In message , Franz Heymann
writes

"Kay Easton" wrote in message
...
In article , Mushtywoof
writes
SCREAM

I went into my greenhouse today and spotted mealy bug on a handful of
cacti.........how can i get rid of them ?

Simplest way on a nice warm sunny day with a fine brush dipped in meths
and pick the white fluff off and any adults. Keep doing it for a few
weeks.

I have a can of spray stuff
(cant
recall the name offhand) but it says to 'water well prior to spraying'.
As
the cacti are now to be kept dry till spring what can i do ?

Be a little bit careful with unknown random pesticides indoors. Cacti
have thick waxy coats and some formulations will damage them which at
this time of year means they will dessicate during the winter rest.

I like to be 'organic' so dont routinely spray to debug 'just in
case'.....is this my downfall ?

No .. they seem to develop resistance to pesticides quite easily. You'd
have got to the same state even with regular spraying ;-)

Kay, could you do a bit of explaining please:

I presume that the development of a resistance to a pesticide is a genetic
process. I envisage it as occcuring when one specimen undergoes a genetic
modification in the desired direction, and subsequent sexually transmitted
mixings spreading it through a population. If this is so, I don't think one
will notice as quick an immunity as you imply.

Please tell me what I misunderstand.

Mainly that the mealy bug tend to have come in with plants from
commercial nurseries where they have already become immune to most of
the commonly used insecticides. You often see buy and die plants in some
garden centres literally humming with mealy bug on warm days.



Regards,
--
Martin Brown

In message , Franz Heymann
writes

"Kay Easton" wrote in message
...

I'm talking about a time scale of years rather than months.

Nuff said.

A greenhouse
is a largely closed environment, so it's more of a problem than the
garden generally. Certainly I no longer find pesticides effective
against mealy bug and red spider mite.

It is also true that the mealy bug in some commercial greenhouses have
already become immune to several of the pesticides available to
amateurs. It is not uncommon to see "buy and die" plants in certain
garden centres literally humming with mealy bug in the sunshine.

This means when you buy new plants they need to be quarantined until you
can hit them with something suitably deadly to make sure nothing nasty
is lurking. Root mealy bug is much more of a nuisance in cacti.

Ordinary mealy tend to go for the growing point and are relatively easy
to hit with a brush dipped in meths.

Generations in both mealy bug and rsm come thick and fast!

I understand better now, thanks. I had an impression (wrongly) that you
meant that the effect might be seen within a season.

You can delay the onset of trouble by alternating between a systemic and
a couple of different contact knock down insecticides. I use dimethoate,
malathion and synthetic pyrethrums on mine and don't have that much
trouble. Only the last one is acceptable for house plants.

ISTR one brand of phostrogen plant pins did fairly well in a BCSS test.
(But that isn't much use to you outside the growing season)

NB Some cacti and succulents will react badly to the solvents and
wetting agents in certain commercial formulations of insecticide.
Especially true going into winter since damaging the waxy coat means
more water loss.

Regards,
--
Martin Brown

"Martin Brown" wrote in message
...
In message , Franz Heymann
writes

"Kay Easton" wrote in message
...

I'm talking about a time scale of years rather than months.

Nuff said.

A greenhouse
is a largely closed environment, so it's more of a problem than the
garden generally. Certainly I no longer find pesticides effective
against mealy bug and red spider mite.

It is also true that the mealy bug in some commercial greenhouses have
already become immune to several of the pesticides available to
amateurs. It is not uncommon to see "buy and die" plants in certain
garden centres literally humming with mealy bug in the sunshine.

This means when you buy new plants they need to be quarantined until you
can hit them with something suitably deadly to make sure nothing nasty
is lurking. Root mealy bug is much more of a nuisance in cacti.

Ordinary mealy tend to go for the growing point and are relatively easy
to hit with a brush dipped in meths.

Generations in both mealy bug and rsm come thick and fast!

I understand better now, thanks. I had an impression (wrongly) that you
meant that the effect might be seen within a season.

You can delay the onset of trouble by alternating between a systemic and
a couple of different contact knock down insecticides. I use dimethoate,
malathion and synthetic pyrethrums on mine and don't have that much
trouble. Only the last one is acceptable for house plants.

ISTR one brand of phostrogen plant pins did fairly well in a BCSS test.
(But that isn't much use to you outside the growing season)

NB Some cacti and succulents will react badly to the solvents and
wetting agents in certain commercial formulations of insecticide.
Especially true going into winter since damaging the waxy coat means
more water loss.

