Department of Crop Science
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Item Identification of Maize Leaf Diseases Based On AlexNet and ResNet50 Convolutional Neural Networks(2023-08-30) Micheni, Maurice; Birithia, Rael; Mugambi, Cyrus; Too, Boaz; Kinyua, Margaret KMaize crop protection is crucial for global food security, requiring accurate disease identification. In Kenya, farmers rely on subjective visual analysis of symptomatic leaves, which is time-consuming and prone to errors. Computer vision technologies, like deep learning and machine learning, offer promising solutions for disease identification. This study applies Convolutional Neural Networks (CNNs), specifically AlexNet and ResNet-50, to automatically learn image features and enhance speed and accuracy in maize leaf disease identification. A dataset of 3200 digital maize leaf disease images from Embu County is used for training and testing. AlexNet achieved the highest average accuracy of 98.3%, followed by ResNet-50 at 96.6%. The machine learning, support vector machine (SVM) exhibited the lowest average accuracy of 85.5%. These findings highlight the significance of utilizing AlexNet and ResNet-50 in maize leaf disease identification and classification.Item Effect of Intercropping on Potato Bacterial Wilt Disease and Tuber Yield in Kenya(Karatina University, 2023-12-06) MUSAH, S.M.; Birithia, R.K.; Kamiri, H.W.; Kahariri, E.Potato (Solanum tuberosum L.) is a major tuber crop in Kenya, whose productivity is heavily impaired by bacterial wilt disease, caused by Ralstonia solanacearum (Smith). Existing management strategies have not been effective, owing to the diversity and robustness of the pathogen and variation in the host range. The objective of this study was to evaluate the effectiveness of intercropping on the incidence of bacterial wilt and yield of potato in Kenya. A field experiment was conducted in four potato-growing counties, namely; Nyandarua, Nakuru, Bomet and Bungoma in Kenya. Treatments included intercroping with spring onion (Allium fistulosum L.); garden pea (Pisum sativum L.); and cabbage (Brassica oleracea var. capitata L.). Treatments also included a pure stand of potato as the control. Generally, intercropping had a significant suppressive effect (P<0.05) on the incidence and severity of bacterial wilt disease. Intercropping potato with spring onion, in particular, had the highest disease suppressive effect, followed by intercropping potato with cabbage; and lastly by potato with garden pea. Accordingly, potato-onion intercrop recorded the highest potato tuber yield (12.9 t ha-1), while the potato pure stand recorded the lowest tuber yield (7.9 t ha-1). Bacterial wilt disease incidence positively correlated with disease severity (r = 0.931; P<0.05). In contrast, the disease incidence and severity negatively correlated with tuber yield. In terms of Land Equivalent Ratio (LER), the highest value (1.64) was with potato-onion intercrop; and the lowest (1.35) with the potato-garden pea intercrop.Item Control of Bacterial Wilt in Tomato Using Chitosan Intercalated with Tea Extracts.(OJS/PKP, 2022-04-21) Gatahi, Dennis; Kihurani, Agnes; Harrison, WanyikaIn this study, tea extracts were intercalated in chitosan gel to enhance the inhibitory effect of the complex on bacterial wilt in tomato. The disease caused by Ralstonia solanacearum can result in 100% crop loss under severe infection. Chitin was ground into powder of 0.1 mm size, deacetylated using concentrated NaOH solution and tea extracts from green, purple and black tea adsorbed through rotary evaporation. Confirmatory tests on effective adsorption were done using FTIR and XRD, while bioassay experiments were performed to determine efficacy of the chitosan intercalated with crude tea extracts (CICTE) on the pathogen and tomato growth. In vitro and In situ tests were carried out in growth chambers and greenhouse respectively. The greenhouse trials were conducted for a period of 2 years in three sites i.e. Gatundu, JKUAT and Makuyu. The bioassays demonstrated significant (p < 0.05) reduction of R. solanacearum turbidity marked by change of optical densities (OD) from 3.55 to 1.04. In addition, there was significant (p < 0.05) inhibition of the cultured R. solanacearum and reduced wilt incidence in tomato plants treated with CICTE and later inoculated with the pathogen. Tomato plants treated with CICTE also recorded a significantly (p < 0.05) higher yield compared to the control. The study therefore recommends utilization of CICTE as an effective and environmentally safe biopesticide for the devastating bacterial wilt pathogen.Item Management Strategies of Prosopis juliflora in Eastern Africa: What Works Where?