Etiology, Epidemiology and Management of Dieback Disease of Passion Fruit (Passiflora spp ) in Central and Eastern Regions, Kenya
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Date
2013-10-15
Authors
Wangari, Wangungu Carolyne
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Abstract
Passion fruit is important in Kenya for nutrition and income. Current
production is low and this is largely due to pests and diseases. In Kenya, major
passion diseases include Fusarium wilt, Phytophthora canker, Brown spot,
Woodiness virus and Dieback. Dieback causes over 80% of tota! produce loss
and has negatively affected the passion fruit value chain. The objective of this
study was to identify dieback pathogens, determine their aggressiveness,
investigate its epidemiology and identify effective management measures. A
survey was. carried out in major passion fruit growing areas in Central and
Eastern Kenya. Three research sites were set up in the study areas and 1 at
Kenyatta University, where epidemiological and disease management trials
were done. Passion fruit varieties assessed were Passiflora edulis var Sims and
KPF 12 hybrid. Diseased samples were collected for isolation and
identification of pathogens in the laboratory. Pathogenicity tests determined
aggression of the isolates. Data on disease severity were collected using a
dieback scoring chart (with a scale of 1 to 5, subjected to analysis of variance
and means separated by LSD at P = 0.05 using the Tukey's test. Results
showed that dieback is a disease complex caused by multiple pathogens
(Genus Fusarium, Phytophthora, Alternaria and Ascochyta). Disease was
most severe when pathogens were inoculated in combinations of 3 and 4.
Proper field maintenance practices reduced disease incidence and severity
(12% and 1.6 respectively) in Meru B while poor maintenance yielded high
levels (55% and 4.0 respectively) in Mathioya. Agronomic practices important
in transmission of dieback pathogens on the purple variety were pruning,
grafting and wounding (P :::;0.05). Mavuno and TSP fertilizers boosted plant
growth leading to lower disease scores of 2.2 and 2.3, respectively, as
compared to the control (2.92). None of the fungicides evaluated was curative.
Plants treated with Ridomil MZ had a low severity score (2.1), while those
treated with Milraz had a higher score (2.7). Water stress increased severity
thereby suggesting that the lower the amount of water/rainfall available to a
plant, the higher the dieback severity and vice versa. The relationship between
rainfall arid severity yielded a negative correlation coefficient (r = -f). 70).
Multiple pathogens imply that there should be integrated measures for
effective disease control. Positive effect of fertilizers indicates that proper
nutrition is crucial to alleviating effects of dieback. This study identified
dieback pathogens, showed that proper field maintenance and nutrition are
important in disease management and indicated that major fungicides
currently in use in production are ineffective. Recommendations were that·
although attention is largely on dieback, management of other passion diseases
should not be neglected. There is need to strengthen role of nursery operators
and training farmers/nursery operators on importance of tool disinfection.
Dieback management packages should target multiple pathogens. To boost
production there is need for nationwide rotational programs. This information
is crucial in dieback disease management programs and will contribute
towards reviving the passion fruit industry in Kenya.
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Description
Department of Agricultural Sciences and Technology, 97p. The SB 379 .P3W3 2013