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Some aspects of the control of Altenaria blight of sunflower
incited by Alternaria helianthi (Hans.) Tub. & Nis. were studied
in Samaru during the 1991 and 1992 wet seasons. Laboratory
studies confirmed that the pathogen is seed-borne and that ail the
five sunflower varieties evaluated were susceptible to the
disease. In both glasshouse and field trials, it was demonstrated
that seed treatment with metalaxyl + carboxin, carbendazim +
maneb, mancozeb and carbendazim + iprodione each at. 1,2 and 5g
a.i/kg seed significantly increased seedling emergence and also
reduced incidence of seedling blight, numbers of leaves shed and
leaf spot severity compared with the untreated check. Metalaxyl
+ carboxin at 1 and 2g a.i/kg seed gave the overall best results.
The three fungicides (benomyl, Carbendazim + maneb and
mancozeb) evaluated for the control of Alternaria leaf spots
significantly reduced the leaf spot severity compared with the
unsprayed check. Carbendazim + maneb at 2.4kg a.i/ha gave the
best leaf spot control probably because of its systemic and
protectant qualities.
Whereas the differences among the five sunflower varieties
(Record, Funtua, Chernaanka, Isanka and Smena) screened for
resistance to Alternaria blight in respect of needling emergence,
numbers of leaves shed prematurely and blight severity were not
significant during the 1991 wet season, those of 1992 were
significant. Smena bad the highest blight- severity while Funtua
and Chernaanka had the lowest.
An integration of chemical and other disease control
strategies has been recommended for control of Alternaria blight,