STUDIES ON SOME ASPECTS OF ANTHRACNOSE-BLIGHT-DIEBACK COMPLEX OF CULTIVARS OF GRAPEVINES (VITIS SPP.) IN ZARIA, NIGERIA
STUDIES ON SOME ASPECTS OF ANTHRACNOSE-BLIGHT-DIEBACK COMPLEX OF CULTIVARS OF GRAPEVINES (VITIS SPP.) IN ZARIA, NIGERIA
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Date
2012-03
Authors
UYOVBISERE, EDNA NWAMAKA
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Abstract
Grapevine cultivation in Zaria, the hub of the production and spread in Nigeria, is
threatened by diseases. Diagnostic surveys conducted in June and August, 1998, and
January, 1999, to determine the important diseases for studies at the Ahmadu Bello
University, Zaria, led to the seasonality studies of the diseases from 1998-2000, which
was updated in 2011. The grapevines were found to be plagued by two distinct
devastating seasonal health problems with periodicities and associated fungi that were
consistent and therefore endemic. Downy mildew, which growers attested they
effectively managed prevailed in the dry season; while in the rainy season it was the
identified important problem needing research. The disease in the rainy season was
associated with many fungi, some of which, were proved pathogenic. For being most
preponderant with individual and collective potential to incite the syndrome observed on
grapevines in the rainy seasons, Phoma aff. multirostrata, Phomopsis sp., Phoma
sorghina and Colletotrichum gloeosporioides were implicated as the main pathogens.
The lexicon anthracnose-dieback-blight complex was adopted to reflect the syndrome
they incited. In evaluating the interactions among the main pathogens, antagonism was
shown only by the influence of Phoma aff. multirostrata which significantly (P < 0.05)
reduced the mean severity of the disease incited by the complex of Colletotrichum
gloeosporioides and Phoma sp.; while neutrality was common and synergism was most
common. In the search for alternative hosts of the main pathogens of the disease complex
among horticultural crops, guava and orange isolates of Colletotrichum gloeosporioides
significantly (P < 0.05) expanded inoculation spots on grapevines and the berries and
incited diseases with mean severity scores that were significantly (P < 0.05) higher than
those from the mango, banana and avocado isolates, whose effects were not significantly
different from the control. Isolates of Phoma sp. from different parts of the grapevine, mango and sugar apple were not significantly different from one another (P < 0.05) in
infectivity and virulence; but were more virulent than all Colletotrichum gloeosporioides
isolates. Screening of twenty four grapevine materials for their reaction to field infection
of anthracnose-dieback-blight complex, indexed by susceptibility and measured as the
mean apparent infection rate, “r”, was zero for ‘Bangalore blue’ and ‘Catawba’. Next
were ‘‘Concord’ and ‘Regina’ with “r” values that were not significantly different from
one another but were significantly (P < 0.05) lower than the successive ranks. All eight
fungicides screened against anthracnose-dieback-blight complex proved efficacious but
varied in their efficacy. Metalaxyl + mancozeb (Ridomil MZ 72, Ciba – Geigy) and
carbendazim (Bavistin, 50% FL, BASF Aktiengesellschaft) treatments, that were not
significantly different from one another, consistently resulted in diseases with the least
area under disease progress curves (AUPDC). Bi-weekly spray schedules of metalaxyl +
mancozeb (Ridomil M72) and carbendazim (Bavistin) at the manufacturers’ rates with
additional spray after each rainy day effectively controlled the disease complex. 12%
carbendazim + 63% mancozeb (Camazeb, Jubaili Agrotech Ltd) was as effective as
Metalaxyl + mancozeb (Ridomil MZ 72, Ciba – Geigy).
Description
A DISSERTATION SUBMITTED TO THE
POSTGRADUATE SCHOOL,
AHMADU BELLO UNIVERSITY, ZARIA,
NIGERIA
IN PARTIAL FULFILMENT FOR THE AWARD
OF DOCTOR OF PHILOSOPHY IN
CROP PROTECTION
DEPARTMENT OF CROP PROTECTION
AHMADU BELLO UNIVERSITY, ZARIA,
NIGERIA
MARCH, 2012
Keywords
STUDIES,, ASPECTS OF ANTHRACNOSE,, BLIGHT-DIEBACK,, COMPLEX OF CULTIVARS,, GRAPEVINES,, ZARIA, NIGERIA.