Pollination
As with all other members of the family, the flowers come in pollen-bearing male form, and the ovary-bearing female form, with both forms being present on the plant. Squash has historically been pollinated by the native North American squash bee Peponapis pruinosa, and related species, but this bee and its relatives have declined, probably due to pesticide sensitivity, and most commercial plantings are pollinated by European honey bees today. One hive per acre (4,000 m² per hive) is recommended by the US Department of Agriculture. Gardeners with a shortage of bees often have to hand pollinate. Giant squash grown competitively are usually hand pollinated. Flowers are kept closed before and after pollination to prevent cross pollination. Inadequately pollinated female squash flowers will usually start growing, but abort before full development. Many gardeners blame various fungal diseases for the aborted fruit, but the fix proves to be better pollination, not fungicide.
Read more about this topic: Squash (plant)