4 August 1995

Cold storage best for silver scurf

COLD storage has proved more effective than current fungicides for controlling silver scurf in potatoes in a trial run by Westward Arable Centres at Torpoint in Cornwall.

Agronomist Owen Jones told WACs annual potato open day at Antony Pedigree Farms, Torpoint, that a comparison of varieties and storage conditions in 1993 showed Estima was more susceptible to silver scurf than Maris Piper. Both varieties had less disease in a cold store than an ambient store with no temperature control.

In 1994, trials were established using Dutch Estima seed with 57% of tubers showing over 50% silver scurf infection at planting on April 18. Before planting some seed was treated with Fungazil (imazalil), some with Monceren (pencycuron), and some had no treatment.

The crop was lifted on October 5 and when graded a week later half was treated with Storite (thiabendazole).

Where no fungicide was used pre-planting, more than 65% of the untreated tubers were badly affected by silver scurf after two months in an ambient store. Those which had been Storite-treated were little better.

Both lots fared better in the cold store, but again there was no clear benefit from Storite.

Where Fungazil went on pre-planting, Storite initially reduced silver scurf in ambient store, but appeared less effective later. Both treatments remained below 20% incidence in cold storage.

Using Monceren pre-planting gave a similar result to Fungazil-silver scurf under ambient storage and much less under cold storage.

Mr Owen has also studied the NIAB variety trials on the site and claims there are some differences between varieties in resistance to silver scurf. He felt growers could benefit from more knowledge of varietal resistance. However, NIAB is not assessing varieties for silver scurf resistance currently.