On Fri, 23 May 2003 08:41:21 +0100, Oz
wrote:

Robert Seago writes

On strawberries:

And I manage to grow them without a hint of pesticides.

I believe you, I doubt you are growing a 25ac field of them though.

The dynamics of pest infestation are quite interesting.

Typically, when a plant emerges, there are few pathogens about.

Then a race develops.
A few residual pathogenic spores (or insects) must find a susceptible
plant before they expire (the spore/insect that is), and mount a
successful attack on the plant.

From observations at the field scale before effective pesticides were
available the 'typical' success rate for these initial foci varied from
under 1 to 10/Ha.

So if you have a field in the 2-10 Ha range you are guaranteed to get
infected. If you are a gardener with 10 sqm (1/1000th Ha) then you would
be very unlucky to get hit.

Typically the foci spread pretty rapidly, depending on the number of
'offspring' and the generation time. So in a few weeks one pest has
become thousands (or millions) and the foci are a metre or two across
(which is when you notice them).

At this point the general infection level jumps up a gear if the pest
can spread by air. Generally insects spread much more slowly than fungi.

Even so, your garden plot may well miss the next infection cycle. This
is particularly true for insects, because most can home in on the smell
of host plants. They are MUCH more attracted to 25ac of crop than 10 sqm
of garden plot (which they may well not even detect). For fungi, you are
now getting quite likely to be attacked.

The next infection cycle pretty well trashes the field if not
controlled. The crop is a write off, and you just made a big loss.

Your garden is probably still OK, and although eventually probably gets
attacked, by then the season is over, or nearly so.

Never confuse the rate of pest attack between field scale and garden
scale.

How tall the tales.
--








So, you dont like reasoned,
well thought out, civil debate?

I understand.

/´¯/)
/¯../
/..../
/´¯/'...'/´¯¯`·¸
/'/.../..../......./¨¯\
('(...´...´.... ¯~/'...')
\.................'...../
''...\.......... _.·´
\..............(
\.............\..