Although the use-up period for CIPC is currently unclear, this autumn/winter is likely to be the last when it can be used to treat potatoes in store.
If CIPC were to be used next autumn, it could cause significant stewardship issues due to its persistence, said Adrian Cunnington, head of crop storage research at Sutton Bridge Crop Storage Research at the Whole Crop Marketing trials day near Hull.
“If we applied it and then lost approval it could lead to all sorts of problems. The MRL is expected to be 10ppm for 2019/20. It would normally drop on withdrawal to the LoQ (limit of quantification) but there is a case being made in Brussels for a temporary [higher] MRL as CIPC hanging around for 15-20 years is not uncommon.”
Regarding alternative sprout suppressants, Mr Cunnington said maleic hydrazide is expected to feature as a significant part of sprout suppression regimes and that in The Netherlands and Germany, new volatiles are being used alongside it.
Non-chemical methods such as improving store temperature control and using the natural dormancy of potatoes could help reduce sprouting, he says. “We need to be using the natural dormancy of the potato more to our advantage.”
Alternative chemical options to CIPC are £3.50-£4.50/tonne more expensive, said Mr Cunnington. “Spearmint oil is applied as a hot fog. It is a very volatile chemical. The more exchange of air in a store, the more risk there is of losing it to the outside of the building and reducing its effectiveness.”
In The Netherlands, growers had reduced the amount of external air exchange taking place by looking at store venting to reduce CO2. If there is a move to more mechanical cooling such as refrigeration, slightly higher levels of CO2 could be tolerated, said Mr Cunnington.
“There is a school of thought that high levels of CO2 give poorer fry colour but this is not well proven. We are looking at whether we can do more work in this area. I am not totally convinced that we need to vent stores to the extent we have vented them in the past.
Looking ahead, DMN (1-4sight) (dimethyl-naphthalene) has shown promising results in trials, particularly combined with maleic hydrazide, said Mr Cunnington. “It has been in commercial use in The Netherlands for three years. Most processors are expecting to move to it but it isn’t here yet. It is very volatile so external ventilation will need to be limited where it is used. If it is approved, uptake for processing potato storage is expected to be significant.
“When it comes through, orange oil is likely to be targeted at the fresh market as a top up to refrigeration.”