Some vegetables require cross-pollination by insects before any fruits are formed. Other vegetables, while not requiring bees for pollination, will produce better yields if insects are present. It is not necessary to have bees present on any of the leafy vegetables since a fruit is not desired. Yields of bell pepper and eggplant may be improved by bees. Beans and tomatoes are self-pollinating, and bees are not required for fruit to form.
Home gardeners should avoid spraying and dusting insecticides when bees are present. If an insecticide is used, try to avoid concentrating the insecticide in the blooms. On some vegetables it may be possible to avoid spraying the blooms altogether.
Cucumbers and all of their relatives, gherkin, pumpkin, casaba, crenshaw, honeydew, cantaloupe, watermelon, pumpkins and all types of squash and gourds require cross-pollination by bees or other insects for fruit to develop since separate male and female blooms are produced on the same plant. Conditions unfavorable for insect activity can reduce fruit set. Male blooms appear a few days before the female blooms are seen. During unfavorable conditions the male bloom will abort before the female bloom is pollinated. This condition usually corrects itself when weather conditions change from cool to warm weather and conditions for bee flights improve.
A common complaint of home gardeners is that various vegetables produce blooms which fall off and do not produce fruit. High rates of nitrogen fertilizer applied too early in the season can cause blooms to abort. Bloom drop is a fairly common occurrence during periods of cool weather (below 55 degrees F at night) and high rainfall. These conditions are also not favorable for bee activity, and pollination by insects is reduced. Some garden centers sell products which claim to help plants hold the blooms, but these products cannot always eliminate bloom drop during unfavorable weather.
Okra blooms not pollinated by insects must depend on self-pollination. When humidity is high, okra pollen is sticky and does not shake off easily. If okra blooms are not pollinated the same day they open, the bloom will fall off without producing an okra pod.