(2024-04-22) Kamiri, Hellen Wangechi 1,2, *; Choge, Simon K. 3; Becker, Mathias 2Abstract: Prosopis juliflora is a shrub/tree originating from the Americas. Since its introduction for fuel wood afforestation into eastern Africa, it has been invading crop- and rangelands with negative effects on the environment and on livelihoods. Understanding the management strategies for Prosopis and matching them with ecological, social-cultural, and economic needs of the eastern African region is a pressing scientific issue. We analyzed management strategies of Prosopis, focusing on determinants and drivers of their choice of applied management strategies as well as their effectiveness. We identified 1917 scientific contributions published between 1970 and 2022. Following a multi-step screening, we reduced the references to 53 relevant (internationally) published papers with a focus on the management of Prosopis in the east African region. Analysis of the literature shows that factors driving invasion dynamics but also land users’ social-economic as well as cultural attributes determine the type of management strategy and shape local control actions. Main strategies comprise (1) physical containment of invasive spread, (2) chemical, mechanical and biological approaches to reduce stand densities, (3) complete eradication, (4) restoration of invaded land, and (5) economic use of Prosopis products. Adopted strategies are based on actual and perceived impacts of invasion, and the adoption and success of individual strategies is highly location specific.Item Home Sustainable Management of Invasive Pests in Africa Chapter Influence of Predatory Mites, Phytoseiulus longipes Evans. on the Within-Plant Diurnal Migration and Distribution of the Red Spider Mite, Tetranychus evansi, Baker and Pritchard on African Nightshade, Solanum scabrum(Springer, 2020-07-14) Kungu, Miriam; Subramanian, Sevgan; Salifu, Daisy; Fiaboe, Komi K. M.; Azandémè-Hounmalon, Ginette Y.; Gitonga, Linus; Onyambu, Gladys K.; Deletre, Emilie; Martin, ThibaudUnderstanding the within-plant diurnal migration and distribution of the Red spider mite, Tetranychus evansi Baker and Pritchard, in the presence of the predatory mite Phytoseiulus longipes Evans, on African nightshade, S. scabrum, is critical in developing an Integrated Pest Management (IPM) strategy for the pest. The T. evansi density, day and night cycles, and presence of P. longipes, on the within-plant migration and distribution of T. evansi on African nightshade were hence investigated. The results indicated that T. evansi does not exhibit a circadian migratory movement pattern on S. scabrum at lower densities (50 and 100 mites). However, T. evansi was observed to have a density-dependent collective displacement and distribution to the top of the plant, as densities increased (300 and 600 mites). The presence of P. longipes on the plant enhanced the within-plant migration of T. evansi, even at low densities (50 and 100 mites). However, there was no apparent pattern of migration and movement that was observed within the plant. The increased within-plant movement of T. evansi in presence of the predatory mites and collective displacement of T. evansi at higher densities indicate a potential for developing an IPM strategy using the acaricide treated net, which is discussed further.Item Leveraging Mobile Phones in Crop Pests and Disease Surveillance-Perspectives of Farmers in Kenya.(Corpus publishers, 2023) Ouma, Gordon Otieno; Awuor, Fredrick Mzee; Makiya, Cyprian Ratemo; Okanda, PaulAgriculture plays a crucial role in ensuring food security and employment in Kenya. However, farmers in the country have been struggling with low crop yields due to pests and diseases. To address this issue, mobile-based digital surveillance technologies have been recommended as potential solution. However, these technologies have not been widely adopted by farmers, prompting this study to investigate the reasons behind this and propose strategies to improve their uptake. This paper reports on the farmers perspectives in Homa Bay County, Kenya on the adoption of mobile phone based