My ridge gourd plants have lot of male flowers and good amount of female flowers which are turning into fruits about 1.5 inches. But after that the fruits are turning yellow and then drying off. What could be the reason.
Provided the plant is otherwise healthy and vigorous, it could be that either the plant is too young (does not have enough foliage yet) or that pollination has failed. Gourds and squashes frequently provide their own male and female flowers on different parts of the plant so insect activity is required to move the pollen from one to the other. The male flowers need to be producing active pollen and the females need to be receptive; this can fail when the plant is too dry, or the weather is too hot or too cold or rainy, or simply because the insect population is not dense enough to visit all the flowers.
Provided the vines are producing lots of flowers of both types continuously, eventually all the stars will line up and you should start getting fruits forming.