Plenty of potato pointers
10 May 2002
Plenty of potato pointers
Visitors to the BPC Potato Storage Event at
Sutton Bridge Experimental Unit found plenty of
practical advice. Louise Impey reports
CIPC alternatives
ALTERNATIVE sprout suppressants that work alone or with CIPC should help growers meet the new maximum residue level for CIPC when it is introduced later this year.
"CIPC is being supported in the EU by two companies and it is expected to get Annex 1 listing soon," says Harry Duncan of the University of Glasgow. "But German producers can no longer use it, so there is understandable nervousness in this country."
Dimethyl-napthalene (DMN) is one or two years off registration in the UK and is already in successful use in the US, says Dr Duncan. "It gives results comparable to CIPC and can improve skin finish."
Close relation di-isopropylnapthalene (DIPN) is also promising and has been used successfully in mixtures with CIPC. "Again, there are plans to introduce it to the EU."
Other options include carvone, hydrogen peroxide, irradiation and ethylene. "The jury is still out on most of these. Some are too expensive, others have consumer acceptability issues or give variable results. But there will be niche market uses."
Variety testing
POTATO variety testing has been revamped to include greater industry involvement so its views can be included in the results, says research and development director Mike Storey.
"A good example of this is that we will now be including the determinancy of every variety. That will allow growers to take advantage of any fertiliser savings."
NIAB and SAC have been contracted to do most of the work, but satellite sites belonging to merchants and grower groups are also being involved.
"Market needs and growing conditions are being addressed," adds Dr Storey. "And the system will recognise varieties can behave quite differently in Scotland, due to its different day length."
Costs have been held at £120,000/year. The new list will be available for use for 2003 plantings.
Twelve new varieties entered trials this year, the highest number for some years, says James Trounce of NIAB. "Of these, four are crisping varieties, the rest pre-pack or ware. The declining market sector is loose skinned, first earlies."
Tackling rubbery rots
CONDENSATION in store and favourable conditions at harvest are to blame for last years widespread rubbery rot, says pathologist Jeff Peters of SBEU.
Warm, wet weather let the disease into the harvested crop, then infected tubers went into store during a warm period, so any resulting condensation allowed the soft rots to spread quickly.
Harvesting tubers with good skin set is a priority to avoid a repeat, he says. But that has to be balanced with harvesting early when soils are dry and temperatures are warm. "If theres a conflict, skin set should take precedence."
Removing rots and cull piles is also important, as is avoiding damage. "Make sure you plant Erwinia-free seed at the outset. A test will give you the total counts."
Condensation can be reduced by minimising temperature gradients in store, using insulation and ventilation, while air leaks and warm/cool air mix also need minimizing, advises Dr Peters. "Get into the store and take a look. You will be able to spot where condensation is occurring.
Seed producers
MAKE sure you have enough positive ventilation capacity to dry tubers rapidly and continue ventilation for at least a week, seed producers were urged by SACs Stuart Wale.
"Two days is not enough, either for early lifting or where cold, wet tubers have to be dried after a late harvest."
Drying within hours and sustaining the dryness until tubers are in a steady condition is a requirement of a ventilation system, says Dr Wales. "It is vital to stop any infection at the critical early stage after lifting. Ventilation for two days wont be sufficient in many situations."
Potato blight
DUTCH growers have responded to the loss of tin-based sprays by improving their attention to detail and timeliness in blight spraying programmes, reports pathologist Wilbert Flier of Plant Research International in Holland.
"Its made them become much more vigilant earlier in the season. And its encouraging an integrated approach to tuber blight management."
Eliminating early infection sources and maintaining foliar blight control throughout the season are essential, says Dr Flier. "Theres more use of resistant varieties in Holland too – some have foliar blight resistance and others have tuber blight resistance. The challenge is to combine these two characteristics."
Mancozeb is another blight product that can no longer be used in Holland. "The choices for Dutch growers are Shirlan (fluazinam) or Ranman TwinPack (cyazofamid). So this year will be tough."
David Marris of BASF told growers that Ranman fits into a blight programme just before the last two tin applications. "It protects against foliar and tuber blight. But it is a protectant only, so growers shouldnt view it as a tin replacement."
• For more on the BPC Event, turn to Machinery p84. *
Maintaining foliar blight control throughout the season is essential, according to William Flier.
Changes to potato variety trials will take more account of industry views, says BPCs Mike Storey.
New sprout suppressants will help growers meet a tighter CIPC limit, says Harry Duncan.