| dc.description.abstract | Avocado is a valued fruit in the Kenyan horticultural industry for local and export
market and it contributes about 17% of the horticulture's foreign exchange earnings in
Kenya. In spite of this, diseases and poor quality fruits limit access of Kenyan avocado to
export market as well as reducing on the profitability of the crop to farmers.
The current study was conducted to establish the agronomic and handling practices
in avocado production so as to identify those processes influencing post-harvest losses. A
questionnaire was used to conduct a survey in three avocado producing districts; Ernbu,
Muranga South and Kiambu and 60 farmers, 12 bulk traders and 2 processors were
randomly selected as respondents. Laboratory investigations were done to establish the
pathogenic factors contributing to post-harvest losses in avocado. During the survey five
mature diseased fruit samples were collected from every farm for identification of
pathogens responsible for postharvest losses.
Anthracnose is considered the most important disease contributing to post-harvest
losses in avocado. Four commonly grown avocado cultivars; Fuerte, Pinkerton, Hass and
Puebla were evaluated for their susceptibility to Colletotrichum gloeosporioides.
Susceptibility was assessed through surface necrosis (SN) diameter, lesion depth (LD) and
compound aggressiveness index (CAI). The susceptible cultivar Fuerte was used to
evaluate the efficacy of three fungicides (Iprodione, Fenhexamid, Thiophanate methyl) and
hot water as post-harvest management strategies for anthracnose.
Results of the study indicated that post-harvest losses are contributed by improper
management of avocado trees and poor post-harvest handling of fruits. In brief, pre-harvest
pest and disease control, pruning, methods of harvesting and handling are improperly done.
There were also significant differences in spraying practices and farmer-training status
amongst districts surveyed.
Colletotrichum gloeosporioides was the most frequently isolated post-harvest
pathogen (53.3%) followed by Fusarium spp (16.4%) with significant (P<O.OI) association
between pathogen incidence and locality. Other pathogens were Cladosporium spp (9.0
%), Penicillium spp (8.6%), Botrysphaeria spp (8.5%), Pestalotiopsis spp and (2.2 %)
Rhizopus spp (2.2%). The pathogens were isolated from both body and stem end rots.
All the four avocado cultivars tested were susceptible to anthracnose. Fruit maturity
did not affect susceptibility but there were significant (P<0.05) differences in their
susceptibility. Cultivar 'Fuerte ' was the most susceptible. Strong positive correlations
were revealed between lesion diameter (Surface Necrosis) and lesion depth in cultivars;
Pinkerton (R2 = 0.660), Fuerte (R2 = 0.554) and Puebla (R2 = 0.599). There was a weak
correlation in cv Hass (R2
= 0.242).
Thiophanate methyl significantly (P<O.O1) reduced disease progression when
compared to the other three fungicides tested and hot water, with the lowest mean Surface
Necrosis (SN), Lesion Diameter (LD) and Complex Aggressiveness Index (CAI). It
was evident that there was need to train farmers on all aspects of avocado production and
post-harvest handling. Further studies on post-harvest management of anthracnose in
avocado are necessary. In addition further comparative studies with different cultivars,
varying chemical concentrations and hot water at varying temperatures as well as postharvest
disease management under controlled atmosphere are necessary. Studies aimed at
establishing effects of cultivar and temperature on post-harvest disease management is also
required. | en |
