Improved Pollination Efficiency and Reduced Honey Bee Colony Decline in Greenhouses by Allowing Access to the Outside During Part of the Day

Abstract

Although honey bees are efficient pollinators of many crops cultivated in greenhouses, it is difficult to maintain colony strength and consequently pollination efficiency. Many bees die under greenhouse conditions and the colonies rapidly weaken. We examined the effect of adaptations to the hive entrance that allowed control of whether and when bees had access to the outside environment to see how it would affect pollination efficiency and colony condition in greenhouses with flowering cucumber (Cucumis sativus) plants in comparison with colonies that remained constantly inside the greenhouse, previously left in a dark environment or not. We recorded the type and period of visitation to the cucumber flowers, numbers of honey bees entering and leaving the two entrance hives and the effect of this type of management on the quantity of brood and food. Fiveframe Langstroth “nucleus” colonies were equipped with two 30 square centimeter entrances and two 3.0 cm diameter circular openings. Allowing the bees to make visits outside the greenhouse in early morning with redirection of bees into the greenhouse at 8.30 a.m. did not reduce visitation to cucumber flowers in the greenhouse. Maintaining colonies in the greenhouse reduced brood area and food stores. These losses were significantly reduced in colonies that had access outside the greenhouse during the early morning. Another advantage of alternating access to the inside and the outside of the greenhouse was that there was less possibility of interactions between bees and people working on the crop, and also pesticides application could be made without directly affecting foraging bees.

Impact of Natural and Hand-Assisted Pollination on Cucumber Fruit and Seed Yield

“…The high number of honeybees observed on cucumber flowers in the Open for foraging insects' treatment (Figure 2) suggests that open pollination allows honeybees free access to pollinate, whereas no honeybees was found in the Caged with insect-proof net treatment, which is consistent with other studies (Inam et al, 2015;Nicodemo et al, 2018). As a result of no special control measures used for the different treatments, the number of ants observed on cucumber flowers was not significant (Figure 3), indicating that ants are more interested in feeding on the excreted sap generated by aphids.…”

“…Also, due to the insect-proof net, which limited pollination, the assimilate produced as a consequence of photosynthesis was primarily employed for the vigour with a bias towards reproductive development. The high number of open male flowers in the Open foraging insects' treatment Table 1 is consistent with no obstacles to inhibit insect interactions with flowers promoting higher flower development as compared to other treatments (Nicodemo et al, 2018;Tuo et al, 2019). The low frequency of aborted female flowers in cucumbers treated with manual pollination highlights the need for alternate pollination methods (Nicodemo, Malheiros, De Jong, & Nogueira Couto, 2013).…”

“…The number of cucumber leaves did not change across treatments, which might be explained by the fact that all treatments received blanket fertilization. The high vine length in Caged with insect-proof net treatment Table 1 is likely owing to no insect disturbance to cause infections that may slow development (Nicodemo, Malheiros, De Jong, & Couto, 2018;Tuo et al, 2019). Also, due to the insect-proof net, which limited pollination, the assimilate produced as a consequence of photosynthesis was primarily employed for the vigour with a bias towards reproductive development.…”

A Hive Entrance System That Directs Honey Bees Inside or Outside a Greenhouse Reduced Colony Decline While Effectively Pollinating Zucchini Squash

“…In comparison with open-field production, one of the few disadvantages of greenhouse cultivation is the absence of biotic pollinators when plants that depend on these pollinating agents are cultivated in such environments. Introducing bee colonies into these systems can enhance fruit set and improve fruit quality [3][4][5][6][7].…”

“…However, confined bee colonies rapidly decline in a few weeks [3]. A strategy that can mitigate the impact on the bees allows bees to enter the greenhouse according to the pollination needs of the crop, and direct them to the outside to forage on natural food sources during the rest of the day [4]. This is also useful when bees in the greenhouse could interfere with other activities, such as pruning, harvesting, and pest control activities.…”