Potato growers have sufficient alternatives to Chlorine IPC for long-term storage, according to storage research by Wageningen University & Research (WUR) Open Crops. The results of MD spraying in the field, supplemented with permitted space treatments, are at least comparable to traditional gases with chlorpropham agents.
The announcement that Chlorine IPC will not be renewed came as no surprise. Chlorpropham has been a topic of discussion for some time. In particular, the food safety authority EFSA gave a negative advice for the use as a sprout inhibitor, due to residues.
The European Commission ultimately decided to ban products containing this active substance as of 8 January 2020, with a use-up period varying per Member State. Incidentally, it is expected that Chlorine IPC can still be used for the next storage season.
For Arysta LifeScience, now part of crop protection manufacturer UPL, the uncertainty surrounding chlorpropham prompted testing of alternatives for sprouting inhibition. WUR Open Crops in Lelystad carried out a large storage test for this last year. This compares treatments with chlorine with, among other things, untreated and with only spraying with Royal MH, of which UPL is the authorization holder.
Researcher Joop Esselink of WUR explains that the potatoes of the test varieties Agria, Fontane, Innovator and Nicola were last assessed in mid-May for external germ, internal germ, storage loss and general quality. The potatoes are stored at 7 degrees with outside air cooling. Chlorine IPC was administered four times at a recommended dose.
Loss of moisture
The results show that the single application with MH scores the same as the germination inhibition with Chlorine IPC. The various objects were sampled five times from the end of February to mid-May.
‘At Agria, there was hardly any germ formation on the tubers during the entire storage period of the treated objects. The other three varieties did show some external germ in the last assessment, in both Chlorine IPC and MH, ‘says Esselink. ‘If we look at moisture loss, MH scores on average slightly better than Chlorine IPC.’
MH is particularly strong in combating internal germs in a sensitive variety such as Innovator, is Esselink’s experience. With Chlorine IPC, the share of internal germ in this variety in the storage study was almost 11 percent. No internal germ was found in the samples from MH-treated potatoes.
According to Esselink, the storage research of WUR Open Crops confirms the potential of MDs as a dormancy extender. ‘Certainly in combination with permitted space treatments, MH forms a solid basis for keeping ware potatoes quiet for a long time,’ he says.
‘However, in this study we have to point out that the 2017-2018 season was ideal for MH treatment. At the time, the agent was usually sprayed on a vital potato crop, and that is very important for good absorption and therefore proper functioning. ‘
UPL arable farming specialist Leen Struik states that despite the research results, it is not the intention to only recommend MDs for long-term storage. ‘Until February, MH often works sufficiently. If the potatoes sit longer, additional space treatments are often necessary, despite the longitudinal effect of MH. It remains important to regularly check batches. As soon as white dots are visible on the tubers, action is needed. ‘
Products such as 1,4Sight, Biox M or the Restrain system with ethylene are available for room treatments. In addition, UPL expects approval for a new sprout inhibitor in the not too distant future. This concerns a product based on a natural oil that is also evaporated in storage rooms.
The agents that may still be used after next year for administration in storage cells are considerably more expensive than Chlorine IPC, according to Struik. ‘The advantage of spraying MH is that lower dosages and fewer applications of the sprout inhibitors provide sufficient effect. Potato growers who keep for a long time can thus save about 25 to 30 percent on their costs for sprouting inhibition. ‘
Struik says that the use of MD in potatoes has increased sharply in recent years. According to him, many growers opt for this method of sprouting inhibition because of the reasonable control of potato storage and the side effect on continued crop. ‘The principle of three birds with one stone is appealing in practice.’Spraying on a vital crop has the best effectA recurring point of discussion about MDs is the best time to administer in the field. Leen Struik explains that UPL recommends spraying on a vital crop three to five weeks before the haulm killing. The arable farming specialist explains that, as an extra check, the tuber size under the crop is also looked at. ‘With 80 percent of the tubers larger than 25 to 30 millimeters, spraying would not be at the expense of the kilos.’ But according to Struik, in practice the yield loss due to MH also turns out to be better than expected in early applications. He points out that many plots were sprayed relatively early in 2018 because of the continued growth. ‘As far as is known, there was no negative effect on the final production. This is a confirmation of results in old English research.