Now you have made me worried about your suggestion of using meths. Might
not the alcohol dissolve some of the wax?

Franz

"Martin Brown" wrote in message
...
In message , Franz Heymann
writes

"Kay Easton" wrote in message
...
In article , Mushtywoof
writes
SCREAM

I went into my greenhouse today and spotted mealy bug on a handful of
cacti.........how can i get rid of them ?

Simplest way on a nice warm sunny day with a fine brush dipped in meths
and pick the white fluff off and any adults. Keep doing it for a few
weeks.

I have a can of spray stuff
(cant
recall the name offhand) but it says to 'water well prior to
spraying'.
As
the cacti are now to be kept dry till spring what can i do ?

Be a little bit careful with unknown random pesticides indoors. Cacti
have thick waxy coats and some formulations will damage them which at
this time of year means they will dessicate during the winter rest.

I like to be 'organic' so dont routinely spray to debug 'just in
case'.....is this my downfall ?

No .. they seem to develop resistance to pesticides quite easily. You'd
have got to the same state even with regular spraying ;-)

Kay, could you do a bit of explaining please:

I presume that the development of a resistance to a pesticide is a
genetic
process. I envisage it as occcuring when one specimen undergoes a
genetic
modification in the desired direction, and subsequent sexually
transmitted
mixings spreading it through a population. If this is so, I don't think
one
will notice as quick an immunity as you imply.

Please tell me what I misunderstand.

Mainly that the mealy bug tend to have come in with plants from
commercial nurseries where they have already become immune to most of
the commonly used insecticides. You often see buy and die plants in some
garden centres literally humming with mealy bug on warm days.

That sounds like an extremely dubious commercial practice.

Franz

In article , Martin Brown
writes

You can delay the onset of trouble by alternating between a systemic and a
couple of different contact knock down insecticides. I use dimethoate,
malathion
and synthetic pyrethrums on mine and don't have that much trouble. Only the
last
one is acceptable for house plants.

I used to alternate between dimethoate and malathion, and now have
resistance to both.

I've gone over to the predator with rsm, which is working well, and
toothpick for mealy bug.
--
Kay Easton

Edward's earthworm page:
http://www.scarboro.demon.co.uk/edward/index.htm

In article , Bevan Price
writes


If the cacti are sufficiently robust, I would risk getting them wet, and try
to physically remove as many as possible of the mealy bugs by holding the
affected areas under a fast runnning cold water tap, or blast the affected
areas with a water jet from a garden spayer. Wear gloves and hold the pot
and plant approximately horizontal during spraying to minimise the amount of
water landing on the soil / compost in the pot. This may remove most of the
mealy bugs, leaving just a few to remove by hand.

It doesn't! I've tried that one! And it certainly doesn't remove the
eggs.
Standing the entire cactus upside down in warm soapy water overnight
seems to kill but not remove the mealy bug, but I wouldn't recommend
this on any plant which you love ;-)


--
Kay Easton

Edward's earthworm page:
http://www.scarboro.demon.co.uk/edward/index.htm

In message , Franz Heymann
writes

"Martin Brown" wrote in message
...

NB Some cacti and succulents will react badly to the solvents and
wetting agents in certain commercial formulations of insecticide.
Especially true going into winter since damaging the waxy coat means
more water loss.

Now you have made me worried about your suggestion of using meths. Might
not the alcohol dissolve some of the wax?

Meths and for that matter IPA seem not to cause too much damage. The wax
might go misty though leaving a mark. The object is to pick the mealy
off with a fine brush dipped in alcohol rather than soaking the plant.
Since they sit near the tender soft growing tip that is more vulnerable
than mature plant skin. Some of the solvents used in commercial
insecticides are distinctly phytotoxic to cacti (and other plants with
special waxy coats).

It is always as well to test insecticides on less important plants
before using them on large, valuable or rare ones.

Regards,
--
Martin Brown

In message , Kay Easton
writes
In article , Martin Brown
writes

You can delay the onset of trouble by alternating between a systemic and a
couple of different contact knock down insecticides. I use dimethoate,
malathion
and synthetic pyrethrums on mine and don't have that much trouble. Only the
last
one is acceptable for house plants.

I used to alternate between dimethoate and malathion, and now have
resistance to both.

