10 April 1998

Early action helps maintain quality

LOW levels of internal rust spot have always been found in potatoes grown at L W Van Geest Farms in Spalding, Lincolnshire.

But last year far more tubers were hit. The main sufferers were varieties which received no routine foliar calcium, says farm manager, David Walker. "We started using Calmax about four years ago to help prevent storage losses," he recalls. "So it was only the two varieties which are sold straight from the field which did not benefit last season."

Tuber quality is important for the 182ha (450 acres) of pre-pack potatoes. "There is no doubt rust spot is becoming more widespread in this area. And the weather we experienced last year made it far worse."

Maris Piper, King Edward, Cara, Estima, Marfona and Fianna are all grown on the Lincolnshire farm, with only Marfona and Cara sold from the field. Maris Piper is particularly prone to rust spot, notes Mr Walker

He aims to get calcium on to the growing crop early. "We use a little-and-often approach. Every time we spray for blight, we add some Calmax. Although it does not completely eliminate the condition, it means we do not get rejections."

Cost is about £13/ha (£5.26/acre), he says. "It is not a big expense for a potentially high value crop and it is effective." Brassica crops also benefit. Both sprouts and white cabbage have had Calmax for the past 10 years.

"Without it, as soon as the crops are subjected to stress, they develop brown rings on the edges of the inner leaves, affecting both value and marketability," notes Mr Walker.

Little and early is how Spalding grower David Walker (left) uses anti-rust spot product Calmax. Calcium is something more growers are coming to appreciate as they pursue quality markets, adds Omexs Gidon Bahiri.