Potato growers are facing into a harvest season with the loss of one of their most important crop management tools. From 4 February this year, the use of the chemical active diquat is no longer permitted on EU farms.
Diquat was widely used as a pre-emergence herbicide and as a pre-harvest crop desiccant. It lost approval in Europe due to concerns regarding operator exposure, risk to birds and the potential consequences of long-term use on groundwater and aquatic wildlife.
While alternative pre-emergence strategies are effective, there are no direct alternative haulm desiccants available which can achieve the same results.
Used as a desiccant, diquat was very quick-acting and effective on leaves and stems. It allowed growers to effectively manage crop foliage and blight pressure, harvest dates, tuber size and improve harvest ease.
The alternative product on the market, Spotlight Plus (containing the active carfentrazone-ethyl), is slower, taking around three to four weeks to act, and is also relatively poor on leaf desiccation.
Why is this such an issue?
For many growers, diquat has been the main tool in potato haulm destruction for decades. With no direct alternatives, its loss triggers a host of knock-on effects for main, salad and seed crop production.
Using carfentrazone-ethyl, crops will generally be harvested later due to a slower senescence period. A longer growing season will likely lead to increased disease pressure and fungicide spend. A later harvest also brings an increased risk of poorer ground conditions.
The loss of diquat poses a big issue for potato growers in Ireland
Poor harvest conditions increase the cost and energy involved with harvesting and can also cause problems further downstream, from grading through to storage. Soils may be prone to more damage in a later harvest or through the mechanical destruction of haulms using flails. Flails also increase the risk of disease spread and pest attack.
In short, the loss of diquat poses a big issue for potato growers in Ireland which is exacerbated by our moist climate and the varieties grown here.
However, this is an EU-wide issue and two countries have already issued emergency authorisation for the use of the active this season. The Irish Farmers Journal reviewed the notification documents sent to the European Commission for two of these countries, Finland and Slovenia. Greece and Hungary have also issued approval.
Finland
Finland granted emergency authorisation for diquat for use on a range of vegetable and fruit crops. The authorisation for potatoes is split into two periods this year – 1 May to 15 June and 10 August to 22 September.
Diquat was the key potato desiccation tool for growers for many years.
In the country’s notification document the potato crop is described as having a very high economical value for Finnish growers and the industry.
It reads: “The desiccation of the stems and leaves before harvesting is very important to ensure the quality of the potatoes during the storing period. Otherwise the quality losses in storage can be very high.”
The document refers to the slow-acting nature of carfentrazone-ethyl and the risk of late blight infections. On mechanical haulm destruction, it states there isn’t enough machinery available in the country to do this and it wouldn’t be possible in the wet conditions which are experienced there.
To avoid risks to bystanders/residents, a 10m buffer zone and the use of 90% drift-reducing nozzles will be applied. Following label instructions will be sufficient to avoid risks to human health and the environment, the document outlines.
Slovenia
Slovenia also granted emergency authorisation of diquat for use on potatoes, seed alfalfa and red clover crops between 1 June and 28 September this year.
Its notification document also cites the high economical value of the potato crop for Slovenian growers and the industry.
In Slovenia there are no authorised plant protection products for desiccation of potato haulms. It argued that the mechanical destruction of haulms isn’t appropriate as it often results in damage to the tubers and increases the chance of disease infections.
Complying with the instructions for use is sufficient to avoid risks to human health and the environment
Slovenia’s mitigation measures against the risk to bystander/residents include a 15m buffer zone and use of 50% drift-reducing nozzles. Complying with the instructions for use is sufficient to avoid risks to human health and the environment, it states, adding that the product can be used only by professional users with PPE.
Ireland’s response
Emergency authorisation of diquat is still a live issue in Ireland. It is understood that emergency authorisation has been sought by the IFA and the Irish Potato Federation. Growers have also been proactive. Three weeks ago local members of Donegal IFA met in Burt, Co Donegal, with Inishowen-based TD Charlie McConalogue under strict social distancing conditions.
Speaking to the
Irish Farmers Journal, Donegal potato grower Charlie Doherty (left) said the aim of the meeting was to inform McConalogue of the role and the importance of the active in modern potato production and how no direct replacement exists.
“Donegal is as far northwest as you’ll go. We simply don’t have the climate for alternative desiccation strategies,” Doherty said. “Spotlight is poor on leaves and is generally too slow to act, leaving the crop prone to blight and pest attack. In a wet autumn like 2019, haulm topping simply won’t work and this applies for the whole country”.
Furthermore, the recent dry weather and risk of a late flush of nitrogen as well as the lack of training for alternative desiccation methods due to COVID-19 justifies emergency authorisation this season he added.
However, grower’s hopes of emergency authorisation this season suffered a set back last week. In a parliamentary questions session, Minister Creed stated “Due to the risks identified during the recent assessment process, it is not proposed to issue emergency approval at this time”
Potato growers are facing into a harvest season with the loss of one of their most important crop management tools. From 4 February this year, the use of the chemical active diquat is no longer permitted on EU farms.
