Experts and BHG readers answer.
When pumpkins (Cucurbita) or summer squash (Cucurbita) slowly wilt to death, the culprits are usually squash vine borers-the larvae of a large moth that lays its eggs on the stems, usually near the base of the plant. The eggs hatch and the larvae bore inside and feed on the interior of the stems. By the time you see sawdustlike frass (excrement) coming out of the holes, substantial damage has been done. There are three ways to prevent serious borer damage.Cover plants with floating row covers until they begin to blossom. The row cover will protect the plants from borers, squash bugs, and other pests.Arm yourself with beneficial nematodes. Inject small amounts (less than a teaspoon) of these microscopic critters into the base of the plants' hollow stems every 4-6 inches; nematodes quickly kill the vine borers. You can buy a garden syringe for this purpose. Inject the stems with Bt (Bacillus thuringiensis), as described in the previous paragraph. You may also be able to save the plant by slitting the stem lengthwise near the frass, digging out the borer, and covering up the base of the stem with moist soil.