Aphids in conifer

[Dinasaw]

Hi, all you Gardening People!
I have already posted this query in the insect forums, and had a couple of replies, but more answers would be a help. We have an infestation of very large black aphids in a conifer ( presumed an ex-Christmas tree, so maybe an abies or picea, possibly the former as it has lovely deep pink young cones on it this year - never seen them before - referring to a Tree Book ) The aphids were present last year and attracted lots of flies and wasps - but to date the 'colony' is much bigger, as are the insects themselves. about 5mm long and 3mm across. One day last week, they appeared to be swarming up the tree from an underground nest - really creepy-crawly, I'm afraid!!
I would like to know why they are here, and if the colony is going to continue to grow and cause problems to the rest of my garden?
They are not moving out very far yet - a few creeping around my shed, and don't have wings - do they metamorphose and fly off??
I put pictures with my insect posts, so will try again, but it took me 2 days to fathom out the technology!
Many thanks - and let's have some rain please!

[Cotham Marble]

Originally Posted by Dinasaw

I would like to know why they are here, and if the colony is going to continue to grow and cause problems to the rest of my garden?
They are not moving out very far yet - a few creeping around my shed, and don't have wings - do they metamorphose and fly off??

These are very likely a form of 'root aphid' of which there are many types although certain plants are favoured by some species - have a look at this report for three species found on Picea abies.

Whether the aphids will cause actual harm to your tree is not easy to predict, or whether other plants will be affected is also difficult to tell, my guess is that only other conifers would be affected. For more information about tree damage I'd suggest posting on the Trees sub forum where you might get the interest of WAB arborculturalists.

CM

[Paul mabbott]

Originally Posted by Cotham Marble

These are very likely a form of 'root aphid' of which there are many types although certain plants are favoured by some species - have a look at this report for three species found on Picea abies.

Whether the aphids will cause actual harm to your tree is not easy to predict, or whether other plants will be affected is also difficult to tell, my guess is that only other conifers would be affected. For more information about tree damage I'd suggest posting on the Trees sub forum where you might get the interest of WAB arborculturalists.

CM

Or the insects forum where someone may know about aphids!
These are probably adelgids. Possibly a species that overwinters underground possibly feeding from the roots. They move up to the foliage with warmer weather where they feed on the sap, reproduce and (some of them) disperse. They can cause damage to trees if they are in large enough numbers - other influences may include the weather and the variety of the tree (trees bred for garden aesthetics tend to be less robust than native varieties).

If you're really concerned about the fate of your tree, you might want to spray any dense colonies with water containing a few drops of washing-up liquid - will keep aphid population down and not do much harm to anything else!

[Dinasaw]

Thank you, both.
Yes I will try the washing-up liquid technique - I know it did the trick on 'ordinary' blackfly on the honeysuckle. But the conifer guys look so much bigger and stronger......
Thanks for the link to the report from Lancaster Uni!
So much info and knowledge on this site - all only a click away!

[Cotham Marble]

Originally Posted by Dinasaw

Yes I will try the washing-up liquid technique - I know it did the trick on 'ordinary' blackfly on the honeysuckle. But the conifer guys look so much bigger and stronger......

Do bear in mind that aphids are food for a whole range of other creature and that as long as the plant can support the aphids without it suffering obvious damage, then tolerating their presence is a plus for wildlife at no cost to you. The intolerance of aphids comes from 'classic' home gardening or commercial production where prize blooms and maximal crop production have been the defining purposes.

Not that I'm an especial fan of black aphids, and I have been known to evict them from a favoured plant - I find using a small stiffish paint brush to be more effective than washing up liquid, where possible brushing the aphids into a container for deposit on the bird table.

CM

[Dinasaw]

Thank you again - I haven't actually done any washing-up water squirting yet (been otherwise occupied with our daughter's wedding -Wooo-hoo!!) so I think I will just leave them. They don't seem to be damaging the tree itself, and are not bothering me at all, now that I have moved the dustbins from beneath the tree to another spot - and I have noticed some birdy activity around the tree. Perhaps the blackbirds will be distracted from pulling my newly-planted patio trough to bits!