POTATO GROWERS with backward crops need to be patient when desiccating to ensure effective haulm kill, experts have advised.

Many crops are two to three weeks behind normal this year, due to drier weather and more immature crops may take extra effort to knock down, said Scottish Agronomy’s Eric Anderson.

More vigorous growing varieties such as King Edwards, some Maris Piper, Hermes, Slenay and Cara can be particularly difficult to kill, he said.

“You’ve got to be patient when using acid alternatives such as Reglone [diquat] or Spotlight [carfentrazone-ethyl]. Give crops at least 10 days for the maximum effect.”

Where crops are still growing and bulking up, growers should not leave it too long before desiccation, added Andrew Farley from Agrownomics.

“Crops with low tuber numbers will bulk up quicker – which could push size over the premium baker or pre-pack bands. Delays in lifting if weather turns bad will increase the risk of Black Dot and other skin diseases developing.”

He suggests using a split-dose of Reglone to stop tuber bulking and initiate skin set.

The speed of skin set dictates harvesting date and reduced levels of Black Dot or Black Scurf, said Mr Anderson. “Growers need to look at what’s going on under the ground, rather than just the leaf canopy.”

Bruising appears to be a particular problem in crops harvested so far, he noted. This could be due to dry weather during desiccation and he believes levels could be similar to 2003.

Total GB clearance to September 2 was estimated at 20,200ha (16.3% of total), compared to 26,000ha (19.8%) last year, according to latest British Potato Council figures.