Article taken from the FarmBusiness, written by Heather Briggs
Despite some occasional heavy pressure this season, overall insect control in brassicas and carrots has been reasonably good, reports John Allan, vegetable technical team leader at Agrovista.
One big challenge was the diamond black moth that feeds on crops in the mustard and cole families, although growers were generally able to keep on top of the pest with the synthetic pyrethroid Bandu (deltamethrin) or Rumo (inoxaxarb).
“The larvae feed on leaves and stems of these crops, and can cause a great deal of damage if they aren’t spotted early enough,” says Mr Allan. “If infestation levels are high and not treated in time they have been known to eat the entire leaf, leaving only the vein.”
He says white fly (aleyrodes proletella), which attached all brassicas and is particularly difficult to control in curly kale and Brussels sprouts, has been a hot topic in some areas of the country.
“These pests leave a dew secretion on the underside of the leaf which can in turn develop a mould, affecting the look – and saleability – of the crop, particularly in kale where the leaf is saleable part of the plant.
“If infestations are high they also can make harvesting very uncomfortable,” he remarks, adding that harvest gangs often have to resort to using a dust mask to protect themselves from the white flies that emerge in clouds when disturbed.
“Generally speaking, the pest is quite well controlled with Movento (spirotetramat), as long as it is applied before the pest is on the plant.
“Because it is systemic – the insecticide is moved around the plant – it is only really effective which the plant is actively growing. The challenge this year has been the very dry spell in September when plant growth was quite slow, which meant that control was less effective.”
The situation with the mealy cabbage aphid could have also been difficult as it is controlled in the same way, but fortunately, Mr Allan says, high levels of this pest have not been observed so far this year. “Movento and Biscaya (thiacloprid) are both very useful controls.
“Biscayer, of course, is a neonicotinoid but, importantly, one that is not affected by the neonicotinoid ban and can still be used.”
One of the brassicas crop’s potentially most important pests, cabbage root fly (delia radicum), looked as though it could become a real menace in June, but thanks to use of Cyren (chlorpyrifos), growers were able to contain damage by drenching or spraying.
With increasing regulatory pressure on the approval and use of conventional chemistry the industry is looking to move away from the traditional means of control, so the use of biological controls could make a real contribution, observes Mr Allan.
“The nematode ‘Steinernema feltiea’ is looking to be a promising method of control for the future,” he says. “These predatory organisms are drenched into the base of the plant shortly after planting and before the larvae of the cabbage root fly emerge.
“They are effective at preying on larvae, but their activity on adult insects is limited, so timing of application is important.”
This season control of the most serious insect pest in carrots, the carrot fly, has been reasonably successful where seed has been treated with Force ST (tefluthrin) and the pyrethroid Markate (lambdacyhalothrin), he reports.
“Carrot fly occurs in several generations,” he says. “However, we have found the armoury has been really quite effective this season.”
Mr Allan emphasises the importance on keeping on top of the carrot willow-aphid to minimise the threat of viral infection of the crop with Parsnip Yellow Fleck Virus, both of which can cause severe losses from stunted roots.""
He advocates subscribing to the alert service provided by Plantsystems that uses an emergence model based on accumulated day degrees, giving a four-day warning of potential attack. “To get the most effective control you need to move in with Aphox (pirimicarb), Biscaya or deltamethrin as soon as you detect the aphids in the crop,” he says. “Therefore the alerts give you that bit of time so you can amend your work schedules as necessary.”
Last year’s warm soils in July and August led to an extended second generation of the carrot fly, so the third generation was slightly later.
Despite some occasional heavy pressure this season, overall insect control in brassicas and carrots has been reasonably good, reports John Allan, vegetable technical team leader at Agrovista.
One big challenge was the diamond black moth that feeds on crops in the mustard and cole families, although growers were generally able to keep on top of the pest with the synthetic pyrethroid Bandu (deltamethrin) or Rumo (inoxaxarb).
“The larvae feed on leaves and stems of these crops, and can cause a great deal of damage if they aren’t spotted early enough,” says Mr Allan. “If infestation levels are high and not treated in time they have been known to eat the entire leaf, leaving only the vein.”
He says white fly (aleyrodes proletella), which attached all brassicas and is particularly difficult to control in curly kale and Brussels sprouts, has been a hot topic in some areas of the country.
“These pests leave a dew secretion on the underside of the leaf which can in turn develop a mould, affecting the look – and saleability – of the crop, particularly in kale where the leaf is saleable part of the plant.
“If infestations are high they also can make harvesting very uncomfortable,” he remarks, adding that harvest gangs often have to resort to using a dust mask to protect themselves from the white flies that emerge in clouds when disturbed.
“Generally speaking, the pest is quite well controlled with Movento (spirotetramat), as long as it is applied before the pest is on the plant.
“Because it is systemic – the insecticide is moved around the plant – it is only really effective which the plant is actively growing. The challenge this year has been the very dry spell in September when plant growth was quite slow, which meant that control was less effective.”
The situation with the mealy cabbage aphid could have also been difficult as it is controlled in the same way, but fortunately, Mr Allan says, high levels of this pest have not been observed so far this year. “Movento and Biscaya (thiacloprid) are both very useful controls.
“Biscayer, of course, is a neonicotinoid but, importantly, one that is not affected by the neonicotinoid ban and can still be used.”
One of the brassicas crop’s potentially most important pests, cabbage root fly (delia radicum), looked as though it could become a real menace in June, but thanks to use of Cyren (chlorpyrifos), growers were able to contain damage by drenching or spraying.
With increasing regulatory pressure on the approval and use of conventional chemistry the industry is looking to move away from the traditional means of control, so the use of biological controls could make a real contribution, observes Mr Allan.
“The nematode ‘Steinernema feltiea’ is looking to be a promising method of control for the future,” he says. “These predatory organisms are drenched into the base of the plant shortly after planting and before the larvae of the cabbage root fly emerge.
“They are effective at preying on larvae, but their activity on adult insects is limited, so timing of application is important.”
This season control of the most serious insect pest in carrots, the carrot fly, has been reasonably successful where seed has been treated with Force ST (tefluthrin) and the pyrethroid Markate (lambdacyhalothrin), he reports.
“Carrot fly occurs in several generations,” he says. “However, we have found the armoury has been really quite effective this season.”
Mr Allan emphasises the importance on keeping on top of the carrot willow-aphid to minimise the threat of viral infection of the crop with Parsnip Yellow Fleck Virus, both of which can cause severe losses from stunted roots.""
He advocates subscribing to the alert service provided by Plantsystems that uses an emergence model based on accumulated day degrees, giving a four-day warning of potential attack. “To get the most effective control you need to move in with Aphox (pirimicarb), Biscaya or deltamethrin as soon as you detect the aphids in the crop,” he says. “Therefore the alerts give you that bit of time so you can amend your work schedules as necessary.”
Last year’s warm soils in July and August led to an extended second generation of the carrot fly, so the third generation was slightly later.