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Freezing as a method of pest control for collections has been mentioned in one or two previous threads, and I have decided to try it myself. Has anyone experience of this method and if so, any helpful tips? For instance, do store boxes need to be opened during freezing, or does the method work with closed boxes?

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It will work with closed boxes, and indeed, I would not try it with open boxes for fear of ice getting in and wetting the collection once out of the freezer and thawed.

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I agree with Susan. in fact it's not a bad idea to seal the storebox in a polythene bag before freezing as well. The recommended temperature is -30 for two days, but if your freezer does less than this, freeze once, then allow to come to room temperature for a couple of weeks then freeze again. The theory is that eggs which may survive the initial freezing will hatch and the young larvae will be killed by the second freeze. However there is some debate about whether this actually the case. Ideally freeze to something near -30 if you can. Chest freezers usually approach this - upright frezers are not usually so good. Ice boxes (as found in old fridges) are no good at all - most insects can survive the few degrees of frost they generate.

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Thanks for that. I have a chest freezer so it looks as though that will be suitable. My wife doesn't object to the frozen water shrew and tawny owl in there (much) so I'm sure a box of flies will be ok.

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Temperature -30 in???C Degree?

Attention, the eggs of Dermestidae of the same laying can hatch over one year!

Then the boxes must tight if not be again attacked!

It is a healthy process!

To make this treatment into preventive before putting in collection!

Attention, the insects must be quite dry if not they are split and the labels and the ink of the labels must resist water!!!!!!

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In the Natural History museum of Tilburg, we use -30C for a week period. That should be enough, combined with good closing boxes. If you do it regularly (eg once a year), there should be no problem.
(personally, I just use good boxes, never had a problem).
Sealing the boxes with plythene before freezing never occurs here.

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I freeze store boxes occasionally in my chest freezer. I usually wrap them in a thin polythene bin-liner bag and leave them at about -20C for a few weeks. Afterwards just bring the box into the house and allow it to come to room temperature before unwrapping it and opening it. :)

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Thanks to everyone for their helpful advice!