Rhizoctonia is running rife in cold, wet potato seedbeds and hampering crop emergence this season. The effects of stolon pruning and scarring are clearly evident on affected tubers in untreated areas of Amistar split field trials, reports Syngenta Field Technical Manager, Roger Blyth.
He added that with a high proportion of the UK crop is still to be planted and little prospect of an imminent resumption in field work on saturated soils, the risk of attack on tubers is high. “For those crops still to go in, Amistar application at planting could provide essential protection against soil pathogens during establishment and prevent further delays in the crops’ growth.”
The legacy of the severe spring infection could result in increased levels of Black Scurf on tubers at harvest, he warned. Rhizoctonia stem and stolon pruning during establishment can also trigger greater secondary tuber initiation, leading to inconsistent tuber size and maturity at harvest - which would impact on processing and packing quality, as well as overall profitability of the crop.
The current conditions are also highly conducive to the Black Dot pathogen, which has historically been especially damaging on tubers harvested after a slow-growing, wet season. “This year’s later sown crop may need an extended growing season to bulk up, which will increase the risk. Reducing soil pathogen populations now is especially important in wet conditions, and will have a significant role in protecting tuber skin quality at harvest,” added Mr Blyth.
He said that inspection of crops in Amistar trials in Yorkshire, Nottinghamshire and Suffolk last week (10 May 2012) had all revealed the extent of Rhizoctonia infection. “It was clear to see that plants in the treated areas of the field were emerging consistently, compared to just odd plants in the untreated rows.
“Inspection of the seed tubers showed evidence of severe lesion damage and scaring on stolons and sprouts being attacked by Rhizoctonia in untreated areas, whilst stems in the Amistar treated areas were growing evenly and cleanly.” All trials would be taken through to harvest and the results assessed for yield and tuber quality, he added.
