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March 23, 2012

Raising the nutritional as well as disease defences

While we still haven’t had much rain, we’re thankful for recent foggy days and lack of wind.  They’ve kept moisture losses to a minimum wherever we have a canopy, allowing our winter crops to grow away strongly.

With temperatures climbing and sunlight intensity building, our key priority now is to support  cereals and rape through stem extension to flowering when nutrient demands are at their peak.   Especially so as the forecast into early April gives us little comfort on the rainfall front.

Larger canopies, very rapid spring growth and limited soil moisture have combined to make magnesium deficiency more widespread than I’ve ever seen it in OSR. So we’re adding a big dose of foliar magnesium as well as a decent boron top-up to our stem extension fungicide.

As we’ve yet to see significant levels of disease in most crops, we’re basing this firmly on metconazole for its growth regulation value and for the useful start it gives to sclerotinia control.

We’re including a good quality pyrethroid and adjuvant in the stem extension spray wherever pollen beetles are anywhere near threshold levels. They’re easy to find in most crops. And as temperatures are likely to reach the critical 15oC on a regular basis in the next week populations could well take-off in a major way.

Having had their initial nitrogen at the start of the month, our OSRs will be receiving their second split of N imminently, with around 50kg/ha held back for mid-late April for the greatest support through pod fill.

All our winter cereals have had their first split of N too, with the second and backward wheats and barleys responding particularly well to their early attention.

Manganese deficiency has been far more evident than normal in many wheats. To such an extent that we had to give crops that were really suffering pre-T0 attention for the first time this year.

As planned, in all but the most badly infected crops of Oakley, we’ve deliberately held back on our T0s until now to keep the gap to T1 to a maximum of four weeks. Fluquinconazole seed-treatment has really helped here. Indeed, we’ve yet to see established yellow rust in any treated crops.

Mildew has really subsided, so our T0s are based on rust-active triazoles plus clorothalonil, with morpholine where yellow rust is especially problematic.

I’m keeping very flexible on T1 recommendations at this stage, as three weeks with little rain and temperatures of 17-18oC could see us in a very different place from where we are now. Last year we had fantastic results from both pyraclostrobin and bixofen – for their effect on plant physiology as much as disease control. So, together with the prothioconazole we’ve used extensively in the past, they’ll certainly be strong contenders.