Stay Flexible To Tackle Serious Brome Threat

February, 2004 - Build sufficient flexibility into your spring spraying programme to tackle a grass weed threat which is poised to mushroom this year, wheat growers have been advised.

Last year’s exceptionally dry spring played havoc with early-applied herbicides. And one of the driest autumns on record meant limited stale seedbed opportunities, poor quality ploughing and slow, variable wheat establishment; all ideal conditions for brome to survive and thrive.

"Brome control last autumn was almost non-existent," stressed ProCam Agronomy technical director, Dr David Ellerton. "Which is why so much brome is developing so strongly within so many wheat crops – aided, in many cases, by their slow and patchy establishment.

"The prolonged autumn drought, in particular, led to delayed and even less consistent ploughing than normal on the one hand and few, if any, decent Roundup-treated stale seedbeds on the other," he observed. "It also resulted in decidedly variable pre-em performances. So a lot of barren brome seed escaped either burial or chemical control.

"The dryness also played into the hands of the meadow and soft brome which we’re seeing very much more of these days. These species need a period of ripening on the soil surface before they will germinate readily and be vulnerable to pre-em treatment. The ripening happened, but poor pre-em activity meant they too were carried over relatively unscathed."

Farmcare agronomist, Dr Bob Bulmer, responsible for the Co-op’s 85,000 acre arable business, agrees that this year’s conditions have been ideal for a weed of high intensity wheat systems like brome.

"Brome is better adapted to modern cereal growing than almost any other grass weed," he explained. "More wheat in the rotation, more winter drilling, earlier sowing, lower seed rates, less total inversion tillage, and autumn weed control regimes that selectively eliminate other grass weeds all make life a lot easier for it. Add to this an autumn which prevents good cultural or chemical control and you have a potent mix.

"All the more so as we know from independent studies that, under competitive conditions, wheat yield losses of 0.80 t/ha from infestations of just 5 brome plants/m2 rise to well over 2 t/ha with 20 plants/m2."

So what can be done to prevent brome in its various forms really taking hold in this challenging season ? ProCam technical agronomist, Nick Myers identifies three valuable chemical weapons for growers this spring – the specialist brome-killer, sulfosulfuron (Monitor); the couch and brome herbicide, propoxycarbazone-sodium (Ethos); and the new broad-spectrum graminicide, mesosulfuron + iodosulfuron.

"All three herbicides have ALS sequence and following crop restrictions, so they need to be planned into the programme and rotation with care," he warned. "However, they are all good at tackling brome as well as being active against a range of other grass and broad-leaved weeds.

"If I had bad across-the-board grass weed problems I’d probably go for mesosulfuron + iodosulfuron. Be warned, though, it’s not cheap. Ethos would be my choice if I had brome and black-grass infestations and could get in early enough. And, if I wanted to hit brome and tackle cleavers, I’d pick Monitor.

"Monitor also stands out for its particularly wide application window and greater tank mixing flexibility," Nick Myers added. "The fact that it can be applied anywhere between GS13-39 of the crop proved invaluable last season. It allowed growers to wait out the drought before spraying to achieve effective brome control in a season in which those forced into earlier spraying by narrower windows had very disappointing results."

"Brome undoubtedly poses an acute threat for many wheat growers this season," insisted David Ellerton. "They must adopt a zero tolerance policy to the weed because of the damage it will do and the extent to which populations will build-up if left unchecked. And they would be well-advised to maintain the greatest overall flexibility in their spring spraying programme to counter the threat – preferably without the extra expense or hassle of a separate field operation."