Bruising season for spuds
Bruising season for spuds
By Robert Harris
BRUISING, rather than blight, is the main problem affecting this seasons potato crop. Disease levels are lower than feared, though they are still causing agronomists concern.
With 25-30% of maincrop lifted, yields are similar to last years levels of 45-50t/ha (18-20t/acre), says Anglian Produces technical director Simon Bowen. "But that disguises a large variation. There are some very good and very poor crops about."
Careful grading will pay well. A high level of defects reduce graded output, and good quality material is likely to be scarce, he explains. "Once poorer quality produce has been sold prices should pick up."
Bruising caused by dry soils is widespread in East Anglia, comments Dr Bowen. Soil is difficult to keep on harvester webs, reducing its cushioning effect.
It is less of a problem in Lincs, being mainly restricted to Marfona, Saxon and some Estima crops, says David Nelson of Branston Potatoes. "We had two to three inches of rain in early September. Conditions are almost ideal." However the rain has caused some growth cracking, he notes.
Bruising is common in Yorks, notes Graeme Byers of the Finningley-based Higgins Group. "Growers must pay attention to harvesters and the grading line to minimise impacts."
Blight can be found in most areas, but generally at lower levels than were feared. "Its not too bad in East Anglia. Farmers were very aware of it and reacted accordingly," says Chris Marshall, MBM agronomist based inCambs.
Blackleg may be more a problem, suggests Bury St Edmunds-based ADAS agronomist Colin Smith.
"We have seen in it some susceptible varieties like Agria and Morene."
However, the disease struck early, so many tubers have rotted in the ground, says Dr Nelson. But crops containing half rotted tubers, which can infect healthy ones, are best sold early, he adds.
Three weeks of dry weather have helped reduce blight and blackleg problems in Yorks. "We recommend at least four weeks between burning down and harvest to allow a good proportion of diseased tubers to disappear," says Mr Byers.
Internal rust spot, caused by a breakdown of tuber cell walls due to calcium deficiency exacerbated by hot August weather, is also common in some crops, especially Piper and Estima, notes Dr Bowen.
Black scurf is starting to hit crops, especially those that have been burnt off for a month or more, he adds. Growers with high levels of infection in pre-pack varieties should consider switching to processing markets, says Mr Marshall.
Slug damage is a major worry on heavier soils, especially in Piper, warns Mr Smith. "Growers should lift affected crops as quickly as possible, then try and grade damaged tubers out."
Atotal of 320mm (12.5in) of rain in June, July and August brought blight spray intervals down to five days, but helped this 17ha (42 acres) of Marfona set-skin potatoes at LCAHFarms in Lincs to achieve close to 70t/ha (28t/acre) with over 60%baker size, reports manager Tony Smith.
LIMITINGDAMAGE
• Irrigate with 0.5-1in 24 hours before lifting to reduce bruising, unless foliar blight active.
• Avoid big impacts on harvester and grading line.
• Pinpoint problem areas by sampling from different harvester and grading line locations. Place tubers in hotbox or airing cupboard overnight, then slice to assess damage.
• Consider electronic potato test if serious bruising found.
• Store crops at risk of blight or blackleg separately, or sell now.
• Inspect stores daily for first month.
• Ensure tubers are dry when stored. Cure quickly. Reduce temperatures of pre-pack material as soon as possible.