Thursday, 23 July 2020
Three storage webinars held in June were an opportunity to hear from the team of storage experts at Sutton Bridge Crop Storage Research, as well as cleaning and agronomy specialists.
To complement the webinar sessions, now available to watch back, we have answered some frequently asked questions around key topics of potato storage post CIPC.
CIPC legacy: what we know about the temporary MRL (tMRL)
Q1. If a tMRL threshold hasn’t been approved by the end of the use up period of 8 October 2020, will the MRL revert to the Limit of Quantification?
A1. The Maximum Residue Level (MRL) for CIPC is currently 10 mg/kg. This threshold will remain until a new level has been set.
Q2. When does the tMRL supercede the existing MRL?
A2. We don’t yet know this. It is anticipated that this will be discussed, and a decision may be reached, when the EU SCoPAFF (Standing Committee on Plants, Animals, Food and Feed) meet in September 2020.
Q3. What is the likely tMRL for CIPC expected to be?
A3. It is anticipated to be around 0.3 - 0.4 mg/kg.
DMN registration process & emergency use
Q1. If DMN does get emergency approval, is it likely to have any label restrictions for example a cattle feed restriction?
A1. The Chemicals Regulation Division may consider a feeding restriction is necessary if an emergency approval is granted.
Q2. If DMN is released for emergency use, how much product would that be? Would it be enough for all the Industry?
A2. Emergency approval is not full approval. If granted, use would be restricted to very limited market situations.
Store management post-CIPC
Q1. One regular grower concern when advised to keep stores closed after treatment with mint oil (BIOX-M) is possible CO2 build up. Have CO2 levels been measured as part of storage trials?
A1. CO2 can build up in closed stores. We are undertaking trials to measure the impact on fry quality. We expect some detrimental effect so it will remain important to find ways to extract CO2 without losing a lot of volatile chemical. We don’t anticipate an effect of 48 hours store closure on fry quality but this will also depend on the equipment used to carry out the application.
Q3. When looking to build a new store, can boxes from stores with a history of CIPC application be used?
A3. Ideally, new boxes would be better. If old boxes have to be used, make sure they are aired outside over the summer to reduce contamination levels.
Q4. How can the loss of volatile sprout suppressants be minimised in stores cooled with ambient air?
A4. The best thing to do is to widen the difference on the cooling system slightly (say 2.5-3C instead of 2), to bring in air which will provide more cooling and reduce flushing.
Store cleaning & CIPC decontamination
Q1. How can you tell if cleaning has been effective enough to minimise CIPC residue in the various store fabrics?
A1. It is difficult to be sure. Testing samples from foam walls, concrete floors or other building substrate is not recommended because it is the residue value of potatoes in the store that will be measured for MRL purposes. Our results indicate that residue values will comply with the proposed tMRL.
It’s important to remember that in order to comply with the MRL, it is the stored crop that is measured. Results indicate that we will be able to do this by just by 'dry' cleaning stores, but we may need to wash later, but this won't become apparent until after a couple of seasons.
Q2. Why are you discouraging the use of water to clean stores?
A2. We are concerned that CIPC would find its way into watercourses. Also, CIPC is not very water soluble. Boxes for example can be aired outside and this has been shown to reduce residue levels.
Q4. What is the proper procedure for disposal of contaminated dust from stores?
A4. Dust hoovered up from the body of the store can be disposed of in the usual way (skip), it is no more contaminated now than in previous years. More care will need to be taken with solid material from ducts or under application ports. This should be disposed of by a contractor.
Maleic hydrazide in-field application for sprout control
Q1. Should growers be carrying out Maleic Hydrazide (MH) residue tests? If so when is the best time?
A1. That would be useful, MH application can be tricky so understanding when an application has worked well and when it hasn't would be useful. Residue levels are very static during storage so timing is not important.
Q2. I have heard MH is more effective later in the storage season rather than earlier. Is this correct? Is it worth treating crop planned for December movement?
A2. No that is not the case, MH is effective as a sprout suppressant throughout the period a crop spends in store. If in-store treatment is necessary, MH should be considered, especially if moving the crop around Christmas or just after.