Barley and wheat T2 fungicide management

T2 fungicides are a critical component of disease management in wheat and barley crops. Applied at the flag leaf stage, these sprays help protect the upper leaves which are vital for grain filling and yield.

In wheat the flag leaf contributes significantly to the final yield and can intercept up to 40 % of the available light. Keeping it free of diseases like septoria and rusts is vital. The barley flag leaf is much smaller so contributes less to the final yield but it is still important to keep it green and free of disease for as long as possible. 

Timing of application

The optimal timing for the T2 application in wheat is GS 39 or when the flag leaf emerges. Barley application falls later, between GS 39 to 45, otherwise known as the toothbrush stage when the awns are visible. Applying the right fungicide at this stage ensures protection of the flag leaf and upper canopy during the critical period of grain development.

Latent period

Many factors affect the length of the latent period or the time between infection and appearance of symptoms:

º High temperatures (shorten it)
º Pathogen species (Septoria can range between 14 to 28 days)
º Variety susceptibility
º Pathogen spore count at time of infection
º Humidity and rainfall
º Nutrient availability

The spray interval between T1 application and T2 should not exceed 21 to 25 days.

Even with the modern SDHI fungicides, you will only have curative activity for three to five days after the fungus has penetrated the leaf.

Resistance management

Fungicide resistance is common and can be detected through the following processes:

º A change in inhibitor site
º Reduced uptake or accumulation of active ingredients
º Detoxification of the fungicide
º Development of override pathways
º Increase in virulence.

To delay development of resistance, it is important to rotate fungicides with different modes of action, including a multi-site fungicide at T2 with your triazoles, strobilurins, picolinamide (Group 21). SDHIs (succinate dehydrogenase inhibitors) can be beneficial in the fight against resistance. Seek advice from your PGG Wrightson Technical Field Representative on dose rates, because applying too little fungicide increases the chance of fungicide resistance occurring on your farm. 

Integrated disease management

T2 fungicide sprays should be part of any integrated disease management strategy. This includes crop rotation, using resistant varieties, optimising plant density, cultivation, destruction of green bridges, and ensuring adequate nutrition for the plants. Ensure crops are regularly monitored for disease pressure and do not delay in applying the correct fungicide, at the label rate, for the right situation.

For help managing barley and wheat T2 fungicide, contact your local PGG Wrightson Technical Field Representative today.