1.0 l/ha REGLONE can be extremely effective at opening up a crop canopy
With the bulk of second earlies being harvested imminently and with maincrops to follow thereafter, this update focuses on desiccation and how to get the best out of Reglone.
Appropriate desiccation is not only fundamental to the manipulation of tuber size, but in a year such as this - with high levels of blight (Phytophtora infestans) - it is imperative that swift, effective desiccation takes place. If not, regrowth could lead to blight getting in at the last hurdle. As mentioned in previous updates, the widely acknowledged increased aggression of particular blight strains (or at least ability to infect a crop at lower temperatures) should be particularly front-of-mind in a season such as this. Protracted desiccation will increase the risk of more tubers becoming infected.
When should desiccation begin?
Clearly this depends on what market you are growing for. To a certain extent it will also depend on the variety being grown. Dry matter is an obvious consideration too, so growers must always consult with their customer as to what the requirements are.
Whilst first earlies are generally ready for lifting in June/July; second earlies July/August; and maincrop August onwards, the density of the haulm at knock-down will partly determine how long the interval is between desiccation and lifting. An actively growing crop will most likely take longer to reach skin-set than one which is reaching its natural senescence point. The earlier a crop is desiccated in relation to its natural maturity, the longer skin set takes. Crops lifted prior to skins setting properly are more prone to damage. Furthermore, the longer tubers are left in the ground the more they become susceptible to black dot, black scurf and other tuber diseases such as dry rot in warm weather.
It may be that this year desiccation takes place slightly later than usual, because planting was delayed for some due to wet conditions in the spring.
What is the interval between burning off and lifting?
A crop that is suffering from blight infection should not be lifted for at least 14 days from the first application of a desiccant to prevent contamination of the tubers.
There is no harvest interval for REGLONE, but if tubers are due to be stored then leave a period of at least 14 days to allow skin set prior to lifting.
What rate of REGLONE should be used?
Split dose Reglone applications provide flexibility to achieve the most cost effective options tailored to individual crops. A SMART test should be completed to assess the correct application options for REGLONE [note that even in the event of a SMART test fail, Syngenta will support the use of 1.0 l/ha of REGLONE for the first application, as long as it is not used in conjunction with any other desiccant at this first timing].
The initial application should be between 1.0–2.0 l/ha, according to the SMART test result, followed by 2.0–4.0 l/ha at least five to seven days later. Leaving this interval is important as it will provide time for more effective defoliation and, therefore, leave more of the stem exposed to be targeted at the second timing. With a maximum total dose of 5.0 l/ha, effective desiccation of even the most vigorous and actively growing crops is enabled, with the option of a three spray programme if needed e.g. 1.0 l/ha fb 3.0 l/ha fb 1.0 l/ha.
What is the optimum water volume to use?
Trials have shown that a minimum water volume of 200 l/ha should be used. This is appropriate for crops that are already starting to senesce or as a follow-up T2 or T3 application where split doses are used. The initial spray on a dense-haulmed crop that is still actively growing will benefit from a higher water volume. In this instance 300-400 l/ha is more appropriate. Angled nozzles should also be used to gain the best level of penetration at each timing (more so than air induction). These include the Syngenta Potato nozzle, Defy and Defy 3D nozzle.
What about flailing in conjunction?
Growers have the option of flailing before/during or after a REGLONE application (the SMART test should still be followed). If using the flail before applying REGLONE, aim to leave 15–25 cm stem height to minimise the risk of flail contact with the soil surface and damage to tubers and equipment. The remaining stem can be effectively killed off with REGLONE applied at 2.0–4.0 l/ha after three to five days when green leaf material has died back. Trials have shown up to 50% increase in work rate and 30% reduction in fuel costs from applying REGLONE at 1.0–2.0 l/ha, around five days prior to flailing.
Using REGLONE before flailing will initiate skin set and slow tuber bulking. By removing the mass of green leaf the flail can then pass through faster, using less fuel and also reducing the risk of spreading disease.
REGLONE can be used to good effect on its own or in conjunction with a flail.
What other considerations are there?
If you have used a nematicide, be sure to adhere to the harvest interval as stated on the label. For example, NEMATHORIN has a 119 day harvest interval period – this relates to 119 days from application to either desiccation or green top lifting. Desiccating before the 119 day period is up, even if harvest takes several weeks afterwards, is not permitted.
It is also advisable, particularly in a high disease pressure year such as this, to include a fungicide at desiccation which has activity on zoospores. SHIRLAN does just this, helping to prevent infected foliage from spreading disease to tubers.
If growing for seed it is also important to maintain control of virus caused by aphids until haulm destruction.
- Follow contract requirements (check if unsure)
- Remember to adhere to nematicide harvest interval period
- When using REGLONE, follow the SMART test
- Consider inclusion of a fungicide if blight pressure is high
- If using flail, REGLONE can reduce fuel cost and risk of blight spread