Why are my bottle gourd leaves curling?

Bottle gourd leaf curl has several causes. Aphid colonies under leaves cause curling and sticky residue — spray neem oil + soap solution. Mosaic virus (transmitted by aphids) causes mosaic yellowing with curl — remove affected plants, no cure. Heat stress causes temporary wilting curl that recovers after evening watering. Check under leaves first: if you see insects or sticky residue, pest control is the fix; if not, assess watering frequency.