Friday, 20 November 2020 08:01

Diversity and Abundance of Invertebrate Taxa in Smallholder Farms in Nakuru County: Effect of Dolichos-Based Cropping System and Field Margin Vegetation

Written by J. N. Obanyi1, 2, J. O. Ogendo2*, R. M.S. Mulwa2, J. G. Nyaanga2, E. K. Cheruiyot2 and P. K. Bett3
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J. N. Obanyi1, 2, J. O. Ogendo2*, R. M.S. Mulwa2, J. G. Nyaanga2, E. K. Cheruiyot2

and P. K. Bett3

1Kenya Agricultural and Livestock Research Organization, KALRO Njoro, Nakuru, Kenya

2Department of Crops, Horticulture and Soils, Egerton University, P.O. Box 536-20115,

3Department of Biological Sciences, Egerton University, P.O. Box 536-20115 Egerton, Kenya

*Corresponding Author: jogendo@egerton.ac.ke

 

Biological control by use of natural enemies is an emerging eco-friendly pest management method which can provide a sustainable alternative option of controlling pest. However, the conservation of these natural enemies within agricultural production systems is a challenge. Field studies were conducted in smallholder farms in Nakuru County to determine the effect of field margin vegetation in supporting the diversity and abundance of invertebrate taxa. Two cropping systems, dolichos monocrop and maize-dolichos intercrop, were planted in farmers’ fields with or without field margin vegetation in Njoro and Rongai sub-counties of Nakuru County during the long rains of 2019 and 2020. The treatments were arranged in randomized complete block design (RCBD) with eight (8) replicates per locality. The abundance and diversity of field margin vegetation in each farm, was determined by throwing a 1 m2 quadrat thrice per field margin and counting all plant species present and converting them to percent abundance.  Invertebrate taxa were trapped using yellow sticky cards, pan traps and sweep netting three times during the cropping season. Trappings were grouped, counted and morphologically identified using taxonomic keys. All data on counts were transformed using square root transformation (√X+ 0.5) before being subjected to analysis of variance using PROC GLM in SAS software and treatment means separated using Tukey’s HSD test at P≤0.05. Results showed that there were a total of eighteen (18) perennial species; 8 in Njoro and 10 in Rongai. There were more weeds species in Rongai (17%) compared to Njoro (14%) and more perennial weeds (21%) compared to annual weeds (13%). Mean abundance of invertebrate taxa was higher in Rongai (7.2) farms compared to Njoro (6.8) farms. Across the two environments the invertebrate taxa collected were composed of pests and their natural enemies and other insects like flies. The results further showed that invertebrate taxa were significantly higher in the Dolichos monocrop (3.6) than in the maize-dolichos intercrop (2.2). These results show that inclusion of field margin vegetation around smallholder farms enhances the conservation of diverse invertebrate taxa which is an important functional mechanism of managing different pests in integrated pest management.

Keywords: biological control, conservation, invertebrate taxa, natural enemies, plant diversity

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