The Flower, Pollination and Fertilization
The courgette/zucchini (Cucurbita pepo) bears both male and female flowers on the same plant. The flowers have 5 sepals and 5 yellow petals.
•Male flowers generally outnumber female ones by 3.5:1 to 10:1. The male flowers appear a few days before the female flowers.
•Each male flower is located at the end of a slender stem. It has 3 anthers.
•Each female flower is located at the end of a short stalk and possesses a thick style and a three-lobed stigma. The swollen ovary is located at the base of the corolla and is divided into 3-5 sections.
•Male flowers produce nectar and pollen whereas female flowers produce only nectar. The latter produce more nectar than the male flowers, thus attracting more bees compared to male flowers.
•The flowers open early in the morning and close around noonof the same day, never to reopen.  

•Because the plants have separate male and female flowers, some agent, usually bees, is necessary to transfer pollen from male to female flowers. The pollen grains are large. The shape and weight of the fruit are affected by the amount of pollen on the stigma. •Because pollen viability drops rapidly, it is important for a female flower to be pollinated as early as possible on the day it opens, while the pollen is still viable. 
•A single visit by a honeybee to the female flower does not necessarily bring about a proper fruit-set, since the honeybee can reach the nectaries without touching the stigma.
•In contrast, the bumblebee, due to its size, comes in contact with the stigma at the same time as it gathers nectar.
•Bumblebee workers pick up pollen on their body hairs when visiting the male flowers.
•The foragers lose large quantities of pollen (large and sticky grains) while processing it to pollen loads on their hind legs. As a result, the bumblebees do not succeed in gathering sufficient pollen for their brood.
•Therefore, in order to assist the normal development of the colony, it is necessary to add 1 teaspoon of dry pollen daily. 

The hive
•Because the courgette flower has abundant nectar, the bumblebee hive is provided with enough sugar water to last just for the delivery trip.
•The amount of nectar in the crop is sufficient to support normal development of the colony.
•When it leaves the factory, the standard colony for courgette consists of the founder queen, a few dozen workers, pupae, larvae and eggs.
•The hive does not contain males. This is a strong colony with an anticipated life expectancy of 5-10 weeks.

Introduction scheme
•The optimal introduction range is 5-10 hives per ha.
•The hives should be placed upon appearance of first flowers.

Field advisory service
•The first visual indicator of the bumblebee’s visit on a female flower is pollen grains scattered on the stigmas.
•In the male flower the anthers’ lobes are partially empty of pollen.
•Follow-up of the activity of the bumblebees should take place early in the morning. It includes three components:
1) Observation of entries and exits of worker bees to and from the hive.
2) Observation of bee visits to the female flowers.
3) Checking fruit-set: In a female flower that failed to set fruit, the ovary becomes yellow and eventually rots and drops off, whereas in a flower that set fruit successfully, a normal fruit develops in a state of full turgor, and with a light green color.