Many strains of mosaic viruses infect cucurbits. In Arkansas and in the southern states, certain watermelon strains of a mosaic virus have caused extensive losses of fruits of zucchini and other summer squash, cucumber and pumpkin because of the occurrence of mosaic-patterned, yellow and green, knobby fruits. Plants of cucurbits may become infected at any growth stage. Pollination Poor pollination and fruit set can cause low yields. Watermelon has male and female flowers.
Male flowers produce the pollen, and the female flowers produce the watermelon fruits.
Honeybees and other bees transfer the pollen. After the plant produces many male flowers, every seventh flower on a plant branch is female. All male and most female flowers drop off the plant, and fruits set more or less irregularly throughout the season. The condition of the plant and number of melons already set determine the number of female flowers that set fruit later. Therefore, pruning misshapen melons while small is essential to encourage additional fruit set.