Transplants are ‘programme-killers’
Transplanted black-grass is a serious danger to even the best-planned weed control programme, an eastern counties agronomist has warned.
Both pre-em and post-em treatments will fail if growers do not deal ruthlessly with the transplanted black-grass problem, says Richard Peake of Harlow Agricultural Merchants.
"Stale seedbeds are a most important tool," he maintains, "and this year - in contrast to the previous season - we have ideal conditions for them. Wipe out as much black-grass as possible before putting the crop in the ground."
Once beyond one leaf, Mr Peake explains, the black-grass control achieved from pre-em treatments tails off. "And when growers are forced into post-em treatments - which could happen this year if Crystal supply doesn’t resolve itself - transplanted black-grass becomes too big.
"That has knock-on effects on the ability of later-applied products such as Atlantis," he points out, "with implications for resistance management, to say nothing of potential yield loss and seed carry-over."
Transplanted black-grass - when cultivations loosen germinated and chitting seedlings, but fail to kill them - is a threat, Mr Peake believes, because of the current soil moisture content. "Although it’s been relatively dry during September, the five inches of rain that fell during August has kept enough moisture in the soil to ensure that black-grass seeds are thriving - despite the ’official’ predictions for ’moderate’ dormancy this season."
Given the Crystal issues, and the state of seedbeds, Mr Peake’s advice is to delay sowing winter wheat and use applications of Gallup (glyphosate) to combat black-grass. "Either wait, or beware of post-emergence flufenacet applications."
Stale seedbeds are an embedded feature of many growers’ cultural control measures, but Mr Peake says farmers have too much expectation of their ability to ’cultivate out’ the black-grass.
"Several times, I’ve taken a customer into a field where he’s not planning to spray off because there’s no black-grass. I always say, ’Walk on another 50 yards and turn around to face the sun, then tell me again.’ The direction of the light makes a fundamental difference, especially when the sun is low.
"The biggest sin is underestimating the quantity of black-grass seedlings and then overestimating your ability to control them. That’s why glyphosate - at least one application and preferably two - must always be used."
Modern formulations of quality glyphosate products such as Gallup present growers with no requirements for extra wetters or other additives, says Mr Peake, but he suggests growers should opt for a water conditioner.
"In many areas of the country, water has a pH above 7, yet glyphosate works better in slightly acidic water," he explains. "It’s to do with the way it binds with cations in the water; adding the water conditioner to the spray tank before the glyphosate ’binds-up’ the rogue cations, rather than allowing them to lock-up the glyphosate.
"The final point to note is spray quality. Remember, you’re spraying a bare surface with some black-grass as small as a human hair, so wind speed is crucial. Your target is tiny, so fine droplets are a must - yet the temptation of air-induction nozzles must be resisted, as this will deliver coarser droplets."
