds of greens...kale, chard, dill, bok choy, lettuces, etc. Plant garlic cloves in fall, peas, etc.

Even experienced gardeners lose crops due to nature.