Here’s the reason: Generally, bottle guard is cross pollinated cucurbit crops. Honey bees and other insects play an important role in pollination. If these kinds of insects are negligible in your field, the problem may occur. For the solution, some farmers collect the male flowers and tapping on the female flowers mechanically (by hands). It’s a very easy to identify the male or female flowers. Male flowers appear first on the vine. Female flowers will have the small gourd shape below the bloom, while males do not have.