Mei 2014
70
about stripe rust?
S
outhAfrica firstexperiencedanoutbreakofwheat stripe rust
in1996, causedby thebiotrophic fungus
Pucciniastriiformis
f.sp.
tritici
. A single racewas initially identifiedandcurrently
there are three races that havebeen found inSouthAfrica.
The most dominating pathotype in the different wheat producing
areas is
6E22A
+
. This race was first identified in 2005 and unlike
preceding stripe rust races in South Africa, it is virulent on the
resistancegene
YrA
.
Stripe rust ismore prevalent whenweather conditions are cool and
wet as this is ideal for the proliferation of the fungus. Therefore,
susceptible cultivars grown in cooler areas such as the eastern
FreeState are vulnerable to stripe rust infection.
Stripe rust is a variable pathogen consisting of pathotypes with
different virulence spectra. Optimum weather conditions for the
proliferation of stripe rust are temperatures between 10°C and
15°C and the presence of free water. During periods of hot and dry
weather, infection ceases, but it often restartsduring cool andmoist
conditions.
What can you do you when you suspect
infections?
Firstly, a correct identification of the disease needs to be made. A
typical signof stripe rust is thepresenceof small, yellowishpustules
on leaves and sheaths arranged in conspicuous stripes (
Photo 1
).
In cases of severe infection on susceptible plants, pustules also
formonwheat heads, and areeasily identifiedby their yellow colour
(
Photo 2
).
If stripe rust is correctly identified in the field, theuseof chemicals is
sometimes essential. However, certain factors should be taken into
consideration suchas, thegrowth stageof the crop, susceptibilityof
thecultivar/sused, yieldpotential and thecosts involved in fungicide
applications.
The timing of fungicide application is critical since plants are most
vulnerable during the early growth stages and this is when most
of the damage occurs. Spraying after the soft dough stage is often
unnecessary as the chances of thedisease affecting yield is low.
If the cultivar is susceptible, with a high yield potential, the timing
of the fungicide application should ensure that the crop is protected
especiallyduring the kernel fillingperiod.
Even during the absence of stripe rust, the crop needs to be
thoroughly monitored up to the fully emerged flag leaf stage for
signs of thedisease.
Table 1
indicates fungicides that are registered for control of stripe
rust in South Africa as well as the active ingredients of these
fungicides.
ON FARM LEVEL
Wheat stripe rust / Pathotype /Weather conditions /Cultivars
Pest control
KRISHNANAICKER,
ARC-Small Grain Institute, Bethlehem
PRODUCTNAME
ACTIVE
Amistar Xtra
Azoxystrobin/cyproconazole
Improve 250SC
Indicate 250SC
Azoxystrobin/epoxiconazole
Granit EC
Bromuconazole
Duett
EnduraPlus
SopranoC
Carbendazim/epoxiconazole
Flusilazim 375SC
LyricC
PunchC
SpartaSC
Carbendazim/flusilazole
Early Impact
Carbendazim/flutriafol
Propazim 250SC
PropiconazolePlus 250SC
Carbendazim/propiconazole
Folicur C 300SC
Carbendazim/tebuconazole
Artea
Cyproconazole/propiconazole
Endura 125SC
Opus
Epoxiconazole
Capitan 250EW
Flusilazole
Impact
Flutriafol
Richter
Hexaconazole
Ag-Propiconazole
Bumper 250EC
Propicon 250EC
Propicon 500EC
Propiconazole 250EC
PropimaxEC
Propizole 250EC
Sanazole 250EC
Tilt
Propiconazole
Prosper Trio
Spiroxamine/tebuconazole/
triadimenol
Tebuconazole 250EC
Tebuconazole 250EW
TebuDew
Orius 200EW
Orius 250EW
Corona 250EW
Folicur 250EW
TebCure 250EW
Tebuzole 250EW
Volteb 250EW
Tebuconazole
Badger 15 FS
Triadimenol
Flite
Triticonazole
TABLE 1: REGISTERED FUNGICIDES FOR THE CONTROL OF STRIPE
RUST INSOUTHAFRICA (AVCASA, 2013).
