Galanthus pests

[Anthony Darby]

The thing about these larvae is that one can do a lot of damage. They don't have to be common for that one rare caterpillar to be in your favourite clump, where it could munch the bunch in two years!

[Alan_b]

If I lift and divide my snowdrops I can be fairly confident that I will find these larvae.  So even if they are rare in the country as a whole they are common in my locale.  They may not be sufficiently common to have eliminated the snowdrops from my garden but they are making valiant attempts.  I'd even be prepared to do a certain amount of live-and-let-live with my more common/prolific snowdrops if I could find a way of excluding them from certain areas.  For example, perhaps a fleece covering at the time of year when the moths are laying their eggs would do the trick?  I used to keep my snowdrop that are in pots under a hedge in summer and that seemed to work but now I have too many to do that and the larvae are getting into the pots.   

[ronm]

The adults are on the wing in June usually Alan. The female will drop the eggs whilst in flight, so a covering of some type may well help. Say from beginning of May to end July to be safe.
It is obviously reached pest proportions with you, and I am at a loss really to understand why. Is your growing area totally surrounded by a high fence or hedge? The egg laying strategy of these moths is to widely broadcast eggs rather than lay in clumps. Perhaps you had a single gravid female that was unable to fly and laid all ( hundreds ) of her eggs in your garden. Have you had this problem for many years? I'm afraid the only control method is 'hand picking'. But if they are trapped there then they will only return in future, as you'll never get every last larvae.
Interestingly I can find no documented evidence, so far, of this being a recognised pest of Galanthus. Narcissus fly, yes, everywhere. But this moth no. Maybe because 'drops aren't grown on a massive scale?
No need to live and let live with your common 'drops though Alan. If there is a local patch of rough ground, pop them on there. They eat much anything, but grass roots have always been thought to be the primary foodstuff. Even when present on  grass their is no damage noticeable.

[Alan_b]

Hmm, Galanthus leaves usually die back some time in May.  I would like a covering that lets enough light through that I don't unduly hasten this process, that lets water through but has a fine-enough weave that the small eggs of a swift moth would be trapped.  Any suggestions?  Presumably such a covering, if it exists, would also work against narcissus flies. 

[ronm]

Would a standard horticultural fleece not suffice? It works perfectly against narcissus flies, so long as they can't get under the edges.

[Alan_b]

Quite possibly horticultural fleece would do fine; it's just that I don't normally use fleece so have no experience of what it can and cannot do.  Is there more than one thickness/density or is it entirely standard?   

[ronm]

I'm unsure about various grades etc. Alan. We use the regular stuff from the garden centre to keep the insects off our vegetables, so I'm sure it would work for you. Just ensure the edges are tight to the ground. Probably best to cover the edges with a little soil or sand to ensure no gaps.
It will have to be a war of attrition though Alan I'm afraid . If you have as many as you think then you must have one year old and two year old larvae present, so you may have to take the long view. If you do cover your 'drops then you will find the adult moths trapped underneath around June time. I'd check daily if possible, early morning being best. Hopefully by taking the adults you can gradually reduce the population. They are also very much attracted to light ( especially the females ). It may be worth keeping an eye on house windows etc. during the flight time.
Also the egg laying period of the narcissus fly is early May to June so by covering you may help avoid this problem as well.

[Alan_b]

I was talking to a vegetable-growing colleague over lunch.  He reckoned the main problem with using horticultural fleece was that things can over-heat underneath it.

Do you think the moths could still meet, mate and lay eggs in the confined space under a fleece?

[ronm]

I'm pretty sure they could Alan.