The 2025 planting season started in earnest with somewhat drier conditions than usual. Water management has continued to be the theme this season which has caused some crops to start natural senescence early.
With this in mind, what is the best desiccation strategy this season?
We find out from FMC’s Commercial Technical Manager Antonia Walker, who specialises in potatoes.
Desiccation Decisions
“With the continued dry conditions we are experiencing both north and south of the Scottish borders its very clear that potato crops, especially unirrigated ones have started the process of senescence a littler earlier. That said, there is still a requirement to desiccate and this can be executed by spray applications alone, or using the flail and spray methodology” says Antonia.
Carfentrazone–ethyl, known by the brand name Spotlight® Plus, is a PPO inhibitor and has been widely used for over 20 years.
“It’s a great option for potato desiccation, says Antonia, as there are many positive features of the product.”
“One key benefit is that Spotlight® Plus can be applied in dry conditions with no adverse effect on tuber quality, such as vascular browning. This is reassuring for growers, particularly when conditions have been so dry”.
How does Spotlight® Plus work?
Spotlight® Plus is a PPO inhibitor (Protoporphyrinogen oxidase). This enzyme is essential for chlorophyll production and photosynthesis.
The inhibition of this enzyme results in highly reactive molecules that attack and destroy lipid and protein membranes.
Symptoms occur within one to two hours after exposure, appearing first as water soaked foliage, which is followed by browning (necrosis) of the tissue. Symptoms will appear most quickly with bright, sunny conditions at application and necrotic spots are sometimes surrounded by a reddish coloured ring.
Antonia recommends that applications of Spotlight® Plus are applied from mid-morning, to mid – afternoon during bright sunny conditions. This is essential for the breakdown the leaf membrane, thus killing off the foliage.
To Flail or not to Flail?
Desiccation decisions will be based on primary factors including variety choice and end market and storage requirements. For example, a crop destined for seed production will need a different desiccation strategy than a determinate second early variety or a late bulking non-determinate main crop variety.
Other factors also include soil type, physiological age of the seed tuber, planting date, planned harvest date, nitrogen management, and irrigation.
“There is a lot to consider, and growers need to take the time to contemplate what is the best strategy for them to maximise yield potential at the end of the season” says Antonia.
FMC’s advice it to have a minimum interval of seven days between applications of Spotlight® Plus. However, in certain situations, for example in seed crops, this interval may need to be reduced to five days. In non-flail desiccation programmes, following up after five days can be more effective than leaving it for seven days.
“It is important to use your eye and assess the growing conditions carefully” advises Antonia.
For flailed crops, flail to a height of 15 - 25cm and leave for 2 days before applying the first application of Spotlight® Plus at 1.0L/ha. This gives the target crop time to shed any additional leaves to ensure a good coverage. If any regrowth occurs, a follow up application can be made of 0.6L/ha after five to seven days.
Keep water volumes high
When applying Spotlight® Plus, it’s important to keep water volumes high. Antonia recommends a minimum of 300L/ha, However, the optimum is 450L/ha, which enables good coverage of the product throughout the canopy.
“Don’t be shy, it is essential to use a high rate of water to ensure a good coverage and maximize efficacy. Recommendations should always be above 300L/ha of water with the optimum being 450L/ha” advises Antonia.
“It is important to monitor crops after applications have been made. “This is to see if any regrowth has occurred, as a follow-up of Spotlight® Plus can be made after five to seven days”.
Key features of Spotlight® Plus
- Spotlight® Plus is a contact acting effective pre-harvest haulm desiccant
- It requires no aquatic buffer zone
- Built in wetter technology
- 7 day harvest interval
- Can be used on both seed and ware crops
- Maximum individual dose of 1.0L/ha (60g carfentrazone-ethyl / ha), with any follow up application, not exceeding 0/6L/ha (36g carfentrazone-ethyl / ha)
- Excellent at preventing regrowth
- Backward and forward-facing nozzles are recommended for best results
- Compatible with many blight fungicide products (see FMC website tank mix list) https://ag.fmc.com/uk/en/compatibilities
“Growers have been using the product for several years now, and I can confidently say that Spotlight® Plus is the leading stem desiccant on the market”, concludes Antonia.