Withthe three key pathogens which cause ear blight disease present in most crops,growers need to pay careful attention to weather forecasts as the T3 timingapproaches, advises Dr Philip Jennings of The Food and Environment ResearchAgency (Fera).
Henotes that the latest site assessments are potentially worrying. F. culmorumis splashing around on most Feras monitoring sites, with the perithecia of F. graminearumis also being found at a number of sites, and likely to be maturing afterrecent rain. Microdochium is present on stems, particularly on crops in lighter,drier soils, although levels are lower on heavier soils or where standing waterhas been issue.
Asever, the over-riding issue this year will be the weather at flowering. Ifconditions are right at flowering, infection is a big risk, almost irrespectiveof inoculum pressure. So keep an eye on weather forecasts. If you dont get aspray on in time, youll never get infection out of the ear, he adds.
Withall three pathogens threatening yield and quality, and F. graminearum and F. culmorumproducing harmful mycotoxins, the need for robust control is clear he says.Last years extremely testing conditions showed prothioconazole was again theproduct of choice, especially where Microdochium was present, since otheroptions do not reduce it, notes Dr Jennings.
Andlast season also showed how crucial dose and timing is. He points out that manysprays were too late and even where follow up sprays were used, it would haveonly controlled later infections. Fullrate triazoles gave six days of protection, typically three days either side ofthe application date, which delivered good control if flowering started andfinished in that period. But where flowering was extended, follow-up sprayswould have been needed to prevent further infection.
Oneglimmer of hope around this years severely delayed crop development could bethat crops rush through flowering very quickly. If growth stages are subject toa concertina effect, one well-timed ear spray should suffice. But rates need tobe robust, he stresses.
Whilstreduced rates may not reduce the period of protection, they certainly reduceeffectiveness, Dr Jennings adds. When it comes to Fusarium Id say dont playwith rates. Theres not much point using anything below half rate.Three-quarter rate isnt bad, but full rate is best, and that means a full-rateof triazole. Some formulations contain a reduced ratio of triazole, so even ifthe full product rate is used, you might still only apply half rate triazole,which really isnt enough, he warns.
Thisyear, even if flowering is completed quickly, it may not start very early, andmaybe not until potentially warmer and more thundery weather in late June oreven early July. This could add to the disease pressure and raise issues aroundrainfastness and spray windows. It is certainly true that if conditions aregood for ear disease, theyre invariably bad for spraying, concludes DrJennings.