Quick crop desiccation sets tuber size

Potato crop harvesting is underway in the West Country and South Wales, with growers seeking early price bonuses for high quality tubers with clean skins after a short growing season, reports Syngenta South West Area Manager, Duncan Woodward. Tuber size management is crucial to achieve the optimum tuber numbers in the premium pre-pack size, he advises.

"Desiccation timing is all important in stopping tuber development at precisely the right point. The fast action of Reglone to fully desiccate leaf and stems (above) can effectively stop further tuber bulking and prepare for a clean lift at harvest," he says. "New guidelines for growers now give the chance to use Reglone on all crops and under all soil conditions."

With the current hot weather and dry soils, Mr Woodward highlights that growers planning to use a Reglone application of more than 1 l/ha on actively growing crops must always undertake a SMART test (Soil Moisture Availability for Reglone Treatment). "Providing there is sufficient moisture at tuber depth to create a ball of soil, growers can use up to the full rate," he reports. "But if it is too dry and the soil crumbles, the initial dose should be limited to 1 l/ha."

The initial low-dose application will trigger senescence, initiate skin set and start to halt further tuber bulking (above showing before and after initial 1 l/ha Reglone). A second application after five to seven days, once senescence has started, can be at 2 - 4 l/ha as required to complete the crop desiccation.

"On big leafy early crops we would always tend to advocate this split-dose sequential approach. It removes the bulk of the leaf with the initial application and opens the crop canopy to target stems more effectively with the second treatment," he adds. "In dense crops application with the angled Syngenta Potato Nozzle and using a higher water volume of 400 l/ha for the initial application will further help target sprays onto lower leaves and stems; second applications can be at 200 l/ha water volume, and still using the angled nozzle."

With the current very high costs of tractor fuel associated with flailing big crop haulms, Mr Woodward reports growers are increasingly looking at total Reglone desiccation. "At the very least, an initial 1 or 2 l/ha Reglone treatment a week before the planned flail operation will remove the leaf and create brittle stems - enabling far faster, cleaner and more cost effective flailing, with less risk of spreading diseased green leaf material," he advised.

Mr Woodward reminds growers that where harvesting is delayed and significant regrowth or weed cover has occurred requiring a further Reglone treatment, the SMART test should be repeated before application. "A 25% increase in the label rate recommendation for Reglone means growers can now use a total of 5 l/ha to complete the desiccation of even the most vigorous crops."