Re: NZ flora

At 9:12 AM 3/16/99, Tony & Moira Ryan wrote:

>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

Dr. Raabe, in our conversation, said he'd recently talked with the leading
pomologist at UC who told him that--contrary to accepted wisdom--pears are
parthenocarpic, i.e. need no 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.

This was exactly the info in the aussie article.


 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.

Might be coincidental here.  Erwinia spreads only through blossoms.  Most
studies I've read lately show very mixed results with copper, though the
good doctor says that's because it must be applied to the blossoms to be
effective and many of the studies aren't careful about the timing.


 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.

In Cal it's much different with rapid spread from blossoms to stems in
Spring sometimes several feet down the stem in one season.  This is most
true in pears but apples, crabs, loquats, and other roseaceous stock do
sometimes suffer similarly.

>
>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.

I'm going to reread the article and see if I pick up any additional info
that I missed the first time through.  Thanks much for the feedback.  The
only trouble here is that my conversations with Dr. Raabe and with the
family Ryan opens up so many possible avenues of further investigation that
I could spend weeks tracking down the lot--which, if I do, will open up
even more mysteries, etc., etc., etc.

Jerry Heverly, Oakland, CA
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