Suitability of Hedgerow Planting System in Managing Bee (Hymenoptera: Apoidae) Pollinators in Farmlands of Kenya
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Date
2016
Authors
Guantai, Mary Mwari
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
Bee presence in the farmland is crucial for provision of essential crop pollination
service. However, this is highly determined by the availability of forage resources
and nesting sites among others. Therefore, the overall aim of this study was to
determine suitability of hedgerows in providing bee needs in Kenya. Specifically,
the study was carried out to determine i) bee nest presence in farmlands bordering
Mt. Kenya, Mt. Kilimambogo and Kakamega forests, ii) the floral richness of
hedgerow plants in farmland bordering NW Mt. Kenya forest, and iii) diversity
and abundance of bees visiting hedgerows in farmlands bordering NW Mt. Kenya
forest. The data were collected through i) excavation and characterization of
solitary bee nests along a transect from fields near the forest to fields 15 km away,
ii) observation of floral resources for period of 1 year (September 2013 to August
2014) along a transect from fields near the forest to fields 15 km away and ii)
observation of bees visiting flowers of hedgerow plants for period of 1 year along
a transect from fields near the forest to fields 15 km away. Their presence on
hedgerow plants was compared with those present on cropped area and uncropped
patches in the field. The number of bee nests was statistically (P<O.OOI)higher in
fields far from the forest implying that forests provide essential nesting sites for
farms close to the forest. Kakamega and Kilimambogo farmlands had higher
number of bee species recorded showing that farm practices are friendlier to bees
in those sites. Hedgerow plants hosted most of the bee nests indicating that if
properly managed they can be used to manage bee presence in the farmland. Nests
for large bees e.g., Xylocopa spp. were located on the house rafters, indicating that
hedgerow plants could not offer better sites for these bees unless concerted efforts
are put in place to include large bee nest sites. There was high diversity and
density of flowers across the year in the hedgerow plants indicating that bee forage
needs can be sustained in the farmland. The most important bee forage plants were
Aspilia mossambicensis and Plectranthus barbatus, which were recorded in all the
farmlands. Sixteen bee species belonging to three families (Apidae, Halictidae and
Megachilidae) were recorded. The species richness curve showed a possible
presence of more species in the farmland. This indicates that proper management
of bee food and nests can increase their density. Honey bees (Apis mellifera) were
the most abundant as expected a priori due to their sheer number and
domestication. However, with proper bee management, the density of other bees
such as carpenter bees can be enhanced. It is suggested that an integrated
hedgerow management that includes keeping plants with yellow, purple, white and
pink flowers and inflorescence (particularly those belong to family Asteraceae and
Lamiaceae) as well as including dead wood for large bees be implemented to
enhance solitary bee presence in the farmland. This should be implemented in an
area-wide approach to provide connectivity within the farmland and natural
habitats for food resources, nesting sites and refugia of bees.
Description
Thesis Submitted in Fulfillment of the Requirements for the Award of the Degree of Doctor of Philosophy in Agricultural Entomology in the School of Pure and Applied Sciences of Kenyatta University