Two sprays better than one for sugar beet

Disease control is essential for new higher yielding sugar beet varieties to meet their yield potential, and with growers looking to boost late season yield in a mild, open autumn, the benefit of green leaf retention really pays dividends, according to Syngenta Technical Manager, Beth Hall.

In last year's independent trials at Broom's Barn in Suffolk, the Spyrale two-spray programme delivered an exceptional yield - breaking through the 100t/ha adjusted yield barrier.

"Drier summers have typically restricted root development, but a two-spray strategy minimises disease and helps retain green leaf to make better use of autumn conditions," reports Mrs Hall. "Extended lifting campaigns will allow the crop to compensate with late bulking."

Spyrale has shown outstanding control of all key sugar beet diseases, including powdery mildew, rust, and Ramularia. "The two-spray strategy is particularly strong against powdery mildew," she advises. "In the Brooms Barn trials the eradicant activity ensured initial symptoms of the disease had disappeared in later assessments, which no other treatment could achieve."

In a high pressure powdery mildew trial the Spyrale two-spray programme, applied in late July and late August, delivered 105 t/ha adjusted yield and a margin over input costs of £340/ha, compared to 96 t/ha and a margin of £185 from a single July application (Fig 1). Other independent trials by Armstrong Fisher in high rust risk areas demonstrated similar yield increases over untreated crops from both one and two-spray Spyrale programmes.

"BBRO estimates fungicide treated crops added around 16 tonnes of adjusted sugar per hectare between October and December last year," adds Mrs Hall. "Over the past two seasons, it reports two-spray fungicide programmes have proven cost effective for all but the earliest lifted crops. With longer campaigns expected from this autumn onwards, the benefits for growers could prove even greater."

Cercospora vigilance

The devastating sugar beet disease Cercospora was seen in a number of UK crops last year, warns Beth Hall. Experience in continental Europe indicates that once the disease takes hold, the spread across large areas of beet can be very rapid, leading to widespread defoliation and yield loss. Spyrale is extensively used on the continent for Cercospora control; the UK two-spray timing in July and August for rust and mildew is being further evaluated for activity on Cercospora in trials this summer.