FOCUS
Integratedpest control
Special
September 2014
54
Moreon the chemical control
ofwheat rusts
F
ungal diseases such as leaf and stem
rusts, leaf andglumeblotchesaswell
as powdery mildew are commonly
found on bread wheat in the major
wheat growing regions, suchas theWestern
Cape.
Under favourableweather conditions, these
diseases can significantly reduce the yield
andqualityof susceptiblewheat. Therefore,
disease control practices are mostly
required inorder toprevent yield losses.
Fungicides are one of the most important
components of adisease control strategy in
wheat. Particularly when resistant cultivars
are not available or when the resistance in
existing cultivars becomes ineffective due
to the emergence of new races, fungicide
intervention provides an effective and
practical means of reducing disease
outbreaks.
The ARC-Small Grain Institute understands
the value of fungicides in the management
of wheat diseases and has, over the past
20years, continuallybeen testing fungicides
that are entering the market in order to
identify superior products.
The results have assisted producers in the
profitable control of wheat diseases using
fungicides. As a continuation of this long-
term project, field trials were conducted
at Malmesbury and Tygerhoek in the
Western Cape during the 2013/2014 season
to determine the response of two wheat
cultivars to fungicide applications at seven
leaf and flag leaf growth stages (
Table 1
).
The two cultivars evaluated were SST 88
(susceptible to leaf and stem rust and
moderately resistant to stripe rust) and
SST 056 (moderately resistant to leaf
and stripe rust andmoderately susceptible
to stem rust). The results of this study are
summarised in the article.
Leaf and stem rust were frequently
observed in the experimental plots mainly
on the susceptible cultivar SST 88 both at
Tygerhoek and Malmesbury. Untreated
plots of SST 88 at Tygerhoek displayed
over 75% and 30% final leaf and stem rust
severity, respectively.
At Malmesbury, the average leaf and
stem rust severity on fungicide untreated
SST 88 was over 65% and 10%, respect-
ively, suggesting that disease pressure
was slightly lower at Malmesbury than at
Tygerhoek.
Cabrio applied at seven leaf stage followed
by Folicur application at flag leaf stage and
Abacus and Folicur applied at seven leaf
and flag leaf stages, consistently resulted
in a relatively lower level of leaf and stem
rust on SST 88. Disease severity on
SST 056 was very low (≤ 5%) at both
localities, indicating that thiscultivarhasstill
retained its resistance to leaf and stem rust.
Fungicide application significantly increas-
ed theyieldofSST88andSST056at the two
localities. At Malmesbury, SST 88 sprayed
with Cabrio at seven leaf stage followed
by Folicur at flag leaf stage, Cabrio and
Abacus applied at both stages, andProsper
Trio and Prosaro applied at seven leaf and
flag leaf stages, respectively, resulted in a
significantly higher yield than the untreated
control (
Graph 1
).
Cabrio and Folicur applied to SST 88 at
seven leaf and flag leaf stages, respectively,
resulted in the highest yield increase of
0,943 ton/ha over the untreated control.
TAREKEGN TEREFE
and
PETRUSDELPORT,
ARC-Small Grain Institute
SAGrain/
Sasol Nitrophoto competition
