**7. Pollination**

Flowers of commercial strawberry cultivars are hermaphrodite and self-fertile. However, self-pollination through gravity and wind is often partial since the pollen might drop on many, but not necessarily all of the pistils [28, 29]. The fertilized ovules, through auxin release, promote receptacle development and formation of fleshy tissue [30]. However, non-fertilized ovules fail to develop, resulting in fruit deformations that raise the proportion of non-marketable produce [31]. In addition, there is a relationship between the number of fertilized ovules (achenes) and berry weight [30, 32]. Insects, mostly honeybees (*Apis mellifera* L.) serve as complementary pollinators of strawberry [33–35]. Nonetheless, beehives in the recent years have been facing the severe worldwide problem of the colony collapse disorder [36], which has significantly decreased the beehives availability for pollination, and consequently brought about a dramatic rise of the rental prices [37]. Additionally, honey bees foraging is temperature-limited [38, 39] and hence, pollination performance sharply declines under high day temperature during fall, as well as under low winter temperatures. Indeed, greenhouse strawberry crops often suffer from inadequate flower fertilization, so alternative insect pollinators that replace or act together with honeybees seemed reasonable.

Bumble bees (*Bombus terrestris* L.) have several attributes that are beneficial for pollination [40, 41]. Therefore, bumble bees have been introduced and have successfully replaced honey bees as pollinators of greenhouse vegetable [41] and orchard crops [38, 42–44]. Today, *B. terrestris'* colonies are a "ready-made shelf product", easily

**Figure 7.** *A bumble foraging on a strawberry flower. (Photograph by O. Guy.)*

*Winter Strawberries Production in Greenhouse Soilless Culture under an Arid Climate… DOI: http://dx.doi.org/10.5772/intechopen.104390*

suitable for marketing and transport to any given greenhouse or habitat [41]. The efficiency of bumble bees as a greenhouse-strawberry pollinator was found comparable to that of honey bees [45, 46]. In greenhouse-strawberries in Israel, *B. terrestris* displays considerable advantages compared to honeybees, particularly in respect of foraging under harsh weather conditions (**Figure 7**).
