On-farm hygiene plays a major role in mitigating threats from difficult to control beet pests and diseases. CPM reports.
“The major risk is where you’re growing beet next to a field that had beet the previous season, especially if it’s a split field or where there are no hedges.” DR ALISTAIR WRIGHT
By Mike Abram
Arguably, most of the difficult agronomic pest and disease challenges in sugar beet production can be reduced through one of the oldest basics in farming: excellent on-farm hygiene and use of related cultural control methods.
“It’s risk management,” suggests Stephen Aldis, head of field operations for BBRO. “These techniques can be deployed very successfully, but their role in creating security for following crops isn’t always considered. I’m not sure growers always realise the threat that poor on-farm hygiene poses.”
Good on-farm hygiene helps with many of the agronomy challenges beet growers face, stresses Dr Alistair Wright, head of crop protection for BBRO.
That includes virus yellows, which is the greatest disease threat currently to the beet crop. “It’s long been recognised that one of the highest risks is poor hygiene allowing carryover of aphids and/or virus to the following crop,” he says.
Beet clamps, self-propelled loader runs, spoil heaps or groundkeepers can act as a reservoir for virus infections or homes for overwintering aphids, and should be destroyed in a timely fashion, ideally several weeks before drilling starts next spring, adds Stephen.
That can be done through either using glyphosate or cultivation. “While weather will have the greatest influence on virus yellows risk, on a field-level, avoid creating conditions where aphids can move easily from beet or other hosts to newly emerging beet crops.
“Try to avoid building clamps on fields that are going to be beet next year – if it’s unavoidable, the area should be ploughed down after to bury any beet remnants.”
On-farm hygiene also helps with two other emerging threats to sugar beet production: cercospora and beet moth.
For the former, which is being found in virtually every field this autumn, its residue management, particularly of leaf material that is key, points out Alistair. “That firstly comes down to good topping of the beet. You don’t want leaf material being carried into clamps because that’ll leave a concentrated area of inoculum for future years.”
Ploughing after the beet crop or areas on fields where clamps have been located away from the beet field will reduce disease carryover. “If minimum tillage is used the residue won’t be buried and is free to sporulate in following seasons,” adds Alistair.
“The major risk is where you’re growing beet next to a field that had beet the previous season, especially if it’s a split field or where there are no hedges. The spores can be blown from one area to another.”
Literature suggests cercospora spores, which are relatively large in size, don’t travel more than a few metres, with barriers such as a tree belt – and to a lesser extent a hedge – limiting spread. “But we do know they can travel longer distances if they get taken up into the air, so it’s important to maximise the distance between beet this year and beet next year.
“Return spoil from where it came from, as it’ll potentially contain many spores. Even if the clamp or Maus line is on a field that won’t be beet next year, the spores can be blown to next year’s field. We often see the first stage of cercospora damage comes from where a Maus line was.”
Less is known about carryover of beet moth, which has been a problem in some of this season’s beet crops, suggests Alistair. “It’s localised in severity, but you can find it across East Anglia. Some crops are unaffected and yielded well, in others the canopy has gone leading to growers to lift earlier for yield preservation.”
BBRO is due to publish its beet moth research strategy this winter, which will include looking at the role of on-farm hygiene and the carryover of moths, highlights Alistair. “Potentially, moths may overwinter as larvae in any root remnants left in fields or as pupae in soil within their cocoons, which we think are quite protective.
“We know from literature they survive at very low temperatures, so we can’t rely on a hard frost to kill them like we do with aphids.”
Instead, the research will look at alternative ways to make life difficult for the pest, which will include comparing ploughed with non-ploughed areas of heavily infested crops. “Logic suggests that a little moth, only 1-2cm long, will find it difficult to crawl through 15-20cm of soil with its wings intact if they even make it to the surface.”
Emergence traps will test whether the moths emerge, while new pheromone-based traps with cameras that use AI to identify the pest, will be used to compare emergence when the moths reach nearby fields. “The new traps allow us to monitor on a daily basis rather than weekly,” comments Alistair.
However, more is known about beet cyst nematodes. “It’s important to consider risk and correct variety choice for BCN, but also carryover of cysts into future crops and around the farm,” he says.
“Like beet moth cocoons, BCN cysts are very protective of the eggs inside. Eggs are protected for up to 20 years, surviving rolling or any mechanical action in the soil.”
That makes it easy to transport the cysts to other areas of the field or across the farm on any machinery, he adds. “You can go from a small foci infection to a massive patch in a field in a relatively few passes of a cultivator.”
Cysts can also blow on the wind, move on your boots or with livestock, and are hosted by a whole range of crops and weeds. “If you’ve had it in one field, it’s likely to be across a whole block of land.”
While that makes it difficult to stop spread, practicing good on-farm hygiene has a place, albeit one with practical limitations, raises Alistair. “Best practice would be to clean down machinery as it moves in and out of every field. That’s clearly not a workable suggestion, but think about whether you can work a block in one go and then clean down machinery.”
Rotation and use of cover cropping has to be carefully thought about with BCN, as well as virus and other pest threats. “There’s a range of risks; radishes and mustards can be fantastic BCN hosts, but also potentially a useful management tool.”
Growing BCN-resistant class one species could reduce populations by around 20-30%, proposes Alistair, although based on laboratory tests, breeders claim higher reductions. “While they are more expensive, growers should be requesting BCN-resistant class one varieties.”
Class two BCN-resistant brassicas are also available but are less resistant, suggests Alistair. “They’ll probably maintain populations at the starting level, while susceptible varieties or species can boost populations by a factor of 10 or 20.
“If you’ve used a susceptible brassica in your cover crop before beet, think about destroying it as soon as possible to limit further multiplication, bearing in mind scheme restrictions.”
He adds that other cover crop species can be hosts of virus yellows or aphids – for example, phacelia, forage rape, red clover and vetch. BBRO’s cover crop guide is a useful source of information about the risks, concludes Alistair.
The guide (bbro.co.uk/publications/cover-crop-guide/) also provides details about risks for other pests and diseases, such as slugs and wireworms, where on-farm hygiene also plays an important role in control.
This article was taken from the latest issue of CPM. Read the article in full here.
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