If a vine borer killed it, the Sevin is useless. If a fusarium wilt (Sudden squash death) killed it, your Sevin is useless. If the Sevin allowed it to live, chances are there'd be few bees left around to pollinate it.

To check for Fusarium solani f. sp. cucurbitae:

"Fusarium crown and foot rot of squash and pumpkin is caused by Fusarium solani f. sp. cucurbitae. The first symptom is wilting of the leaves. Within several days, the entire plant may wilt and die. If the soil is removed from around the base of the plant, a very distinct necrotic rot of the crown and upper portion of the taproot can be seen. The rot develops first as a light-colored, water-soaked area which becomes progressively darker. It begins in the cortex of the root, causes cortex tissue to slough off, and eventually destroys all of the tissue except the fibrous vascular strands. Infected plants break off easily about 2-4 cm below the soil line. The fungus generally is limited to the crown area of the plant."

tj