Survey highlights blackgrass problems
Survey highlights blackgrass problems
Too many winter cereal growers fail to control blackgrass effectively, according to a survey conducted by Novartis among 65 farmers from the main blackgrass areas of England.
Nearly a third – 30% – are not satisfied with control levels, says the companys Andy Pigott. Increasing seed return, with most respondents blaming the straw burning ban, is the main reason. "Clearly some growers are not getting on top of the problem."
Almost a quarter did not recognise that seed-beds should be of medium to fine quality, he notes. "Too many push on with drilling without giving a thought to blackgrass control."
Early ploughing followed by pressing conserves moisture and, in a damp season, encourages a flush of weeds which can be chemically burnt off before drilling.
Discs and tines can then be used for final seed-bed preparation. "In dry, heavy soils power harrows leave a mass of cobbles on the surface. Moist, fine particles work their way down."
Blackgrass germinates in the underlying layer and roots deeply. Isoproturon, which chiefly relies on root uptake to work, can struggle to control the weed.
A good seed-bed promotes rapid, even crop germination. "A good crop is worth a herbicide. It is more able to compete." Weeds also germinate evenly – in rougher seed-beds they emerge from varying depths. Clods also break down slowly, releasing seed which can germinate through winter.
"Get it right, and most blackgrass germinates within a month of drilling. One well timed spray in late November or December can control it with no need for a spring overspray."
A quarter of the growers thought spring sprays were important, with almost half that number making it their main timing. But blackgrass grows quickly at that time of year due to warmer soils, increased day length and freshly applied nitrogen, says Mr Pigott. Resulting large, well-tillered plants are difficult to kill.
"Not only are growers losing yield, but they may have to pay for extra chemical and another spray pass as well."
Nearly half the respondents did not realise there are two types of resistance, target site and enhanced metabolism. "That in itself does not matter, but it is important to understand the mechanisms."
Target site resistance, where plants are resistant to fops and dims, remains rare, he notes. Most cases involve enhanced metabolism resistance, where plants show a partial resistance to a range of herbicides.
Early control is vital. In spring, plant enzymes are more active, so can detoxify chemical before it kills the plant, he explains. "But spraying the same population with straight clodinafop in the autumn can result in control of about 95%."
Just over half the growers – 53% – questioned the use of isoproturon in their control programmes, mainly due to its unreliability, says Mr Pigott.
"We tend to view it as avery cost-effective addition to stronger blackgrass products like Hawk. Adding 1000g/ha gives good broad-leaved weed andannual meadowgrass control, boosts activity against blackgrass and adds a further mode ofaction."
BLACKGRASS SURVEY
• 30% of growers dissatisfied with blackgrass control.
• 27% reckon seed return higher this season.
• 25% believe spring sprays important.
• 48% do not know resistance types.