Diquat was widely used as a pre-emergence herbicide and as a pre-harvest crop desiccant. It lost approval in Europe due to concerns regarding operator exposure, risk to birds and the potential consequences of long-term use on groundwater and aquatic wildlife.
While alternative pre-emergence strategies are effective, there are no direct alternative haulm desiccants available which can achieve the same results.
Used as a desiccant, diquat was very quick-acting and effective on leaves and stems. It allowed growers to effectively manage crop foliage and blight pressure, harvest dates, tuber size and improve harvest ease.
The alternative product on the market, Spotlight Plus (containing the active carfentrazone-ethyl), is slower, taking around three to four weeks to act, and is also relatively poor on leaf desiccation.
Why is this such an issue?
For many growers, diquat has been the main tool in potato haulm destruction for decades. With no direct alternatives, its loss triggers a host of knock-on effects for main, salad and seed crop production.
Using carfentrazone-ethyl, crops will generally be harvested later due to a slower senescence period. A longer growing season will likely lead to increased disease pressure and fungicide spend. A later harvest also brings an increased risk of poorer ground conditions.
The loss of diquat poses a big issue for potato growers in Ireland
Poor harvest conditions increase the cost and energy involved with harvesting and can also cause problems further downstream, from grading through to storage. Soils may be prone to more damage in a later harvest or through the mechanical destruction of haulms using flails. Flails also increase the risk of disease spread and pest attack.
In short, the loss of diquat poses a big issue for potato growers in Ireland which is exacerbated by our moist climate and the varieties grown here.
However, this is an EU-wide issue and two countries have already issued emergency authorisation for the use of the active this season. The Irish Farmers Journal reviewed the notification documents sent to the European Commission for two of these countries, Finland and Slovenia. Greece and Hungary have also issued approval.
Finland
Finland granted emergency authorisation for diquat for use on a range of vegetable and fruit crops. The authorisation for potatoes is split into two periods this year – 1 May to 15 June and 10 August to 22 September.
Diquat was the key potato desiccation tool for growers for many years.
In the country’s notification document the potato crop is described as having a very high economical value for Finnish growers and the industry.
It reads: “The desiccation of the stems and leaves before harvesting is very important to ensure the quality of the potatoes during the storing period. Otherwise the quality losses in storage can be very high.”
The document refers to the slow-acting nature of carfentrazone-ethyl and the risk of late blight infections. On mechanical haulm destruction, it states there isn’t enough machinery available in the country to do this and it wouldn’t be possible in the wet conditions which are experienced there.
To avoid risks to bystanders/residents, a 10m buffer zone and the use of 90% drift-reducing nozzles will be applied. Following label instructions will be sufficient to avoid risks to human health and the environment, the document outlines.
Slovenia
Slovenia also granted emergency authorisation of diquat for use on potatoes, seed alfalfa and red clover crops between 1 June and 28 September this year.
Its notification document also cites the high economical value of the potato crop for Slovenian growers and the industry.
In Slovenia there are no authorised plant protection products for desiccation of potato haulms. It argued that the mechanical destruction of haulms isn’t appropriate as it often results in damage to the tubers and increases the chance of disease infections.
Complying with the instructions for use is sufficient to avoid risks to human health and the environment
Slovenia’s mitigation measures against the risk to bystander/residents include a 15m buffer zone and use of 50% drift-reducing nozzles. Complying with the instructions for use is sufficient to avoid risks to human health and the environment, it states, adding that the product can be used only by professional users with PPE.
Ireland’s response
Emergency authorisation of diquat is still a live issue in Ireland. It is understood that emergency authorisation has been sought by the IFA and the Irish Potato Federation. Growers have also been proactive. Three weeks ago local members of Donegal IFA met in Burt, Co Donegal, with Inishowen-based TD Charlie McConalogue under strict social distancing conditions.
Speaking to the
Irish Farmers Journal, Donegal potato grower Charlie Doherty (left) said the aim of the meeting was to inform McConalogue of the role and the importance of the active in modern potato production and how no direct replacement exists.
“Donegal is as far northwest as you’ll go. We simply don’t have the climate for alternative desiccation strategies,” Doherty said. “Spotlight is poor on leaves and is generally too slow to act, leaving the crop prone to blight and pest attack. In a wet autumn like 2019, haulm topping simply won’t work and this applies for the whole country”.
Furthermore, the recent dry weather and risk of a late flush of nitrogen as well as the lack of training for alternative desiccation methods due to COVID-19 justifies emergency authorisation this season he added.
However, grower’s hopes of emergency authorisation this season suffered a set back last week. In a parliamentary questions session, Minister Creed stated “Due to the risks identified during the recent assessment process, it is not proposed to issue emergency approval at this time”
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