Re: NZ flora

Jerry Heverly wrote:
> 
> Odd, sometimes, the serendipity of a group list this.  I had a meeting with
> Dr. Raabe,  the leading Emeritus prof of plant pathology at UC Berkeley
> Friday am.  Among other things we were discussing the bacterial disease,
> fireblight (*Erwinia amylovora*).  (snip)

> The aussie article had discussed a theory that the E.a. was crowded out of
> the flower petals(where it grows) by another bacteria, E.herbivore.  Baah,
> says Dr. Raabe, they probably just don't have very many bees in NZ.  I was
> skeptical;  it couldn't be that simple(thinks I).

 Jerry 
What ever the reason for the lower impact of Fireblight in NZ than
California it is not lack of bees, as Tony has already indicated. In
fact we also have vast numbers of imported hiving bunblebees as well
(they were brought in originally to pollinate red clover, but visit
enthusiastically almost every flower in my garden). Anyway, If you think
about it pome fruits MUST have some sort of pollinator, be it bees or
something else, and whatever does the job could  surely just as easily
distribute the infection. So I think your doubts of the good prof's
contention were well justified.

What we do notice here is that the disease when it occurs, seems to be
pretty low impact. Though I grow  a wide selection of apple and pear
trees in my garden I have only had it in my garden maybe four or five
times in over forty years, twice on pears and the other times on apples.
My impression is that it is relatively lacking in energy here and does
not spread quickly even on the pears. The two pear infections were
easily controlled by cutting off the infected shoot with a few inches of
clean stem and then spraying with copper. I don't know if it is the case
elsewhere, but the apple infections seem to be pretty well confined to
single clusters which do die but the infection does not then spread into
the stem.

I was very interested in the contention of the Aussie article about E
herbivore, as this could perhaps explain some of the reason why the
disease is of minor importance here also. The other possibility is that
perhaps we just have a not very vigorous strain.

Moira
-- 
Tony & Moira Ryan <theryans@xtra.co.nz>
Wainuiomata, 
New Zealand (astride the "Ring of Fire" in the SW Pacific).
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