Winter wheat is a potentially high-yielding but high-cost crop. Wheat production is a serious business where many things can go wrong and not all of them can be controlled.

The prolonged wet summers of 2007, 2009 and 2012 showed the consequences of high ear disease levels. This article focuses on the best options for effective ear disease control on wheat.

Ear blight control

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This is a very complex disease with a number of Fusarium and Microdochium species capable of contributing to its incidence and severity. Ear blight and mycotoxin contamination have received much scientific attention in recent years with questionable benefit for on-farm control procedures. I believe there is a very simple management approach needed to counter this disease threat. I must also note the poor commercial advice sometimes given to use sub-optimal (reduced) fungicide rates that will be relatively ineffective.

If we get wet weather at flowering, with prolonged periods of crop wetting and high humidity, then there is a medium to high risk of ear blight infection.

Our varieties contain moderate genetic resistance to the ear blight complex and this is very important in the control of this disease complex. In recent years most of our commercial varieties had a resistance rating of six to seven.

If a variety has a resistance rating of five, or lower, it is a dodgy option for Irish conditions. Even the resistance range of six to seven leaves commercial varieties vulnerable to significant infection in high disease pressure years.

If we get a dry, sunny flowering period (2013), or mixed weather (2011), then the risk of infection is lower and there will be more flexibility around fungicide use.

In a commercial scenario, T3 fungicides can have excellent cost-benefit potential based on foliar disease control. In high yield crops robust fungicide treatments are advised and essential.

While disease incidence may be uncertain, the risk is somewhat predictable. The table below outlines a range of factors known to impact on risk.



I believe this disease complex is also hugely influenced by location. Even in the wet June of 2012 there were massive differences in the levels of ear blight infection observed in different areas.

Our trials data for this severe infection season showed individual varieties carrying very high infection levels at southerly locations and low to moderate infections at eastern locations. Where infection levels are above 10% to 15%, the yield and quality effects are severe.

Product options

Product choice is simple – prothioconazole is the best active on ear blight infection and it can show good to very good efficacy on a moderate to severe infection when applied properly.

A robust rate of prothioconazole is very important and 200g a.i./ha (0.8 l/ha Proline) will perform clearly better than 150g/ha (0.6 l/ha). The trials showed that 125g/ha of prothioconazole (0.5 l/ha Proline) is a weakish dose with/without a partner triazole.

A loaded triazole treatment combining metconazole (next strongest) or tebuconazole or epoxiconazole (weaker) will add significantly to efficacy. If your product choice is Prosaro, then the rate should be 1.1 to 1.2 l/ha to seriously target effective ear blight control.

In a trial on Santiago in Meath in 2012, which had a moderate ear blight epidemic (25% infection on the untreated control), the loaded triazole treatment gave 50% to 60% control at lower doses and up to 75% control when high doses were applied.

The high doses were the most cost-effective at this site in that season. The very high doses with high triazole loading were clearly better on both ear blight control efficacy and grain yield.

Timing

Perhaps the biggest surprise from these results was that they were achieved from a timing estimated to be at least seven to 10 days later (after GS 69) than the optimum of early to mid-flowering.

Many previous studies in recent decades used inoculated trials with artificially-enhanced conditions for infection. But I have always suspected that, in a high disease pressure scenario in Ireland, the disease infection event may be uniquely different to an artificial situation.