Poor Fruit Set - Cucurbits
Pollination depends on bees. 8-20 bee visits per flower in commercial fields is suggested to be adequate for good pollination. It is recommended that at least 1 beehive per acre is necessary to achieve the required number of visits. Hives should be brought into the field when both the male and female flowers are set.
In cucurbits, there are more male than female flowers and the ratio can be 15-18 males to 1 female flower. (Male flowers are on a "stalk" that is the same width from the stem to the flower. Female flowers have a bulge in the stem just under the flower. See 3rd photo.) This may worry some growers when seeing so many blossoms but few or no fruits developing at the onset of flowering. Irrigating the fields with overhead irrigation during the daytime stops the bees from visiting the flowers and may lead to poor pollination. Some researchers have shown that extended periods of night temperatures above 80 F tend to favor development of more male flowers than female flowers in some pumpkin varieties. This has led to fewer pumpkin fruits during the years when higher temperatures occur during flowering period.