Planning ahead will be critical for canola and pulse growers looking to reduce the risk of sclerotinia stem rot in 2017.
Growers in areas across the southern region who saw outbreaks of sclerotinia in 2016 should be careful to not plant susceptible crops in the same paddock where the disease was seen last year.
The current recorded host range for sclerotinia is more than 400 plant species.
This includes common host crops which make up part of dryland cropping rotations in the southern region such as canola, chickpeas, lentils, lupins and field peas.
Broadleaf weeds such as wild radish, shepherd’s purse and capeweed are also known hosts of sclerotinia.
Crop consideration is one of several pre-season measures NSW DPI plant pathologist Kurt Lindbeck is recommending growers take prior to planting the 2017 crop.
Previous research has shown that sclerotinia can cause yield losses of up to 30 per cent in canola.
‘‘It is not yet clear just how much yield loss sclerotinia causes to pulse crops, as previously the disease has not been regarded as a consistent enough problem to warrant in-depth research,’’ Dr Lindbeck said.
‘‘Canola is a very good host for sclerotinia and now we are starting to see more carryover of the disease into pulse crops as they become a bigger part of the cropping rotation.’’
The main survival mechanism of sclerotinia is sclerotia, which are hard, black bodies that develop inside infected canola and pulse stems.
For this reason, they can be quite easily carried in loads of seed and were found in canola and pulse grain deliveries across Australia during the 2016-17 harvest.
If growers are retaining canola and pulse seed for planting, Dr Lindbeck advises them to consider grading the seed to remove sclerotia.
Sclerotia can survive in soil for at least five years, however, they have been known to survive in soil when buried at a depth greater than 3cm for up to 10 years.
‘‘For canola, which we know can flower for up to eight weeks in certain regions, it is the earlier infection events that are the most damaging, while the later infections on lateral branches don’t cause the same level of yield loss,’’ Dr Lindbeck said.
He said weather conditions during flowering influenced the development of sclerotinia.
‘‘Dry conditions during flowering and petal fall can prevent the development of the disease, whereas moisture during flowering and petal fall will enable the disease to develop.
‘‘The frequency of sclerotinia outbreaks in previous seasons can also help growers to determine their risk of sclerotinia.’’