Disease Watch 2016 2nd Edition

Arable Fungicides Disease Watch Bayer

Welcome to Disease watch, a season long programme designed to keep you informed and ready to tackle diseases invading arable farms around the country.

18 October 2016 - A critical time for disease control

Welcome to this edition of Disease watch, a season long programme designed to keep you informed and ready to tackle diseases invading arable farms around the country.

Wheat - Southland

With crops at GS32 final leaf three has emerged. Protecting leaf three is important for two reasons: it is one of the yield producing leaves and secondly, if disease is allowed to develop on leaf three, when the flag leaf emerges it does so at the same height in the canopy as the infected leaves and direct transfer of Septoria leaf blotch takes place.

With the prevailing wet weather, warm conditions and active Septoria on the lower leaves it is shaping up to be a challenging year for any crop not adequately protected from disease.


Wheat - South Canterbury

Like other regions of New Zealand, crops in South Canterbury are showing a high incidence of Septoria leaf blotch.

While it is mainly the lower leaves infected at the moment, sporulating lesions are very easy to find (see left hand image) and the disease is now moving up on to leaf three (see image below).

In addition, low levels of leaf rust and tan spot are being reported. It pays to look carefully for these as these diseases can develop rapidly under the right climatic conditions.

South CanterburyWheat

Wheat - Mid Canterbury

David Parker, Regional Sales Manager for Mid-Canterbury, examining a Prosaro treated crop as part of Disease watch.

Unlike the untreated crops we have been examining for these updates, this crop is very clean of disease.

Check out the stem base shot of this crop.

Mid Canterbury Wheat

It isn’t just Septoria that is attacking wheat this season in Mid-Canterbury as this image shows. This is the most aggressive mildew infection Bayer has seen for a long time on a winter wheat crop.

(Below) Not strictly a disease but Barley Yellow Dwarf Virus (BYDV) is now showing. Note the bright yellow and also purple leaves. This virus can attack wheat, barley and oats.

Wheat - Manawatu

Wheat - Manawatu

Untreated wheat in Manawatu showing an aggressive Septoria leaf blotch infection. Note the emerging flag leaves in the centre of the image.

The flag leaf is critical for yield production and in this crop they are emerging at the same level as infected leaves. A “perfect storm” scenario for disease development! All it needs is moisture, some wind and disease will be transferred throughout the canopy.

(Below) Certainly not what Bayer staff expect to see in mid-October. Wheat in full flower with Septoria crawling all over the upper leaves. This clearly illustrates the disease threat that is out there this season.

Manawatu Wheat in ear

Disease control in wheat

In situations such as this, adopting a three spray programme utilising Aviator Xpro at GS32 and GS39 followed by Proline + a strobilurin fungicide at GS60-69 will provide excellent control of SLB as well as late infections of leaf rust. Click here to see the recommended Bayer spray programme for wheat

Barley - Southland

With crops reaching awns emerging and with plenty of moisture, warm conditions and scald throughout the canopy it is critical that you apply a robust fungicide now. This fungicide will also control Ramularia leaf spot – perhaps the most devastating late season disease of barley.

Barley Southland

Barley - South Canterbury

Scald is the predominant barley disease throughout South Canterbury although leaf rust is starting to be found and net blotch can be a problem, especially for second year barley crops. This shows a typical scald lesion that is still actively producing spores - the greyish green, “water soaked” appearance is typical of active lesions. Spores from lesions such as these are able to wash down the leaf to lodge in the leaf axil. Here they germinate and the subsequent lesions are able to kill the entire leaf.
South Canterbury Barley

Barley - Mid Canterbury

It is evident that scald is widespread throughout the South Island this year.

The crop held aloft (below on left) has been treated with Delaro and now approaching GS39, is just at the right stage to receive an application of Aviator Xpro as a T2 fungicide to protect against scald and Ramularia leaf spot.

Contrast this with the untreated crop (below on right) which is heavily infected with scald, even on the upper leaves. If you look carefully towards the bottom left of the image, you will see a number of leaf rust pustules.

Barley Mid Canterbury

What is the below barley disease? The Bayer team is having this scientifically identified but we expect it to be a mixture of net blotch and physiological leaf spotting.

Mid Canterbury Barley

Disease control in barley

For general disease control in barley adopting a two spray programme utilising Delaro at GS32 followed by Aviator Xpro at GS39 will provide excellent control of scald, net blotch and Ramularia leaf spot. Late infections of leaf rust will also be controlled. Click here to see the recommended Bayer spray programme for barley.