EPIDEMIOLOGY OF COWPEA BROWN BLOTCH INDUCED BY COLLETOTRICHUM CAPSICI AND ASSESSMENT OF CROP LOSSES DUE TO THE DISEASE
EPIDEMIOLOGY OF COWPEA BROWN BLOTCH INDUCED BY COLLETOTRICHUM CAPSICI AND ASSESSMENT OF CROP LOSSES DUE TO THE DISEASE
No Thumbnail Available
Date
1994-10
Authors
ALABI, OLUFUNMILOLA
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Colletotrichum capsici (Syd.) Butler and Bisby which
induces brown blotch in cowpea was found to grow and sporulate
between 20 and 3 5°C on potato dextrose agar incorporated with
streptomycin, the optimum temperature being 25°C. When plants
aged 1-6 weeks were inoculated with the conidial suspension of
the fungus containing 4.16 x 1Q5 to 3.7 5 x 106 conidia/ml,
plants aged 1 or 2 weeks at inoculation were more severely
affected than older plants aged 3 to 6 weeks at the time of
inoculation. There was a highly significant (P=0.01)
interaction between plant age at inoculation and inoculum
concentration. The incubation period was 2-3 days for all the
aerial parts of the plants inoculated irrespective of age.
C. capsici sporulated faster on relatively tender petiole
tissues than on less succulent stem tissues. The latent
period varied from 5 to 16 days, depending on the plant part.
Cowpea sown early at the third week of July or first week
of August (when there was high and frequent rainfall) had
higher incidence of brown blotch than those sown late August.
In addition the quality of the grain produced in the early
sown crop was poor (being mostly wrinkled) while that of the
late sown crop, was relatively high, being mostly wholesome
and non-discoloured.
It appears that both rainfall and relative humidity
enhance the development of brown blotch in cowpea provided
that there is enough rainfall and consequently, sufficiently
high relative humidity for disease establishment, although
among the two factors, the progress of the disease appears to
depend more on relative humidity.
Loss in grain yield of cowpea due to brown blotch ranged
from 10% for variety IT83S-742-11 to 44% for Ife Brown
Description
A thesis submitted to the Postgraduate School,
Ahmadu Bello University in partial fulfillment of the
requirements for the degree of Doctor of Philosophy
DEPARTMENT OF CROP PROTECTION
FACULTY OF AGRICULTURE
AHMADU BELLO UNIVERSITY
ZARIA, NIGERIA
October, 1994
Keywords
EPIDEMIOLOGY,, COWPEA,, BROWN,, BLOTCH,, INDUCED,, COLLETOTRICHUM CAPSICI,, ASSESSMENT,, CROP,, LOSSES,, DISEASE.