Release of Psyllid Aphids
March 9th, 2010 by Mike Clough
I have been prattling on about the Psyllid aphid release that has been suggested by CABI (a Government funded ‘not for profit’ organisation) and I will admit I have been very negative.
In my defence I would point out that my initial reaction on hearing of the
suggested bio control of Japanese Knotweed – was to contact CABI and in
particular Dr Richard Shaw in an effort to get myself up to speed on what was being suggested. Unfortunately I didn’t get a response to either phone calls or emails.
Instead of keeping quiet and awaiting release of information I put my thoughts in writing - which ended up on my Blog - which ended up being circulated around the internet ….and most of what I said was wrong.
I attended a recent seminar in Sheffield where Dr Shaw explained the reasoning behind the aphid release and the science behind the decisions that have been made….and it all made reasonable sense!!
Dr Shaw explained that the Psyllids (pronounced syllids) are very specific about what they will eat – and if they can’t find their specific food source they will die. SO in theory at least they shouldn’t go round eating any of our native plants. He went on to explain that the Psyllid won’t defoliate the plant (an assumption that I had made) IN FACT - the foliage will actually be more abundant in season two – making the application of chemical control MORE effective…also the plant will be weaker due to the psyllid predation - and thus should be easier to kill…
CABI are assuming that there will be a cycle of peaks and hollows in the
abundance of aphids – one season lots of aphids and a reduction in JK cover – next season less JK therefore less for the aphid to eat therefore it dies back – season three more JK because there are fewer aphids – season four more aphids due to mass of JK growth etc etc in a cyclical pattern (a little like Ragwort and the Cinnabar Moth to those of you familiar with that cycle).
Dr Shaw pointed out that he did not expect that the Aphid would be the one stop answer to all of our Japanese Knotweed problems. CABI also do not expect the Psyllid to kill the Knotweed plant on which it lives. What they are expecting is that a balance will be achieved between the predator and host which will reduce the invasive nature of the Japanese Knotweed and prevent the continued unchecked spread of the plant.
This must be supported by anybody either in the industry or anybody
wishing to see our native countryside protected.
I do still have some concerns about the use of one pest to get rid of another and the fact that the Psyllid has no natural enemies in the UK – however I now feel more inclined to accept the fact that this release is going to happen.
Our approach at Japanese Knotweed Solutions will be to work with the
Government experts - and try to ensure that we continue to offer our clients the most up to date practical advice on controlling and managing Non Native Species.
And in future I shall learn to keep my mouth shut until I am fully aware of all the issues.
Mike C