digital tools in crop pest and disease surveillance. The study employed quantitative approach, involving surveys with 326 selected farmers. The study identified several factors contributing to the low adoption, including lack of training and capacity building, limited technical support to the farmers, limited access to necessary infrastructure, and neglect of co-creation of these solutions with the farmers. Given these findings, it follows that these solutions are intentionally designed to be farmer-centric, and handholding provided to the farmers on use of these technologies including providing farmer training and capacity building.Item Spatio-temporal change of selected soil physico-chemical properties in grevillea-banana agroforestry systems.(Elsevier Ltd, 2023-09-18) Musongora, Muyisa; Karanja, Nancy; Kimenju, Wangai; Kamau, SolomonIn Africa, banana is mainly produced by small-scale farmers under complex production systems for both home consumption and income generation. Low soil fertility continually constraints its production and farmers are embarking on emerging technologies such as improved fallow, cover crops, integrated soil fertility management, agroforestry with fast growing tree species to address this challenge. This study aims at assessing the sustainability of grevillea-banana agroforestry systems by investigating the variability in their soil physico-chemical properties. Soil samples were collected in banana sole stands, Grevillea robusta sole stands and grevillea-banana intercrops in three agro-ecological zones during the dry and rainy seasons. Soil physico-chemical properties significantly differed among agro-ecological zones, cropping systems and between seasons. Soil moisture, total organic carbon (TOC), P, N, Mg decreased from the highland to the lowland zone, through the midland zone whereas soil pH, K and Ca showed the opposite trend. Soil bulk density, moisture, TOC, NH4+-N, K and Mg were significantly higher in the dry season compared to the rainy season but total N was higher in the rainy season. Intercropping banana with grevillea trees significantly decreased soil bulk density, TOC, K, Mg, Ca and P. Soils under banana sole stands accumulated higher potassium, magnesium, calcium, phosphorus with a higher soil bulk density and pH compared to grevillea-banana intercrops and grevillea sole stands. This suggests that intercropping banana and grevillea trees increases the competition for these nutrients and requires careful attention for the optimization of their interactive benefits.Item Crop Production in Irrigation Schemes in Turkana County, Kenya, Before and During COVID-19 (2018-2021)(2023-08-11) lLokuruka, Michael N. I.Turkana County, located in the northwest of Kenya, is an arid county and the poorest in the country, with a poverty index of 79.3% vs. 34.4% for the country. Due to its aridity, crop production is severely constrained and the County is a net importer of foodstuffs, except beef, mutton and camel meats. Crop production in the operating irrigation schemes depends on water from retreat flooding in March-May and any that is let into and retained in canals when the seasonal rivers are flowing. This project aimed to assess the influence of COVID-19 and other undetermined factors on crop production in 10 irrigation schemes along the Tirkwell River, over the period 2018-2021. The study administered a semi-structured questionnaire to 104 randomly selected farmers, who owned farm plots in the irrigation schemes. One-on-one interviews were held, due to the high level of illiteracy of the respondents. Twelve elders and administrators were the key informants. The study established that sorghum was the dominant crop grown in 9 out of the schemes, except in Kooliyoro-Kaaiteese, where maize was the main crop. Other crops in declining order by production volume included cowpeas, green grams, black grams and in Keekoroe-ngole, some green vegetables. The weight of the dominant crop and other crops varied significantly (p≤ 0.05) in the same irrigation scheme across the years of interest for this study, and also across the irrigation schemes over the production period. The results of the study showed that COVID-19 breakout did not affect crop production in the irrigation schemes studied. Farmer poverty level, lack of expert extension services, use of uncertified and reused seed, unreliable water supply, and regular droughts affected