Scottish Rock Garden Club Forum

General Subjects => General Forum => Topic started by: David Shaw on February 26, 2012, 09:52:58 AM

Title: Un-identified grubs
Post by: David Shaw on February 26, 2012, 09:52:58 AM
I have found these grubs in my home made potting compost and have not seen them before. The compost contains loam, leafmould and grit so I would think that the loam is the most likely source. The loam is made from lawn turf which was dug and stacked several years ago. I have been using the stack for years and not found the grubs before. They are very difficult to spot in the compost and these specimens have been washed off under the tap. They have a rather leathery skin but the grubs that I know as leatherjackets are mush fatter than these.  I have tried my own web searches but while I can find plenty of illustrations of invertebrates there are very few of the larvae.
Title: Re: Un-identified grubs
Post by: ranunculus on February 26, 2012, 10:21:03 AM
If you lived in the States, David you would be able to use this superb resource:-

http://www.ipm.iastate.edu/ipm/icm/indices/insectsandmites.html
Title: Re: Un-identified grubs
Post by: David Shaw on February 26, 2012, 10:25:18 AM
Useful site, Cliff, but not really worth moving for  ;)
Title: Re: Un-identified grubs
Post by: ranunculus on February 26, 2012, 10:29:52 AM
 ;D
Title: Re: Un-identified grubs
Post by: Anthony Darby on February 26, 2012, 07:12:24 PM
Fly or perhaps moth larvae. Not welcome in a potting compost. :-\
Title: Re: Un-identified grubs
Post by: David Shaw on February 26, 2012, 07:21:12 PM
Ah, Anthony, I was waiting for morning in NZ  ;D. Would you care to risk a closer id or suggest any other web sites that might help? I am surprised at the lack of response from the Forum experts, obviously no one knows, and have just forwarded the picture to Garden Organic and the Soil Association.
Title: Re: Un-identified grubs
Post by: daveyp1970 on February 26, 2012, 07:47:51 PM
Could they be some sort of saw fly larvae?
Title: Re: Un-identified grubs
Post by: Anthony Darby on February 26, 2012, 07:53:23 PM
They are the larva of the St. Mark's fly (Bibio marci). Interesting, as I was singing in the choir at St Mark's, Remuera yesterday (Sunday) morning. They are usually scavengers, but do eat plant roots. The grubs, not the members of the choir.
Title: Re: Un-identified grubs
Post by: Lesley Cox on February 26, 2012, 08:14:13 PM
Are these the same as some pictured in another thread a couple of months ago or round about then. I thought they were leather jackets but they weren't, they were some kind of fly which was mentioned by name. A search (?) might bring them to light.
Title: Re: Un-identified grubs
Post by: Maggi Young on February 26, 2012, 08:57:50 PM
Well done, Lesley... you may not have much success with the search... but you give me the clues and I then find it..... :D

Yup, same critters, I think.... http://www.srgc.org.uk/forum/index.php?topic=8164.0
Title: Re: Un-identified grubs
Post by: David Shaw on February 26, 2012, 09:29:57 PM
OK, thanks for doing the search, Maggi. I don't think that my grubs are the same as Rob's because Rob's seem to be on the surface in the light and mine seem to avoid the light. At the moment I much prefer Anthony's suggestion of St. Mark's/Hawthorn Fly larvae as we do have quite a colony of these black flies with the freaky long, dangling legs around the garden. Trouble is, on the web, I can only find pictures of the adults, none of the larvae. Also, I do not hear any choral music coming from my grubs!!!!!
Title: Re: Un-identified grubs
Post by: Anthony Darby on February 26, 2012, 09:44:01 PM
Here's a link: http://www.tuin-thijs.com/gnats-engels.htm
Title: Re: Un-identified grubs
Post by: Maggi Young on February 26, 2012, 10:08:03 PM
Anthony and Armin thought they were of the same species  then, David. Also it was said that they could be found on the surface at that time of year. Seems likely they would  not want to be exposed at this time of year.
Title: Re: Un-identified grubs
Post by: David Shaw on February 26, 2012, 10:51:42 PM
'K, I see where you are all coming from. I am prepared to go along with the Bibio sp. flies which may or may not be OK in the compost.  I spent an hour this afternoon 'cleaning' a gallon of said compost of these larvae. It seems that I have a lot more to do! Still, the small birds will be happy tomorrow.
Title: Re: Un-identified grubs
Post by: Maggi Young on February 26, 2012, 11:14:16 PM
Better safe than sorry, I think, David.... it seems the little devils will happily chomp on plant roots if Wikipedia is to be believed: " larvae are known to be root damage pests of celery, asparagus, roses, saxifrages, lawn grass, lettuce and Polyanthus. They also feed on a very large number of plant species that are commercially unimportant."
Title: Re: Un-identified grubs
Post by: Lesley Cox on February 27, 2012, 12:08:13 AM
The ones I killed with boiling water were like the hairless one taken on 9/4/11 and the pic above it, is roughly what I know as daddy-long-legs, so maybe I wasn't too far out. The one we have here in numbers maybe a different species, don't know, but very similar.
Title: Re: Un-identified grubs
Post by: David Shaw on February 27, 2012, 10:37:40 AM
The larvae of crane fly and St Mark's fly are very similar, Lesley, mainly it is the head that is different. To confirm the exact species of these Bibio larvae it seems that I would have to carry out an anal inspection; somehow I don't think so .... The good news is that Bibio just have a one year life cycle so, when these larvae pupate into flies in spring this infestation should be finished.
Title: Re: Un-identified grubs
Post by: Lesley Cox on February 27, 2012, 09:29:41 PM
But will the flies not lay eggs which will turn into larvae then into pupae.....?
Title: Re: Un-identified grubs
Post by: Anthony Darby on February 28, 2012, 06:40:18 AM
Perhaps David is expecting it to rain for forty days and forty nights, in which case only two will survive? ;D
Title: Re: Un-identified grubs
Post by: David Shaw on February 28, 2012, 07:56:22 AM
That's next years problem, Lesley :-[ We have had the flies around for years and this is the first time i have found the grubs in the loam. Hopefully they will lay somewhere else this year.
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