Wheat Yellow Leaf Spot trial

By Damian Jones, ICC

Key messages:ICC_Trial_Summary_Book_ cover

  • No treatment (previous stubble susceptibility, fungicide or variety resistance) had any effect on wheat yield.
  • In most years Yellow Leaf Spot accounts for minimal yield losses.

Yellow Leaf Spot, has become a widespread and important disease of wheat in Victoria. It has been supported by stubble retention, intense wheat production in the rotation and wide spread cultivation of susceptible wheat varieties.

Yellow leaf spot caused by the fungus Pyrenophora tritici-repentis, is predominantly a stubble-borne disease. This fungus survives between crops on cereal stubbles as mycelium in stubble and can survive on stubble for up to two years, if seasons are a very dry.

In the late summer/early autumn the fungus develops small black fruiting bodies on the stubble. The fruiting bodies contain large numbers of sexual spores which are forcibly ejected during cool (15°C) humid conditions. Spores land on nearby wheat plants and will infect leaves if they remain wet for more than six hours.

In isolated cases, in particular when susceptible wheat varieties are sown into wheat stubble, heavy infestations of yellow leaf spot can caused yield loss when the flag and upper leaves become infected.

In most years, yellow leaf spot only infects the lower leaves and is generally regarded as causing limited yield loss. However, research at DEDJTR Horsham in 2012 and 2013 found infection of the lower leaves by the yellow leaf spot fungus reduced the yield of resistant varieties (MR and MRMS) by approximately four per cent and susceptible varieties (S and SVS) by approximately 15 percent (from DEDJTR disease notes).

Method

In 2015 a trial was sown with two varieties, Bolac (MS-S) and Corack (MRMS) on Corack and Phantom (S-VS) stubble. The fungicide strategy was to spray when the risk of infection was increased, ie in front of rainfall events and irrigation.

Two fungicides have been used, a triazole and a strobulurin.

The triazoles are the lower cost strategy, while the strobulurin is a fungicide that has prolonged protection. Neither fungicide will protect unsprayed leaves, hence the strategy to spray each time conditions are likely to favour infection as the leaves that have emerged since the last spray are unprotected.

The trial was sprayed four times – June 12, July 9, July 31 and August 31.

Results

Very low levels of YLS were observed early in the season, but little disease was present from August on wards.

Table 1. Yield of Bolac and Corack wheat, 2015.
Harvest Data Bolac Corack
Treatment

Yield (t/ha)

Yield (t/ha)
Not Sprayed

4.70

4.95

Tilt

4.50

4.45

Amistar

4.66

4.73

P

0.754

0.235

LSD

NS

NS

CV%

10.0

10.3

No treatment (previous stubble susceptibility, fungicide or variety resistance) had any effect on yields.GRDCLogoStacked_TM_CMYK

The stubble project – maintaining profitable farming systems in Victoria and Tasmania with retained stubble (project number BWD00024) is funded by the GRDC.

A printer-friendly version of this trial report can be accessed here.

Advertisements

About BCG

Birchip Cropping Group Inc. (BCG) is a not-for-profit agricultural research and extension organisation led by farmers in the Victorian Wimmera and Mallee.
This entry was posted in Disease management, Research results and tagged , , , , , , . Bookmark the permalink.

One Response to Wheat Yellow Leaf Spot trial

  1. Pingback: 2015 field trials | The stubble project: Victoria and Tasmania

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s