Dry Autumn Prompts Brome Alert

February, 2004 - Brome problems are set to mushroom this year if wheat growers are not very careful indeed, warn leading agronomists. One of the driest autumns on record meant limited stale seedbed opportunities, poor quality ploughing and slow, v

ariable wheat establishment; all ideal conditions for brome to survive and thrive. At the same time, the species mix appears to be changing, with meadow and soft brome, in particular, increasingly reported in addition to the more familiar barren brome.

"We’re definitely seeing more and more meadow and soft brome these days," pointed out ProCam Agronomy technical director, Dr David Ellerton. "To such an extent that they present as much of a challenge as barren brome in many parts of the country. And two dry autumns in a row mean we’re facing serious problems from all three species this spring.

"Last autumn’s prolonged 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 meadow and soft brome, which 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.

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

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."

While Dr Bulmer still sees barren brome as the biggest problem, he points out that a significant proportion of reported barren brome infestations are actually likely to be the more difficult-to-tackle great brome, for which it is easily mistaken. He also reckons both meadow and soft bromes are becoming more widespread.

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, which also has a wider application window and greater tank mixing flexibility."

While all three agronomists insist that anyone who has brome in their wheat must tackle it firmly this spring, they are adamant that no-one should just rely on chemical control. Instead, they advise a careful programme of planned year-round management based upon accurate mapping of specific brome problems. "You must know what sort of brome you have and where, so you can plan your control strategy for maximum effectiveness," stressed David Ellerton, "Also, make sure you design your autumn herbicide programme to avoid ALS sequence restrictions."

"Maintain the best possible combine and field equipment hygiene to minimise seed spread," advised Bob Bulmer. "Maximise pre-planting stubble control opportunities too, delaying drilling wherever necessary. Avoid low seed rates and early drilling to ensure highly competitive crops from the outset. Really use your OSR break to make the most of residuals. And, where the problem is particularly serious introduce beans or even spring cropping into the rotation."

"Brome is undoubtedly a growing and changing challenge for many," concluded Nick Myers. "It may be a problem of modern, high intensity cereal systems, but it need not be a problem if you know your enemy and tackle it decisively."