Masters Graduands September 2023

Tomato in Kenya is the second important vegetable both in production and revenue generation. In recent times, its production and yield has adversely been affected by the newly introduced invasive, tomato leaf miner (Tuta absoluta). A survey to determine farmer pest management practices and strategies was conducted by interviewing one hundred tomato small scale growers. The study established that tomatoes are mainly grown by men (75%). Rio grande and Cal J were the common varieties grown Tuta absoluta was considered the most important pest o associated high yield loss at 40% for tomatoes.

Breeding has significantly improved drought tolerance in green gram. Important pests of green gram are pod borers, aphids and whiteflies. Field experiments were conducted in southeastern Kenya to evaluate a collection of old and new green gram varieties for tolerance to field pests, and to identify traits that confer resistance. The old varieties were KS20 and N26, both released in 1990s whereas the modern counterparts were Biashara, Karembo and Ndengu-Tosha.

Bacterial wilt (Bw) caused by Ralstonia solanacearum (RS) is a major production constraint in tomato causing yield losses of 35% to 90% in field and greenhouse. The objectives were; to determine reaction of common tomato varieties; assess the effect of watering regimes on Bw in the greenhouse and effect of irrigation systems on incidence and severity of tomato varieties. Eighteen varieties were screened against RS, experiment was laid out in RCBD with 3 replications. Second experiment was laid out in CRD with 3 varieties subjected to 50% field capacity (FC), 100%FC and 120%FC.

Green gram (Vigna radiate (L) is among the most widely consumed legumes in Kenya. Root rot of green grams caused by Fusarium oxysporum has been documented as the major biotic challenge during the production of the legume crop. It causes a loss between 10-100% in green gram yields. Chemical and cultural practices used in root rot management have several limitations including high cost, harmful effects to the environment, hazard to human and animal health.

Maize is cultivated in different climatic and ecological conditions in Africa. In Kenya, it’s a principal crop with an average of 90% of residents in maize production areas relying on it for food and employment. Production of maize has been on decline due to infection by Maize lethal necrosis (MLN) disease that triggered by infestation of MCMV and potyvirus, mainly Sugarcane mosaic virus (SCMV). Transmission of MCMV and SCMV through seed and soil may occur though at very low rate.

Soil-dwelling insect pests constitute a significant challenge to vegetable production in Kenya, but their monitoring and management is constrained by soil heterogeneity and overreliance on pesticide. A field survey was conducted to assess the occurrence and management of soil-borne pests of cabbage and onions in the major growing counties and the insects were collected for morphological and molecular characterization.

The overreliance and the use of broad-spectrum synthetic insecticides have been used in the management of pests affecting French beans has been linked to the detrimental effects on non-target organisms and human health. This has led to a growing interest in alternative pest management methods, such as the use of plant extracts which have minimal effects on beneficial insects and are safer for the environment.

Maize is the staple food for most Kenyan households, however over the decade maize yields have decreased or remained stagnant. This is partly attributed to poor soil fertility and soil heterogeneity, despite much work having been done to tackle soil fertility issues. To investigate this, 23 soil samples (0 to 30 cm) were collected from 13 counties in Kenya and a nutrient omission trial was set up in the greenhouse at the Kenya Agricultural and Livestock Research Organization (KALRO) Kabete.

Stinkbug is an important pest of macadamia. The study was to establish infestation density and qualitative loss attributed to stinkbug, farmer management practices of the pest and to rear the egg parasitoid in the laboratory. Farmer knowledge on stinkbug and its management practices were assessed using a structured questionnaire administered to 384 randomly selected macadamia farmers in Kiambu, Embu, Nyeri, Meru and Murang’a counties in a survey.

Aluminium toxicity limits production of sorghum in soils with pH<5.0. It restricts root elongation lowering the absorption of water and nutrients, eventually, plant growth and yield are affected. Liming, a most adopted remedy against Al toxicity proves costly and unsustainable, however, deployment of tolerant genotypes could sustainably aid in management of the constraint. Magnavaca solution screening was used in phenotypic evaluation of selected lines for Al tolerance.