New product approvals needed to halt carrot losses, agronomist warns

The carrot industry faces "potentially massive" losses to viruses this year due to lack of control options, a leading carrot agronomist has warned.

Root necrosis - image: FERA
Root necrosis - image: FERA

Howard Hinds of Root Crop Consultancy says this scenario is the result of three factors coinciding; discovery of a new virus, a new vector and further restriction on the use of crop protection products.

He estimates that 15 per cent of last year's crop, with a farm gate value of £20m, was lost to carrot viruses, and warns this figure can only increase due to insufficient chemical controls.

"Last year even with two Biscaya (thiacloprid) sprays, Aphox (pirimicarb) and pyrethroids we were stretched to breaking point," he said.

"Cruiser (thiamethoxam) seed treatment recently gained off-label approval, which is welcome as it will help with early season aphid control. But carrots are lost from the new Aphox label, and the newly discovered vector the peach-potato aphid is potentially resistant to all other approved insecticides except Biscaya."

Meanwhile another vector, the willow-carrot aphid, "has already been caught in suction traps in the east, more than a month earlier than normal", he added.

Hinds said he is now hoping that Bayer's ketoenol insecticide Movento (spirotetramat) will be given urgent approval for use in carrots.

"This would certainly be a big help, but we need at least two further new products as well. When we were focusing on willow-carrot aphid we were mainly concerned about early to mid season control. Now with peach-potato aphid to take account of too, crops could need protecting from April into September."

The new carrot virus and vector were discovered during AHDB-funded projects led by Fera's principal plant pathologist Adrian Fox. One of the new viruses found was carrot yellow leaf virus (CYLV), strongly linked to the presence of root necrosis, and transmitted by three species of aphids, willow-carrot aphid, peach-potato aphid and willow-parsnip aphid.

"Most carrot virus management has focused on controlling willow-carrot aphid as this has been traditionally linked to early season transmission of yellow fleck and the motley dwarf complex," Fox said. "This finding raises important questions about strategies for season-long control of viruses."

He suggested that an integrated strategy of alternative management methods is needed, now that the limited number of chemical control options make season-long control difficult to maintain.

"These could include the use of fleece or netting as a barrier to infection, IPM approaches to increase populations of natural predators and use of aphid monitoring programmes to time spray applications as accurately as possible," he said.

"The effectiveness of some of these approaches still needs to be confirmed but anything that reduces viral burden on crops is likely to reduce losses."

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