ERGOT FUNGUS was less troublesome in cereals last season than in 2003, but it hasn”t gone away. That was the unequivocal message for growers at an HGCA meeting near Wantage, Oxon, last week.
So with tests confirming that fungicides offer little defence against infection, other steps must be employed to minimise rejected grain deliveries, urges ADAS pathologist Peter Gladders.
“There”s no quick fix from spraying, and there is potential for it to be aggravated by grass margins and beetle banks.”
Indeed there is some evidence that late ear washes can add to the problem by removing otherwise competing disease, he says.
Ergot fruiting bodies, from which the initial infection arises, replace grains in cereal and grassweed ears. But they are much shorter-lived than those of sclerotinia in oilseed rape, generally surviving only a year. The latter can persist in the soil for up to a decade.
Burying shed ergots by ploughing and introducing a year”s break can do much to remove the problem. Unfortunately, unlike sclerotinia, they are toxic, says Dr Gladders.
That means there are strict limits on the amount permitted in grain for seed and feed (see ergot standards box).
It is possible to clear the bulk of ergots from an infected sample. “But it”s often very difficult to get the last bits out.” Indeed it was almost impossible to produce ergot-free seed in 2003, he notes.
Several aspects of modern cereal growing favour ergot, says Dr Gladders. A wide range of weed grasses act as infection sources. Most growers know that blackgrass is a prime candidate, and herbicide resistance clearly doesn”t help.
“Many, though, may not realise that annual meadowgrass is also often thick with it.” The ergots are much smaller and less obvious, he explains.
“Annual meadowgrass can flower every month of the year and you can find ergots in it every month of the year.
” Meadow foxtail, which also flowers early, is another potential threat, whereas ryegrass, cocksfoot, oat grass and Yorkshire fog are less so.
In the light of this and the introduction of extra field margins under SFP cross-compliance, more work is needed to determine acceptable mixtures for sowing, says Dr Gladders.
“We are also keen to find out how far ergot spreads into crops from the margins.”
Current thinking is that secondary infection, spread by physical contact between the honeydew of infected ears and healthy ones and perhaps by insects, is quite localised. So a 0.5-1m (20-40in) unsown strip could provide sufficient barrier.
Minimal cultivations, which leave infective ergots on the soil surface, tend to increase the ergot problem.
Secondary tillers tend to get more. So anything leaving gaps in crops, such as tramlines and poor establishment from low seed rates, can exacerbate ergot levels.
“Low seed rates could be a bad move unless you are particularly careful with your nitrogen management,” he says.
Open-flowering cereals, notably Rialto wheat but also Option more recently, tend to be more susceptible to infection.
Hybrid barley breeders face a big problem where the male sterile parent is at particular risk.
Apart from starting with clean seed, preferably treated with a fungicide dressing, and correcting copper deficiency, pinpointing ergot infection is the most useful practical step growers can take, suggests Dr Gladders.
“Ask yourself where you have ergots and harvest it separately. Generally it”s worst in blackgrass patches.
” Running down the tramlines with slightly wider tyres just before harvest to flatten the secondary tillers and avoid combining them could also be useful, he says.