We're under attack!

by cucumber beetles.
Our poor cucurbits (cucurbitaceae-the gourd family which includes our cucumbers, zucchini, pumpkins and melons) are swarmed by yellow-and-black-striped bad news.

We tried to protect the plants and give them a head start by sheltering them with floating row covers  (Reemay and Agribon) which allow sunlight and water through but keep insects out. However, these also keep out pollinators, so when plants start to flower, we have to remove the covers. Another factor which forced us to remove the covers was weed pressure. 
We planted our zucchini maybe a few days or a week before we planted the cucumber, but it has definitely made a difference. Our zucchini are hardy and producing lots of yummy fruit, but the cucumbers did not grow as quickly, and have not yet flowered, and are suffering much more damage.
We were worried about losing the entire crop, and considered our options. We don't like to use sprays, but there are a few natural, certified organic pesticides which can be used in certain circumstances. We didn't want to take any chances with insecticides near open flowers where our honey bees could be affected, but because our cucumbers were so decimated and still haven't budded, Jay sprayed pyrethrum early one morning, and since we have much fewer beetles on our cukes. Pyrethrum is derived from chrysanthemums, and is sprayed on the leaves, which then poisons the bugs which ingests it. There were other interventions we considered, such as a dust-on powder which is actually sharp enough to lacerate insects, and a clay coat which would protect the leaves, but also slow photosynthesis. We also thought about trying to purchase the natural predators of cucumber beetles.
On our other plants, we have noticed that some are definitely hit harder than others, which supports the theory that insects attack weaker plants, which can tell us more about which varieties are hardier and which soils are more developed. Jay also found a site which claimed that a plant can suffer up to 50% leaf loss and still produce a full crop.
So, the infestation freaked us out and had us squishing lots of bugs . . . but bugs are part of garden environment, and the best way to keep our plants safe is to give them good soil and keep the bugs off them as long as possible. And given our large beetle population, hopefully the natural predators will show up on their own!
and on an even more positive note, the japanese beetles are harmlessly distracted by our asparagus jungle, largely leaving our raspberries alone :)
I guess the moral of the story is that in gardening, like in health care, prevention is the best medicine. But proper nutrients, such as compost, will grow stronger plants, rather than pesticides eventually creating stronger bugs!