21 February 1997

Beet finds new weapon

Last season was a tough one for sugar beet herbicides. Edward Long discovers how a new product fared in its first commercial year

DEBUT, launched last year by Du Pont, is the first sulfonylurea herbicide approved for use on sugar beet.

Its contains triflusulfuron-methyl, and is also the first significant new broad-leaved weed-killer for use on sugar beet in 20 years.

It has a different mode of action from existing herbicides and combines contact and root activity with a short residual life. It is recommended for use in early post-emergence tank mixes.

Shaun Watson was forced into using more contact-acting sprays than normal last season, due to cool weather and a lack of seed-bed moisture.

"Our weed control strategy in sugar beet is based on a pre-emergence approach," says Mr Watson, who grows 91ha (228 acres) of beet for John Davies Farms on 440ha (1100 acres) of light and medium loam soil at Swancote Farm, Swancote near Bridgnorth, Shrop-shire. "The pre-emergence application for 1996 was Pyramin, with Betanal Progress, Venzar, Debut and Goltix used post-emergence."

Debut was used to control cleavers, a growing problem on his lighter fields. Root crops are grown with cereals in a three-year rotation. Cleavers are normally tackled with Starane (fluroxypyr) in cereals. But Debut now provides another chance to hit the troublesome weed.

There was enough soil moisture in early April for the pre-emergence sprays to work. But the weather turned cold and dry between mid-April and mid-May, so follow-up post-emergence treatments were severely compromised. On some fields spraying was delayed by over a month. "It was so cold and dry it would have been a waste of time applying residual post-emergence sprays. We ended up using more contact herbicide than ever before in three post-emergence treatments instead of the normal two," says Mr Watson.

Due to lack of suitable spraying days, a 24m sprayer was used instead of the normal 12m machine.

"After applying Debut we noticed a transient yellowing of the beet. But the crop grew out of this in four to five days. The product had a massive impact on cleavers, even in cold conditions. It also controlled annual nettle, late fat-hen, speedwell, and knotgrass at a larger growth stage, and helped control volunteer potatoes, which was a bonus."

"Debut performed well in a difficult spraying season. If cleavers appear I would use it again," comments Mr Watson.

Faced with difficult-to-control fools parsley in beet grown on old permanent pasture land a Norfolk grower turned to Debut last year.

"Weeds are not a worry in beet elsewhere on this farm. But the 25-acre problem field had been grass until 1978 and it has inherited a legacy of troublesome weeds," says Simon Burridge, who grows 18ha (45 acres) of beet on the familys Laurel Farm, Pulham St Mary, near Diss.

"We used Debut because we were also targeting volunteer rape, which is expensive to control, and knotgrass and charlock."

The idea of using the new herbicide came from Mike May of the locally based Morley Research Centre. It was applied twice, first on Apr 25 with phenmedipham (Betanal) and metamitron (Goltix), and again in early May with phenmedipham and lenacil (Venzar).

Spraying conditions were far from ideal, with little soil moisture. Poor conditions wrecked the performance of the pre-drilling tri-allate (Avadex) treatment, so fluazifop-P-butyl (Fusilade) was sprayed as back-up. Annual grass weeds and early broad-leaved types were removed by chloridazon + ethofumesate (Spectron).

"There was little residual activity in the soil following the earlier herbicides," says Mr Burridge. "But Debut suppressed fools parsley. In a more normal year it might have knocked it out completely. Our beet was suffering from drought stress, so did not grow fast enough to suppress weeds to help the herbicide. But the treatment was worth applying."

The only drawback is the meticulous tank-cleaning needed after using Debut. "If I can get away without having to use it in future I will due to the laborious and time consuming job of cleaning out the sprayer," says Mr Burridge. &#42

Shaun Watson found Debut kept his beet crop clean. The product worked well on cleavers and other weeds, including volunteer potatoes, he says.

A clean start, but problem weeds can soon rear their heads. In Simon Burridges case, fools parsley was the main trouble last year. Slow beet growth reduced the crops weed smothering effect, but he reckons he achieved reasonable control with Debut.


&#8226 Transient beet yellowing.

&#8226 Works well on cleavers, fools parsley and other weeds.

&#8226 Some volunteer potato control.

&#8226 Sprayer cleaning takes time.