Yellow rust, fusarium and loose smut should be on cereal growers minds as they consider seed
treatments this autumn.
AT A fifth of the cost of a foliar fungicide, seed treatments are still the most cost-effective insurance policy cereal growers can get.
However, decisions on seed treatments are often made without any prior knowledge of the health of the seed, points out ADASs Bill Clark: "Its rather like selling house insurance to someone without knowing where they live."
Knowing which diseases are present on your seed is the only way to make an informed choice about what rate of seed treatment to use, and more important which one, he says.
Nine times out of ten you may not need a seed treatment at all, says Mr Clark: "Most certified seed is probably clean enough to drill untreated," he says.
Ask your merchant for the test results carried out on the certified seed you buy, urges Mr Clark, and then make your decision on whether you actually need a seed treatment.
For home-saved seed the only way of knowing what diseases present a threat to your crop is testing. To test seed for all diseases would be too expensive, but NIABs Jane Thomas advises targeting the ones presenting the highest risk: "Look at crops carefully to find symptoms in the standing crop and target seed testing requirements based on the highest risks."
High risk diseases this autumn are obviously yellow rust, given this years epidemic. But fusarium could make an unwelcome comeback with the recent wet weather. Likewise loose smut in barley could be another disease to watch for, she says.
Leaf stripe is more difficult to predict – so much depends on the starting base of innoculum in the crop sown, explains Ms Thomas. NIAB tests on loose smut cost £48; leaf stripe and net blotch £62; fusarium £48.
One of the biggest problems on testing is turnround time between harvest and drilling. This year the NIAB seed testing department can expect up to 2,000 samples.
New technology currently available in the medical industry – multiplex DNA testing – will give a quicker turnaround on tests. It should be a more cost effective solution because it will enable several diseases to be detected with one test, explains Ms Thomas. However, it is still some way off from commercial reality in agriculture.
Until then what should growers do? Yellow rust is clearly a big issue and Baytan, with its foliar activity against the disease, is the logical choice. However, it is twice the price of the other standard treatments and with grain prices at £85/t and less, many wheat growers are asking whether it is possible to cut back on seed treatment rates reports Mr Clark.
Cutting seed treatment rates is the last place to start controlling variable costs, reckons Mr Clark. "If you get it wrong you risk losing the whole crop; if you get a foliar fungicide wrong you risk losing only half the yield," he says.
However, rates could be cut, but only if you know exactly which diseases are present and this comes back to testing. "Half rate Baytan will control yellow rust, but wont contain fusarium," he explains.