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October 2016
ON FARM LEVEL
Integrated pest control
Graph 1: Percentage of producers indicating the use of various sunflower
production practices and voicing of farming concerns (2012/2013).
Graph 3: Percentage of producers indicating the use of various sunflower
production practices and voicing of farming concerns (2014/2015).
Graph 2: Percentage of producers indicating the use of various sunflower
production practices and voicing of farming concerns (2013/2014).
In contrast, both localities (Table 1) and cultivars (
Table 4
) showed
significant differences during the 2013/2014 season.
Cultivar SYN 4200 was less susceptible to Alternaria leaf spot
when compared to SYN 4045, PHB 65A25 and PAN 7049 in the
2013/2014 season (Table 4). In both the 2013/2014 and 2014/2015
seasons the severity of Alternaria leaf spot was significantly greater
in Potchefstroom compared to other localities.
Other prominent diseases such as brown rust (84%) in Arlington,
Sclerotinia head rot (31%) in Delmas and Phoma stalk rot (96%) in
Naboomspruit were observed in producers’ fields during the
2012/2013 season (Table 1).
In the 2013/2014 season, the spread of Sclerotinia head rot in-
creased considerably, occurring in all production areas and causing
severe damage to sunflower fields (Table 2). Heavy rainfall received
earlier in the season contributed to the development of Sclerotinia
head rot epidemics. Compared to other localities the most severely
affected locality was Lichtenburg (Table 2).
Cultivar SYN 4200 was less susceptible to Sclerotinia head rot
when compared to PAN 7049 in the 2013/2014 season (Table 4).
Bacterial head rot was recorded in one producer’s field in Dwaal-
boom and brown rust was recorded in Arlington, Bloemfontein and
Welgelegen.
No Sclerotinia incidences were recorded in the 2014/2015
season. The questionnaire results for the 2012/2013, 2013/2014 and
2014/2015 seasons’ surveys showed that diseases and drought
were the major sunflower production constraints identified by
producers. Most producers prefer crop rotation, planting their sun-
flowers in an east-west and south east-north west row direction,
using row widths wider than 80 cm and plant densities of above
30 000 (Graph 1,
Graph 2
and
Graph 3
).
Conclusions
There were great variations in disease incidence and severity over
localities surveyed, which is influenced by primary inoculum levels,
hybrid susceptibility and seasonal climatic conditions. For exam-
ple, in the 2012/2013 and 2014/2015 seasons there was a drought
throughout the major sunflower production areas and Sclerotinia
head rot was not prevalent.
High rainfall received during the 2013/2014 season prompted
Sclerotinia head rot epidemics in all sunflower production areas.
Therefore continuation of annual sunflower disease surveys will
help identify and prioritise diseases of major concern to sunflower
producers and subsequently serve as a landmark to raise awareness
of disease trends.
After surveys over three seasons the major widespread sunflower
disease problems appear to be Alternaria leaf spot and Sclerotinia
head rot.
For more information, contact Moses Ramusi at
ramusim@arc.agric.zaor 018 299 6225.
National sunϐlower disease surveys