onion fly?

MarkG · « **on:** July 08, 2008, 20:39 »

Hi All,

The tops of some of my onions were bending over, so I loosened and pulled them. Some were soft round the root and peeling away a couple of layers revealed small brown casters (or they look like casters used in fishing). Could these be onion fly casters? They are about 1/2mm in diameter and maybe 2 or 3mm long.

I've read some posts that say the whole crop is likely to be infected so should be pulled and chucked. In practice is this likely, or is it OK to inspect each onion when its pulled and just throw the ones that show signs of the fly/maggot.

Any advice on what, if anything, can be done would be appreciated.

Thanks.

gobs · « **Reply #1 on:** July 08, 2008, 22:15 »

Onion fly is quite a bit longer than that, so hopefully not.

I had to check caster in the dictionary to decide it was a typo.

Did not make me wiser, do you mean tunnels?

Bignij · « **Reply #2 on:** July 08, 2008, 22:16 »

Casters are maggot pupae!

MarkG · « **Reply #3 on:** July 08, 2008, 22:27 »

Yes, sorry, meant pupae.

I found a website here http://www.nysipm.cornell.edu/factsheets/vegetables/onion/om.pdf

which shows a picture of what I found. The picture labelled number 4. My current theory is that the presence of the maggots (before they became pupae) caused the stems to bend over. I wasn't expecting the onions to be ready until August time, and they nearly all have upright stems and look healthy.

So tomorrow I'll pull any remaining with bending stems, or any suspicious looking stems of any sort, and also pull a dozen or so healthy looking ones and check them for pupae or maggots.

Also a couple of sites I read said that the maggot crawls back into the soil before turning into a pupae. Mine have stayed in the onion.

gobs · « **Reply #4 on:** July 08, 2008, 23:35 »

Oh, thanks, learnt a new word there.

That's for over-wintering, Mark, there are several generations a year.

I'd personally be tempted to do what you pretty much suggest to the extreme and pull all of them up - I'm not using toxins in my gardens, so everything, I'm doubtful about comes out, as soon as poss -, and dry the good ones in some sunny , aery place.

You can be lucky too, as bean flies sometimes do pester onions too, very similar but don't do quite that much damage.

Just take them up and well turn the soil a few times till next season and use for other crops than onion types for a few years.

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