Teagasc tillage advisors are highlighting the importance of targeting septoria control on leaf ‘three’ of growing wheat crops.
According to Dr. Steven Kildea, septoria is the most economically important disease of winter wheat.
“It is a wet weather disease. It is important to protect leaf ‘three’ from disease. But this approach will also give protection to leaves ‘one’ and ‘two’,” he explained.
“These are the key leaves that will capture sunlight, converting it into carbohydrate.”
So important is the identification of leaf ‘three’ that Kildea recommends that farmers should physically take plant samples from a field, and dissect them out on a table indoors.
“Wheat plants go through vegetative and reproductive phases. The first sees the creation of new tillers, the second sees the emergence of the ear.
“The third leaf can be difficult to identify within a field scenario. This is why it is important to bring plants indoor and physically count back along the stems in order to identify leaf ‘three’.
“So by targeting leaf ‘three’ with a fungicide the grower is effectively insulating the tope part of the wheat canopy from disease pressure that might be at a lower level.”
Winter wheat
Targeting leaf ‘three’ also protects the flag leaf of the growing wheat plant.
With the loss of chlorothalonil, Teagasc is now recommending the use of multi-site folpet to reduce disease resistance and septoria control.
Two applications are recommended, each at a rate of 1.5L/ha. The first should be applied at the leaf three stage, the second when the flag leaf is fully emerged. The effective use of a fungicide at flag leaf can deliver yield increases of up to 1.7t/ha.
Teagasc advisors are also pointing out that there is little opportunity to reduce fungicide application rates in years when a high disease pressure exists.
“The application of a fungicide when the third leaf is fully emerged also gives a level of protection to second leaf, which will be in the process of unfurling at that stage in the development of the plant,” Kildea continued.
“The follow-up spray should be applied to protect the flag leaf. This approach maximises the efficiency of the fungicides used, while also minimising the cost incurred by the grower.
“Fungicides should not be applied to crops at times when plants are under stress. This can occur in the wake of flooding, drought or the recent application of other chemistries,” he concluded.