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is recommended in areas in which If cover crops are part of your crop
sclerotinia is common. rotation, do not include broadleaf crops
• Option 2 is to plant upright-growing in the mix as it can serve as a host and
cultivars later in the season to keep help sclerotinia to take hold. Radishes,
rows from closing. This practice turnips and cabbage-type crops are
can restrict yields and lead to low particularly sensitive to sclerotinia
pod height that, in turn, can greatly and in such instances it is best to
complicate the harvesting process. use only grasses as a cover crop.

Chemical control Biological control
Here the goal is to prevent the spores Biological control of the disease is still
from germinating on the flowers. For in its infancy, but the future looks very
control to be successful, the flowers promising. The primary action is to attack
must be sprayed. This process is made the sclerotia on or in the surface layer
more difficult in a soya bean field of of the soil and prevent apothecia from
which the canopy has already closed. forming. A few products are available on
Timing is therefore critical; spraying the market for this and preliminary trials Small, light-coloured apothecia.
must be done when the climate is show that this is one of the solutions that
optimal for spore release and while will have a greater foothold in future. The guaranteed. The flowering date of the
the soya bean plants are flowering. main challenge is to increase the stability entire farm can be extended over a longer
Large volumes of water must be used of the products, especially during seasons period if quick-growing cultivars are
to wash the chemical into each leaf with challenging climatic conditions. planted first and longer growers later.
axil carrying flowers. The money put Certain fields can therefore escape the
towards a preventative spray programme Tillage disease if ideal climatic conditions that
will be wasted if the timing is off. Thinking that a deep cultivation will can promote an outbreak do occur.
It is very difficult to predict climate bury the sclerotia deep in the soil, is
conditions accurately and forecast models probably the first solution that comes to Cultivar choice
are not really helpful. The main disadvantage mind. Unfortunately sclerotia can survive There is a very small difference
of chemical control is that only the sprayed underground for long periods and any between different cultivars’ sensitivity
flowers are protected; those opening a subsequent cultivation will only bring to sclerotinia. Under ideal climate
week later are not protected and can be the sclerotia back to the surface – the conditions and when a specific
infected, thus negating the entire process. problem will simply repeat itself. cultivar is in bloom, airborne spores
No-till, on the other hand, has been can infect and damage all cultivars.
Crop rotation shown to be more successful and actually However, cultivars have different
Using soya bean in rotation with another reduces sclerotinia outbreaks. Using a no-till growth habits. The more upright-
non-host crop reduces the incidence of system, sclerotia are left on the soil surface growing and less-branched cultivars
sclerotinia. Non-host crops include grasses where, when a good crop rotation system are usually less affected by sclerotinia,
such as maize, sorghum and forage grasses. is used, most will germinate the following as the field has greater air flow and
In areas where sclerotinia is commonly season and release many spores. If no is usually drier. Unfortunately, these
found, it is recommended to plant soya host is present, it will have no effect and cultivars have a lower yield potential
bean only every third or fourth season; this disease pressure will therefore be reduced. than lush cultivars with more branches.
allows sclerotia to germinate in the soil and
produce spores while no host is present. Weed management Clean seed
There are several broadleaf weeds that Seeds that have not been adequately
act as hosts for sclerotinia. Fields should cleaned can serve as a source of sclerotia
therefore be kept as clean as possible, when planted in the field. Only use seeds
especially during crop rotation. It is also purchased from a reliable source.
vital to keep headlands, contours and An integrated management practice
fences free of broadleaf weeds. These that includes all the above management
weeds can act as hosts for sclerotinia, actions will greatly reduce the negative
thereby maintaining the disease and impact of sclerotinia. Regrettably, the
increasing the source of spores in the field. disease will never be entirely preventable.

Plant date For enquiries, contact
This is one of the easiest ways to limit Nico Barnard on 082 850 1503
Sclerotia in soya bean seed. sclerotinia damage, but success is not or nico.barnard@pannar.co.za.

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