crop production. The most productive 3 schemes in descending order by crop production volumes were Nanyee, Napool andKeekoroe-ngole, while Naremit was the least productive. Crop production suffers from long-term sustainability in all the schemes for most of the above reasons. To improve crop production, the study recommends the provision of expert extension services, a steady water supply, annual donation of certified seeds, improvement in crop-care services, streamlining crop marketing services and the upgrade of governance and management capability in the irrigation schemes.Item Assessment of Production Constraints and Contribution of Avocado to Food Security and Income in the Mount Kenya Region, Kenya(2023) Kamotho, Grace N.; Asiko, Lydiah A.; Kibanyu, James K.; Kinyua, Phares R.; Karaya, Rebecca N.; Muthee, Patrick M.; Mwathi, Zipporah M.Avocado (Persea americana Mill.) belongs to the family Lauraceae and it is an important crop to rural communities and economies in Kenya. Currently, avocado is grown in several agro ecological zones mainly by small-scale growers (85%) who grow it for subsistence, local markets and export. About 70% of avocado is grown in Central and Eastern region of Kenya. Central region produces 40%, Eastern 28%, Western 13%, Rift Valley 10%, Nyanza 6%, Coast 2% and Nairobi County 1%. The main production areas are Muranga, Kiambu, Thika, Embu, Meru, Taita Hills and Kitale. The aim of this study was to assess the production constraints and contribution of avocado to food security and income in Mount Kenya region. The study population comprised of smallholder avocado farmers. Purposive sampling was done in selecting highest producing sub-counties of avocado in Nyeri, Muranga and Embu counties. Simple random sampling was used to select 40 smallholder farmers from each of the selected sub counties who participated in the survey. Data was collected using a structured questionnaire and analysed using SPSS computer package. Results indicated several constraints in the production of avocado including pests and diseases, lack of quality planting material, poor soils, lack of technical knowledge by avocado farmers and lack of well-structured marketing system. The study identified a gap in value addition of avocado in Kenya. It was also demonstrated that avocado contributes highly to household income and food security. The crop should therefore be accorded priority by policy makers and more research needs to be encouraged especially in the management of pests and diseases. Capacity building to avocado growers should be routinely carried out so as to avoid the many challenges that emanate from lack of technical knowledge. Intervention in value addition of avocado is an aspect that Kenyan county governments need to engage in by investing in cottage industries on avocado processing.Item Farmer knowledge, management practices and occurrence of tomato root knot nematodes in Kenya.(2023-08) Birithia, Rael K.; Kuria, D.K.Root-knot nematodes (RKNs) (Meloidogyne spp.) is a major constraint to tomato (Solanum lycopersicum L.) production in sub-Saharan Africa; yet there is low adoption of recommended nematode control measures in regions like east Africa due to inadequate farmer knowledge about the pest and associated diseases. The objective of this study was to assess farmers’ knowledge status, and intensity of damage of root-knot nematodes and their management practices in Kenya. A survey was conducted in Kenya, during February to August 2021; using a semi-structured questionnaire administered to 282 randomly selected household heads of actively growing tomato farmers, at two elevations in three counties. Most farmers (98.9%) could not identify the disease precisely. They mostly attributed its symptoms to moisture stress and nutrient deûciencies. Most farmers (63%) practiced mono-cropping; while only 4.3% of farmers amended soils with manure. Respondents preferred growing RKN susceptible tomato varieties, mainly Rio-Grande, Cal J, Onyx and Kilele FI. A total of 92% expressed willingness to shift to RKNs resistant varieties, if recommended varieties match their desirable characteristics. Majority of the respondents lacked knowledge on nematode characteristics and its associated disease control. A total of 37.9% of the respondents did not use control measures against the RKNs. There was high disease incidence, severity and galling index in the surveyed areas.