Hello everyone. I planted some zucchinis a couple of months ago, they grew well and each plant had 2 big healthy zucchinis. But then the plants started getting sick. I think they got powdery mildew. Right now they look almost dead, and haven't sprouted flowers for three weeks. The stems seem sick and rotting, and the leaves are very dry and white and are being eaten by bugs.

I live in Costa Rica where it rains pretty much everyday and is very humid. We get rain all afternoon, everyday.
So I think it is a combination of weather, powdery mildew, squash borer damage.
I also spotted a bug around the plants today.
Anyone knows how to fix this? Are my plants done? If so, the next time I plant zucchinis how should I prepare?

Before the plants got this sick, I tried using a mix of sodium bicarbonate, dish soap and water to spray the leaves. I did it for a week but didn't seem to kill the powdery mildew.

Here are some pictures:

http://mygardenyote.blogspot.com/2013/06/dying-zucchini-plants.html