Target foliar disease with T3 fungicides

Topping up foliar disease control is likely to be the priority with T3 ear sprays in wheat this season, rather than fusarium control, agronomists are suggesting, despite last year’s much higher grain mycotoxin levels.

Targeting fusarium control specifically required growers to go earlier than the traditional foliar disease top-up ear spray, Hutchinsons’ Dick Neale told Farmers Weekly.

“The best time is when the ears are just out (GS55-59), rather than GS65+, so growers need to decide what they are really after.”

That meant fungicide programmes could be condensed, with flag leaf sprays only just applied, and wheat ears already 15-20% emerged, he admitted. “That maybe the inconvenient truth, but if you want to get fusarium control you will need to go then.

“Growers are kidding themselves if they think they are getting fusarium control if they spray later when the anthers are hanging off the side of the crop. Any ‘control’ then is only because the fusarium was never there in the first place.”

Fungicide rates also needed to be higher where fusarium was the target, with typically 75-100% doses required of a fusarium-active azole for the best control, he said. In comparison a wider range of products were available for a foliar disease top-up spray, and, in general, rates could be less than half rate.

Weather around flowering, crop potential, fusarium risk and orange wheat blossom midge risk all had to be taken into account when making the decision as ears emerged, he suggested.

“In general it looks more like it will be a foliar disease top up year than a year to specifically target fusarium,” he said.

Background levels of fusarium were quite low, according to latest Crop Monitor reports, and while the weather forecast for the flowering period included some rain it was not “soaking wet”, he explained. “It is looking like a fairly normal year.”

Several days of wet, muggy weather or the possibility of orange wheat blossom midge attack could change the decision, however, he suggested. “There is an increased risk of orange wheat blossom midge now following the rain we’ve just had, and it is quite opportunistic. If you’re having to go in for that you might as well use a fungicide.”

Lincolnshire TAG agronomist Andrew Wells agreed T3 timing could be driven by what happened with orange wheat blossom midge. “The pre-flowering fusarium timing coincides with blossom midge, so if we need to spray for that it will get a fungicide.”

That was likely to be the end of next week, beginning of the following one, he said on Tuesday [26 May], giving a two-week gap from flag leaf sprays.

He wouldn’t be advising growers did everything at that timing, however, he stressed, although anything with milling potential would be targeted. “We need to do everything we can to get a low result.”

Norfolk independent agronomist Mike Thompson was advising his growers to target foliar disease control rather than fusarium this season, he said.

“Aiming to control fusarium is a bit too hit and miss with fungicides, particularly when you have to use a three-quarter dose of triazole. You just don’t get good enough control regularly enough to justify it,” he said.

“You can do everything right and still be over the DON mycotoxin limits. So this year we are going to revert to the traditional margin calculations and top-up septoria control using 0.75 litres/ha of Firefly (prothioconazole + fluoxastrobin) as the starting point.”