Was the harlequin really bad news ?

[thunder]

Originally Posted by fairplay

So when they finally did arrive in the UK, why did some put out these scare stories of the Harlequin eating all the aphids, cannibalising our own native ladybirds, and worse. It makes you wonder.

Neil.

If someone had put out a press release that said "A new ladybird has arrived in the UK and we'd like to know where it has been seen" how many papers would have picked up the story and how many people would have bothered to look?

And as has been said, it is too early to know the final impact that Harlequins will make. Think of all the other introduced species that lurked around for years before making a major impression.

henrya

[Klaas Reißmann]

Hi,

I don't think that the impact of Harmonia axyridis will bring real harm to the native species. I would agree that there still might be a problem if the variability in size of the population is only because of cold and snowy or warm and wet winters. But analysis in Germany show a real big treatment of parasites, most of all by Nematoda. They will still be there in great numbers, because of their very high increase and their very big flexibility in feeding everything that lives.

I could watch them for three years on a tree in my garden getting fed almost by caterpillars of Geometridae and less by aphids. And they even fed on larvae and pupae of their own species and reduce themselfs. All this make them highly invasive, so Harmonia axyridis got spread all over Germany within three or four years.

Because of their very high increase they will bring populations of other insects down in the first two or three years, but for example I noticed at Henosepilachna argus I can find on a Bryonia dioica very close to my house, that it was nearly extinct on this plant in the first two years of H. axyridis, but today it is still there and in even bigger numbers than before. And I don't find any more H. axyridis on this plant.

I guess "nature will find it's way" with Harmonia axyridis. It will be a species we can't get out of our nature and it will always be there in big numbers. But you won't find the big numbers of the first years anymore and it will be part of our nature without making any problems.

@ fairplay

Harmonia axyridis was, as far as I'm informed, not introduced into Germany because of pestcontrol. It was introduced in the glashouses of Belgium or the Netherlands and escaped from there.

The fear of doing harm to our native nature was the same in Germany and the thought of doing harm is not out of our heads yet. I guess it is always the same warning, because you never know what problems it can bring. There are some more examples being called a pest and a problem for our nature, but till today they aren't. On the other hand Jason is absolutely right, that other introductions are a problem. So far one can't say someone's wrong or right.

Regards
Klaas

P.S.: I'd like to inform, that Harmonia axyridis is fed on every invertebrate that it is able to overwhelm and even bigger ones. So there are many records in Germany of Harmonia axyridis biting persons to lick blood.

[Paul mabbott]

As I've said here and elsewhere many times, I don't think we can draw any serious conclusions until we have ten years' data, preferably more. The dispersal and establishment of Harmonia axyridis hasn't finished (probably) and we certainly don't have an equilibrium. We may have sufficient data to conclude that the stablishment of H. axyridis coincides with the decline or even extinction of some other ladybird species but we have no data on the effects on other competitors (syrphids, spiders, Neuroptera &c) or on many prey species.

We can't take the continental experience as a guide - invasion of small islands is notoriously different from what occurs on continental land masses. Being and island and one on a climatic adge, it's quite possible that H. axyridis will never fully establish: it may appear in numbers in the NW one year and disappear the next.

The data suggests, however, that the species is well established in SE England and may be having an effect on numbers of other species. Numbers of Adalia bipunctata have declined massively over the past few years and, perhaps, so has Exochomus quadripustulatus. On the other hand, this last year was a 'good' year for Coccinella septempunctata in the SE, including the metropolitan area. Maybe (just speculation) H. axyridis & C. septempunctata have reached a stablemate by avoidance. Both species are very vagile - when large local densities build up they will fly away to 'new pastures' (or aphid sources!) - this could mean that they avoid competition and predation on local scales.

What is happening to the less common or more specialised species may be different. The editors of 'Ladybirds .... of Britain and Ireland' suggest that several species are in decline nationally - it will be good if naturalists follow this up over several years to see what is happening to these species.

[Paul mabbott]

Originally Posted by fairplay

.........
I think then, we can safely assume the expert/s in the UK got it wrong.
What I find surprising is when it was introduced into Germany and other countries to control pests, surely, especially Germany, would have done very thorough controlled tests before releasing the Harlequin and by the time it had reached the Nederlands, our own experts must have known there were no serious detrimental effects.
So when they finally did arrive in the UK, why did some put out these scare stories of the Harlequin eating all the aphids, cannibalising our own native ladybirds, and worse. It makes you wonder. Neil.

You can assume no such things!

The beast was introduced commercially into France, Holland and Belgium despite all advice to the contrary from ecologists. It was clear from the North American experience what would happen and the potential for destabilisation of native ecosystems was ignored. However, the agricultural/horticultural industries were sold on the idea with the result that we can see.
The 'stories' by and large are true - find a street tree in London with H. axyridis eggs on it, then go back a month later and you'll find that there are few other invertebrates than H. axy. As I've said below, we need more time to draw any conclusions - hopefully you'll help by contributing observations!

[Klaas Reißmann]

Sorry, Paul, we've got the time of almost 10 years here in Germany and no entomological section tells anything about any species getting rare because of H. axyridis. You had this effect for a short time of two or three years and after this everything went the well known way as before H. axyridis.

You can be right that ten years is almost nothing, but after thre years we got deviation as we know it of other species. We didn't get the huge bulk of specimen as we got in the first three years and since around six years we know that Harmonia axyridis is on the bill of fare of Nematodes and some parasitoids of Hymenoptera.

Experts have not been wrong. They had a theorie that did not come true yet. There is some damage for the first few years, but nothing that brings a species to extinction, not even to smaller populations than before. The specimen imported from the continent to Britain also brought there Nematodes with it and you surely will notice the same progress as you could notice in Germany: fast expansion, growing to huge numbers within very short time and than having kind of collapse and going down to smaller numbers. The beetle is very common around here and will be in future. But there is nothing giving me the believier that it could get worst.

Regards
Klaas

[Wild-Woman]

Some very interesting views and ideas brought up by all parties that have contributed to this thread. Lots of 'food for thought'.

Living as I do in the SE- Kent to be more accurate, I'm under the opinion (and this is only my view) that the initial wave of the Harlequins was quite over-whelming and we found them everywhere. However, with the past 2 winters being shockingly cold for us in the SE (yes we're quite soft down south I know), I feel that these beetles haven't done as well as the scientists thought that they may have.
During the summer on my 2 reserves that I work on, I found far more Seven spots and some of the rarer ones like the Water Ladybird in healthy amounts. The Harlequins, although present didn't appear in the numbers that they had previously.

It will be interesting to see what happens over the next decade or so. Will they cause irreversible damage, will they live in harmony- who knows. I wait with baited breath.

[Klaas Reißmann]

I should not forget to tell, that most of the Harlequins I found, were found in trees and bushes. So all the ladybirds in reed, in grassgrounds and others are with no harm of the Harlequins or just a little of the few, that can be found there. Maybe this could be one more interresting information, too.

Regards
Klaas

[Brian and Sophie]

for possible interest:
List of biocontrol agents (see annex III)

EPPO Panel on Safe Use of Biological Control