Spring 2018 – T0 or no T0?
T0 or no T0 – it’s an obvious question to ask given recent cold snaps, and we have received a number of enquiries on the topic.
It is important to be equally mindful of what can go wrong if a T0 spray is omitted as you are of the few £s per hectare you could save. We have been in similar situations before. So, think back to what happened if you’ve cut back on a T0 in the past.
Factors worth taking into account
Ultimately, the decision needs to be based on individual field situations and local knowledge, but it’s worth remembering what a T0 is designed to achieve:
- To reduce overwintered inoculum – especially where rust is concerned. Failure to control early rust build-up can result in ‘chasing’ the disease for the rest of the season. Using a T0 in a rust situation has been shown to deliver a clear yield response. Active rust is still being found at our trials sites, so check your crops.
- To provide leeway in case of a delayed T1 spray (GS32, leaf 3 emerged) – for example, due to the weather. That’s quite possible if we have a showery season. Wet weather not only makes travelling difficult, it also encourages Septoria to spread
Remember, too, that recent cold weather won’t only have slowed down disease development, but also the development of the crop.
T0 (or any other timing for that matter) should be driven by crop growth stage, NOT a fixed calendar date. T0 should be targeted at leaf 4 emerged.
This approximately coincides with GS31 (depending on drilling date) and usually occurs around late March to early April. This year, however, it could be towards the latter end of that window, which could have a beneficial effect.
How a later T0 can help
If T0 application timing falls early in the year, it can ‘force’ T1 to be applied too early (in trying to maintain a sensible interval between treatments). This, in turn, can make the critical T1-T2 interval too long.
By comparison, if the T0 timing falls slightly later, it’s less tempting to bring the T1 spray forward – meaning all the spray intervals from T1 onwards are better for keeping Septoria in check.
In conclusion, a winter wheat T0 fungicide currently remains as relevant as it was at the start of the season. It’s just that the calendar date may be a little later than ‘normal’.
Remember also that T0 is when first PGR applications (affecting rooting) are being made. So, you could be getting the sprayer out anyway.