Speaker
Description
Agroecosystems harbor diverse communities of pollinating insects that provide ecosystem services, improving the quantity and quality of crops. Basic knowledge is still needed about the importance, role, diversity, and abundance of these insects in many Moroccan crops. In order to study the importance of wild pollinator communities for apple production, an economically valuable entomophilous crop in Morocco, it is essential to understand the basic pollination needs of the main varieties to promote their production. The main objectives of this study were to assess the dependence of three apple cultivars (Golden, Gala, and Delicious) on insect pollination and then to evaluate the pollination deficit resulting from the absence of these pollinators. To do this, we used 1 mm² fine-mesh bags around the branches of apple trees to compare fruit set and yield with pollinator exclusion, open, and open + manually pollinated flowers. The results revealed variable rates of fruit pollination success for the three varieties tested and for the three pollination treatments. The Gala variety showed the highest pollination success rate, reaching a value of 74.99% (control group), followed by Golden (61.3%), and finally Delicious (29.26%). The effect of insect pollinators on apple pollination success, assessed by initial fruit set, revealed that the exclusion treatment led to a reduction in pollination success in all varieties compared with the control group. This reduction contributed to an initial fruit set loss of around 62.01%, 45.26% and 13.9%, respectively, for Gala, Golden, and Delicious. However, statistical analysis based on the Mann-Whitney U test revealed a very highly significant difference in pollination success between the two treatments for Gala (Z= -4.264, p-value = 0.000) and 28 Golden (Z = -4.240 and p-value = 0.000). On the other hand, the Delicious variety showed no significant difference between the two treatments (Z = -1.801, p-value = 0.072).
In the second part of our work, we investigate the potential of apple crops in Al Haouz to host a wide diversity of solitary bees. We sampled insects in two orchards separated by a 5 km distance. We focused our comparative analyses on solitary bees, as they are known to be the most efficient group of pollinating insects. We recorded a total of 2807 individuals (Diptera, Hymenoptera, Coleoptera, and Lepidoptera) from 17 field trips and three sampling methods: two active and one passive. Among this diversity, we collected 1,379 solitary bees (49.13%) divided into 6 families and 22 genera. 187 solitary bees were observed directly on apple blossoms. Four genera (Andrena, Lasioglossum, Heriades and Eucera) accounted for 58%, 14%, 10% and 5% of the total abundance of solitary bees visiting the apple crop. The results of this study underline the important role of insect pollinators for apple crops and the urgent need to implement sustainable strategies to preserve pollinators, and particularly solitary bees, in agroecosystems.
Keywords: Solitary bees, diversity, abundance, pollination, apple trees, fruit set.
