Essentially the squash bugs look like crosses between little spiders and stink-bugs. Their sole purpose is to nibble, slowly, on the larger squash leaves until they wilt and die. Then they move on to the next squash leaf. They have no intention of killing the plant, rather they like it for its nutrients so they play a game of keeping it alive while still using it for food. Quite a "nice" parasitic relationship if I've ever heard one. However, the borer, which often accompanies the squash bug because it just follows their scent and let's them do all the work (read: lazy), burrows into the base of the plant and eats it from the inside out until the plant stem becomes hollowed and the plant dies.
The borer looks like a little lot like a grub and a little like a caterpillar. They actually will cocoon over the winter and start the process again next year unless an insecticide is used and a good rototilling is provided, to disturb their winter slumber. Dead give-aways of its presence include a sawdust-like substance at the base of the plant, a discoloration (often brown or tan) at the stem down to the roots and wilted leaves. Damn things. I guess I know what I'll be doing next year--planting them all separately and spraying them once in a while to prevent this from happening again.
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