STUDIES ON THE FALSE SMUT OF RICE, ORYZA SATIVA L., INDUCED BY USTILAGINOIDEA VIRENS (CKE.) TAK
STUDIES ON THE FALSE SMUT OF RICE, ORYZA SATIVA L., INDUCED BY USTILAGINOIDEA VIRENS (CKE.) TAK
No Thumbnail Available
Date
1995-05
Authors
MONDAY, OBAIGBORUEN AHONSI
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The incidence and severity of false smut of rice incited by
(Ustilaainoidea virens (ke.) Tak.) in the major rice producing
areas of Edo State was investigated in 1992. Although the
disease was present in all the areas surveyed, it was most
prevalent and severe in Ovbiowun-Emai, and Uokha, both in Owan
East of Edo State. The mean incidence and severity of false smut
in the area between mid-August and mid-September were 28.5% and
13.9% respectively compared to 8.9% and 3.4% for late-September
to mid-October.
A pathogenicity trial conducted at the University of Benin,
Benin City in 1993 revealed that false smut was reproduced only
when rice panicles were sprayed with either chlamydospores or
conidia suspension at 'heading' stage. Inoculation at 'booting'
or 'milk-grain' stage respectively did not cause any infection.
Field trials were conducted at Ovbiomun-Emai, in 1993 and
1994 to determine the effect of sowing date, plant density,
varietal resistance, and fungicidal sprays on the incidence and
severity of the disease.
Rice sown with the early rains, between early-April and
early-May, were virtually free from false smut infection. On the
other hand, mid-season sowing, between mid-May and early-June,
recorded the highest incidence and severity of false smut.
There were no significant differences (P = 0.05) among the
severities of false smut at three spacing levels (0.2 x 0.2m, 0.4
x 0.4m and 0.4 x 0.8m) tried.
Of the seven rice varieties screened against false smut under
field conditions, at two sites, ITA 316, Ex-china and IRAT 170
were the most resistant. The other four varieties were
susceptible.
Delsene M, Benlate, Tecto, and Cupravit, at the three
concentrations tried in-vitro, completely inhibited mycelial
growth of U. virens; while Dithane M-45 and Rovral reduced
mycelial growth by 62.2% and 47.8% respectively. Four sprays
each of the six fungicides at an interval of 7-days, starting at
the sighting of the first 'boot', were found to reduce incidence
and severity of the disease in the field. However, the best
result was obtained by spraying with cupravit. This resulted in
75.9% reduction in disease incidence and significantly increased
grain yield by 43.2% when compared with the control. Dithane M-
45 sprays also resulted in 47.0% disease reduction, but did not
increase grain yield significantly. Delsene M sprays apparently
gave a 100% disease control, but was highly phytotoxic to the
rice plants at the recommended rate.
Description
A THESIS SUBMITTED TO THE POSTGRADUATE SCHOOL,
AHMADU BELLO UNIVERSITY, ZARIA
IN PARTIAL FULFILLMENT 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
MAY, 1995
Keywords
FALSE SMUT,, RICE,, ORYZA SATIVA,, USTILAGINOIDEA,, VIRENS