Some think none is best, other fertilize daily with manure tea. Everybody agrees that fertilizing after August encourages leaf growth when the gourd should be hardening. Few pests bother hardshells. Snails and cucumber beetle larvae can kill seedlings. Adult cucumber beetles chew holes in leaves, but more important, carry bacterial wilt.
Squash bugs are often abundant.
Vine borers don't seem to bother hardshells. The remedy is harvest when the gourd is mature. When the vine begins to turn brown where it meets the gourd, cut the vine two or three inches from the gourd. You can wash with either chlorine bleach or borax solutions. Handle gourds gently to prevent bruising, and put in a warm, airy place.