Control of termites and land use effects on their Diversity in Machakos and Embu Counties, Kenya
Kanyi, Nahashon Chege
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GENERAL ABSTRACT Termites cause damage to agricultural crops, forests and natural vegetation, in several parts of Africa. In Eastern Kenya, termites have been reported to cause between 50 to 100% yield losses in maize agro-ecosystems. General soil microfauna diversity analyses have been done in Eastern region of Kenya but there is little information documented on diversity and distribution of termites. Understanding the diversity of termites allows implementation of appropriate management strategies and application of species-specific control methods. Bio-control agents and cultural methods such as intercrops have been reported to control termites, but there are no studies that document the comparative efficacy of these control methods in maize agro-ecosystems in Eastern Kenya. This study therefore aimed at determining the termite species diversity in Machakos and Embu sub-counties. The effects of soil properties on diversity of functional groups of termites, efficacy of various biological control agents of termites and effect of intercropping maize with legumes and sorghum on infestation levels of termites and damage of maize in Eastern region of Kenya were also evaluated. Three different habitats comprising of maize crop farms, maize intercropped with beans and natural vegetation were purposively sampled in Machakos and Embu counties. From these habitats, termites were sampled for diversity analyses. Soil samples were also taken from these sections and their physico-chemical properties analyzed to determine their effects on functional diversity of termites. To determine the effect of maize intercrops on infestation levels of termites, maize was intercropped with soybeans, field beans and sorghum in different plots measuring 10m x 10m with maize mono crop as a control. The experiment was carried out in Yatta sub-county in Machakos county and it was laid out in a completely randomized block design with each treatment replicated four times. The level of termite infestation was determined during two seasons. Termites were sampled from 30cm x 30cm quadrats laid at an interval of 5m along the transect. Additionally, five plants from each plot were also randomly selected for assessment of termites’ infestation. Effect of bio-control agents was determined by treating Macrotermes subhyalinus and Odontotermes badius with biocontrol agents under laboratory conditions. There were five treatments replicated four times. The treatments were Azadirachta indica, Metarhizium anisopliae, ants predating on termites (Megaponera analis and Dorylus gribodoi), termidor (fipronil 9.1%) and distilled water as control. Termite diversity in Machakos and Embu counties was assessed by Renyi diversity analysis. Analysis of variance using R Software was used to compare the efficacy of various biological control methods and the effect of intercropping maize on infestation levels of termites. The relationship between termite functional diversity and soil properties was assessed using Canonical correspondence analysis. Trinervitermes gratiosus was only found in Machakos county and occurred in significantly greater numbers in natural vegetation macrohabitat compared to other macrohabitats. The abundance of termite species and functional groups varied between seasons and macrohabitats. Group II and IV were positively correlated to sand and silt, respectively while group IIf was negatively associated with sand. There was a low percentage of lodged plants in maize-sorghum intercrop which also had low population densities of M. herus and Odontotermes badius in both seasons. In the bio-control experiment, the mean percentage mortality caused by M. anisopliae in both O. badius and M. subhyalinus were significantly lower compared to the rest of the treatments. The information obtained from this study can be used in designing integrated termite control strategies.