IDENTIFICATION, PATHOGENICITY AND MANAGEMENT OF FUNGI ISOLATED FROM CASTOR (Ricinus communis L.) IN SAMARU, NIGERIA
IDENTIFICATION, PATHOGENICITY AND MANAGEMENT OF FUNGI ISOLATED FROM CASTOR (Ricinus communis L.) IN SAMARU, NIGERIA
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Date
2008-09
Authors
MAMZA, WADIAM SEBASTIN
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Abstract
The fungi isolated from infected castor leaves were Fusarium sp, Helminthosporium sp
and Curvularia sp. Pathogenicity tests was conducted on the fungi and Fusarium sp was
pathogenic on castor and its pathogenicity was confirmed using Koch’s postulate. The
Fusarium sp was later identified to be Fusarium pallidoroseum by International
Mycological Institute (IMI) Egham, London. Plants at different ages (11, 18 and 25 days
old) were inoculated using three methods (spray, smear and soil inoculation). Twenty one
day old castor plants were inoculated with inoculum at different densities (103, 105, 107,
1010 conidia / ml and water) and assessed in order to determine at what density the
pathogen can induce infection. Six fungicides were evaluated in vitro at three
concentrations (one and half the recommended, recommended and half recommended
rates) for their effect on growth and regrowth of mycelia, sporulation and conidia size of
Fusarium pallidoroseum. Five of the fungicides tested in the laboratory were further
evaluated at two concentrations (recommended and half recommended rates) for their
efficacy in the management of leaf blight induced by Fusarium pallidoroseum in vivo.
Effect of three sowing dates on disease incidence and severity was assessed on two castor
types during the 2006 wet season. During the pathogenicity tests it was observed that,
younger plants were more susceptible to infection than older plants. For the in vitro
evaluation of fungicides, it was observed that all the fungicides (benomyl, benomyl +
thiram, mancozeb, metalaxyl-M + thiomethoxam + difenoconazole, tricyclazole and
carbendazim + mancozeb) at all the concentrations tested inhibited mycelial growth,
sporulation, and reduced conidia size and mycelial regrowth of the fungus. Benomyl,
benomyl + thiram and tricyclazole completely inhibited mycelial growth and sporulation
of the fungus at the three tested rates. Metalaxyl-M + thiomethoxam + difenoconazole,
carbendazim + mancozeb inhibited mycelial growth and sporulation only at one and half
rate but not at recommended and half recommended rates. Inhibitory effect of all the
fungicides on mycelial growth and sporulation were greatest at one and half
recommended rate. Benomyl, benomyl + thiram, mancozeb, carbendazim + mancozeb
and tricyclazole reduced the rate of disease development on 21 - day- old inoculated
castor plants in the screenhouse at recommended than at half the recommended rate.
Large seeded castor sown on July 27 had less disease severity and higher yield compared
with plants sown in August 3 and August 11. For the small seeded type, August 3 sown
plants had high disease severity and more yield than those sown on other dates. F.
pallidoroseum is the cause of leaf blight, seedling rot and wilt of castor in Samaru. The
younger plants (11 days old) were more susceptible to infection. The evaluated
fungicides can be used to control F. pallidoroseum on castor. Sowing late, resulted in
poor seed germination thereby affecting bean yield negatively.
Description
A THESIS SUBMITTED TO THE POSTGRADUATE SCHOOL
AHMADU BELLO UNIVERSITY, ZARIA,
NIGERIA
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE IN CROP PROTECTION
DEPARTMENT OF CROP PROTECTION
FACULTY OF AGRICULTURE
AHMADU BELLO UNIVERSITY,
ZARIA, NIGERIA
SEPTEMBER, 2008
Keywords
IDENTIFICATION,, PATHOGENICITY,, MANAGEMENT,, FUNGI ISOLATED,, (Ricinus communis L.),, SAMARU,NIGERIA