The problem could be do to several things. Two that are most common are bacterial wilt and squash vine borer. Bacterial wilt results when cucumber beetles feed on the plant. The water conducting tissues become clogged and the plants wilt and die. To control the beetle, you can do one of several things. Using floating row covers on top of the plants from seeding until they begin to flower prevents the beetles from feeding. But the covers must be removed once flowering begins so the bees can pollinate. Also, there are several insecticides such as carbaryl, acetamiprid, cyfluthrin, and permethrin that can be used. Treatment begins just as the seedlings emerge. Follow the directions on the label. The other common problem is squash vine borer. The adult beetle lays eggs at the base of the vine. The eggs hatch out and bore into the vines. If left unchecked, the vines die usually about the time they begin to fruit. To control the borer, the vines can be sprayed with carbaryl, permethrin, or cyfluthrin (these are chemical names - they are sold under various trade names). Treat the stems on the young plants. The row cover also works for this insect as well, preventing it from laying the eggs. It's extremely important that you follow crop rotation and not plant any member of the squash family in the same location for every 3 years. For squash vine borer, you can plant butternut versus acorn as it is less susceptible.
