2013-06-19   facebook twitter rss

Effective Sclerotinia Control Achieved with Carrot Clipping

Sclerotinia is one of the most widespread and economically important diseases of carrots, affecting both yield and quality. It has been estimated that the disease could cause annual crop losses to UK growers in excess of £5million.

Problems arise when the carrot foliage ­ especially in commercial varieties such as Nairobi – flops over, or lodges, and becomes rotten creating an ideal warm, moist environment for disease development. The sclerotia, which have been dormant in the soil, will germinate under these conditions and spread into the foliage and crop bed causing plant and root death and rendering the carrots unsaleable.

The first clip should take place at the end of July, beginning of August just as the foliage is starting to lodge.

The first clip should take place at the end of July, beginning of August just as the foliage is starting to lodge.

“BASF has been investing in ways of improving Sclerotinia control for carrot growers using an integrated approach,” explains Rob Storer, BASF’s Speciality Crops Product Manager. “Working with Howard Hinds of Root Crop Consultancy Ltd and Wroot Water, who have manufactured a new three-bed system called the Wroot Clip Master 3, we have been carrying out trials for a few years and now find the efficacy is better than it was and the dataset much more robust.”

“The clipping system is a simple but effective cultural control method,” explains Howard Hinds. “The first cut, which should take place at the end of July beginning of August, provides the most benefit, with a second, if necessary, in early September. The foliage drops into the bottom of the wheeling where it dries to a brown mat. This creates a gap between the side of the carrot bed and dried up foliage so preventing disease infection spreading into the plant.”

“The Clip Mater 3 machine can operate at speeds of 10km/hour allowing 200-300 acres to be covered in a day. The discs rely on the forward speed of the tractor so it is quite a simple system with no hydraulics involved. The discs run a few inches into the soil and are positioned on the edge of the bed, away from the carrots. A pivoting action helps cope with any gradient there might be in the field,” explains Howard.

“Last year we conducted some semi-commercial trials. In each field half the filed was clipped and half left unclipped. As part of an integrated approach the crops underwent a spray programme including an early season spray of Signum. Results were very positive. Where the crop had been clipped we were getting 50% reduction in the amount of Sclerotinia and in one trial we achieved a 90% reduction in the disease. The best result appears to have been down to the timing of the clipping which took place just as the crop started to lodge but before the disease really became established.”

“Carrot growers need to adopt an integrated approach in the management of Sclerotinia in the field,” explains Rob. “They need to use the right chemistry at the right time, front loading with Signum early on and alternating with other products before the canopy covers over to reduce the risk of resistance. Then by adopting a cultural approach – the carrot clipper ­ the risk of disease spreading into the crop will be minimised. We also need to be looking at developing a decision support system to monitor disease incidence. We are currently working on this with The University of Warwick and ADAS and hope to have something in place next season via the BASF website to provide growers with a more informed approach to disease control in their carrot crops.”

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