Virtual Graduation Ceremony

45th Graduation Ceremony

PhD in NATURAL RESOURCES MANAGEMENT


Effects of Pests and Diseases Associated with Flowering Phenology on Seed Quality of the Red Pod Terminalia (Terminalia Brownii Fresen 1837) in Selected Drylands of Kenya

Abstract: The Red pod terminalia (Terminalia brownii Fresen (1837)) is an important multipurpose tree species growing in Arid and Semi-arid lands (ASALs) of Eastern Africa. Despite its wide utility in construction, wood carving, and medicine and in the cottage industry, its seedlings and products such as timber and posts are not available in the required quantities. Scarcity of its seedlings has affected afforestation and conservation activities in ASALs. Flowering and fruiting patterns of T. brownii and the effect of predation by insect pests, diseases on seed viability and their interrelationships are not well understood. The study investigated: insect pest infestations and the stage at which they infested flowers and fruits, fungal diseases that infested flowers and fruits, distribution and effects of female and male flowers on seed quality and the relationships between seed quality and infestation by pests and diseases. The study was carried out at Nduumoni, Kimose and Kendu Bay in Kitui, Baringo, and Homa Bay counties respectively. A combination of descriptive and experimental designs was adopted with a Randomized Complete Block Design. Twenty reproductively mature trees were randomly sampled at each study site and tagged for the assessment of insect pests and fungal diseases at three crown levels. In each sampled tree, tertiary branches were further tagged at flower-bud initiation; flower buds, full bloom, immature and mature fruits were sampled at each crown level for the identification of insect pests, and fungal diseases across three study sites. There were no significant differences in the mean number of defoliators of Lepidoptera 9.03±1.01), Coleoptera 4.6±0.63) and Diptera 11.2±0.78 across sites. Seeds inoculated with Botryosphaeria, Fusarium, Alternaria and Pestalotia recorded germination means of 9.03±3.17, 22.06±1.42, 62.46±8.13 and 69.51±11.16 respectively, while the control recorded a germination of 96.76±1.62. There were significant (p ≤ 0.05) relationship between bisexual and male flowers, the spearman correlation coefficient was (0.5). There were also significant (p ≤ 0.05) relationship between mature and immature fruits, the spearman’s rho correlation co-efficient of (r = 0.5). Approximately 80%, 65% and 30% of the bisexual flowers, fruit set and immature fruits translated into fruit set, immature and mature fruits respectively (n=90). The probit model predicted the probability of getting quality (viable) seeds was 0.673, low-quality seeds 0.103, and empty fruits 0.0016. Pests and diseases significantly reduce T. brownii seed quality, therefore, fruits and seeds should be dressed with appropriate insecticides and fungicides to reduce infestation. This information can be used to improve production, handling and supply of quality T. brownii seeds and seedlings for woodlot establishment.

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