Browsing by Author "Irungu, L."
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Item Effect of Agro-Ecological Zones on Predacious Mites (Acari: Phytoseiidae) and Pest Mite Eutetranychus africanus (Acari: Tetranychidae) Populations in Citrus Orchards of Kenya(Persian Journal of Acarology, 2022-07-15) Kiptoo, J.J.; Mutisya, D.L.; Ndegwa, P.N.; Irungu, L.; Godfrey, R.; Oduor, G.R.; Kiptoo, G.J.; University of Nairobi ; Kenya Agricultural and Livestock Research Organization ; Machakos University ; Masinde Muliro University of Science & Technology ; CABI ; Egerton UniversityPhytoseiidae mites' survival and reproduction depend on optimal environmental factors. A total of five different agroecological zones (AEZs) were surveyed twice each year from 2017 to 2019 in Kenya. In Eastern Kenya sample farms were small scale citrus orchards in the counties of Machakos [Low Midlands-Four (LM4)] and Makueni [Upper Midlands-Three (LM3)]. In the Coastal Lowlands-Four (CL4) similar small-scale citrus plots were sampled in Kwale, while in the highland Rift Valley region sample sites were ADC-Suam orchards of Kitale of the Lower Highlands-Two (LH2), where the large-scale farms were under citrus crop culture. The fifth site sampled was Baringo area of the Low Midlands-Five (LM5) where small plot citrus crop dominated the sample sites. Out of 68 fields of repeat surveys, 40% of citrus plots yielded varied diversity of phytoseiid mites. The major pest from the sites was citrus brown mite, Eutetranychus africanus. In this study, population fluctuation of phytoseiid mites was observed under different climatic conditions of temperature, relative humidity, dew-point and citrus plant age (in years). On the major pest E. africanus, three factors were evaluated for correlation and significance to infestation levels on the citrus crop. Of the three evaluated factors of temperature, citrus tree age and phytoseiid density in the orchards, temperature parameter did not significantly influence the pest mite (E. africanus) infestation levels for all combined AEZs factors. In the present case studies of specific AEZs, older trees led to higher pest mite density while low phytoseiid numbers correlated inversely to higher E. africanus infestation levels on the citrus trees. The information here could be used proactively to plan for management of E. africanus as the major pest in citrus orchards in specific agro-ecological zones.Item Influence of Soil Types on Citrus Nematode Species Diversity and Abundance Under Varied Ecological Conditions in Kenya(Pakistan Journal of Nematology, 2022-05-21) Kiptoo, J.; Mutisya, D.; Ndegwa, P.; Amata, R.; Irungu, L.; Godfrey, R.; University of Nairobi ; Kenya Agricultural and Livestock Research Organization ; Machakos University ; Masinde Muliro University of Science and TechnologyPlant-parasitic nematodes (PPNs) cause major crop losses by damaging plant roots and causing reduced absorption of soil nutrient elements. A two-year survey in 2018 and 2019 was conducted in most citrus growing regions in Kenya to assess the abundance, distribution and diversity of plant parasitic nematodes from different soil rhizosphere. Nematode population in 200cc of soil and 5g of roots were collected for PPNs extraction by using modified Baermann’s technique and identification by morphological features. The findings indicated that four major genera were abundant in different citrus growing ecological zones in Kenya. The identified species were Meloidogyne incognita, Tylenchulus semipenetrans, Helicotylenchus dihystera and, Pratylenchus brachyurus. The most abundant species in all the surveyed localities was T. semipenetrans. Factor regression analysis results showed that modest rainfall amounts favoured high density populations of PPNs on citrus roots where soil types of Rackers in Baringo and Luvisols, Ferralsols and Cambisols in Machakos County were dominant. Tylenchulus, Meloidogyne and Helicotylenchus species were most abundant in Kitale, Taita-Taveta, Kilifi and Kwale. The results presented here show how possible population density of PPNs in varied soil class types, rainfall amounts and prevailing temperature would be influenced by abiotic factors therein.