Bad luck. They are too closely related organophosphorus compounds. You
need to use at least one completely unrelated pesticide to avoid build
up of resistance. And I prefer to cycle between 3 different ones.

Dimethoate is still my pesticide of last resort. And so far it has
worked.

I've gone over to the predator with rsm, which is working well, and
toothpick for mealy bug.

I have only ever had much bother with root mealy. The others were fairly
easily controlled by occasional spraying and a ruthless quarantine
policy of new plants.

Regards,
--
Martin Brown

On Mon, 3 Nov 2003 09:48:23 +0000 (UTC), "Franz Heymann"
wrote:


Mainly that the mealy bug tend to have come in with plants from
commercial nurseries where they have already become immune to most of
the commonly used insecticides. You often see buy and die plants in =
some
garden centres literally humming with mealy bug on warm days.

That sounds like an extremely dubious commercial practice.

It's certainly true in the Netherlands.

--=20
Martin

martin wrote:
On Mon, 3 Nov 2003 09:48:23 +0000 (UTC), "Franz Heymann"
wrote:


Mainly that the mealy bug tend to have come in with plants from
commercial nurseries where they have already become immune to most
of the commonly used insecticides. You often see buy and die
plants
in some garden centres literally humming with mealy bug on warm
days.

That sounds like an extremely dubious commercial practice.

It's certainly true in the Netherlands.

...... But we hold the Netherlands in such high horticultural esteem.
.............Well, all bar that Bakker mail order outfit, that is.
'Won't ever deal with them again.

--
ned

On Tue, 4 Nov 2003 23:36:57 -0000, "ned" wrote:

martin wrote:
On Mon, 3 Nov 2003 09:48:23 +0000 (UTC), "Franz Heymann"
wrote:


Mainly that the mealy bug tend to have come in with plants from
commercial nurseries where they have already become immune to most
of the commonly used insecticides. You often see buy and die
plants
in some garden centres literally humming with mealy bug on warm
days.

That sounds like an extremely dubious commercial practice.

It's certainly true in the Netherlands.

..... But we hold the Netherlands in such high horticultural esteem.
............Well, all bar that Bakker mail order outfit, that is.
'Won't ever deal with them again.

What did they do to you? They are one of the biggest in NL.
They used to employ lots of British casual labour in their mail order
department.
Years ago we bought 57 beech hedge plants from their garden centre, 3
actually grew. We think that they were probably already DOA at Bakker.

We had no problems with other plants that we bought from Bakker.
--=20
Martin

martin wrote:
On Tue, 4 Nov 2003 23:36:57 -0000, "ned" wrote:

martin wrote:
On Mon, 3 Nov 2003 09:48:23 +0000 (UTC), "Franz Heymann"
wrote:

snip
You often see buy and die
plants in some garden centres literally humming with mealy bug
on
warm days.

That sounds like an extremely dubious commercial practice.

It's certainly true in the Netherlands.

..... But we hold the Netherlands in such high horticultural
esteem.
............Well, all bar that Bakker mail order outfit, that is.
'Won't ever deal with them again.

What did they do to you? They are one of the biggest in NL.

We placed quite a big order for herbaceous plants and when they
arrived it looked like the sweepings from the packing bay floor. We
complained. We received a very condescending response advising us that
the plants were in a dormant state and that we should wait to see what
success we had when they revived. We pointed out that many were
actually black & rotting in their plastic containers and were never
likely to flourish, and asked how they intended to replace those that
did not survive four or five months after the autumn planting season
had passed. They sent replacements for those that were actually rotten
and those were hardly better than those we had complained of. We
eventually got a full cash refund. But never again.

'Disgusted' of Tunbridge Wells.

"ned" wrote
..... But we hold the Netherlands in such high horticultural esteem.
............Well, all bar that Bakker mail order outfit, that is.
'Won't ever deal with them again.
ned

I agree - total waste of time. Most of the plants arrive in a bad condition.

I once went to their nursery and the general state of that was the final straw !
Jenny

"JennyC" wrote in message ...
"ned" wrote
..... But we hold the Netherlands in such high horticultural esteem.
............Well, all bar that Bakker mail order outfit, that is.
'Won't ever deal with them again.
ned

I agree - total waste of time. Most of the plants arrive in a bad condition.

I once went to their nursery and the general state of that was the final straw !
Jenny

It wasn't me that burnt their garden centre to the ground, 'onest gov. ...

On Wed, 5 Nov 2003 08:37:33 +0100, "JennyC" wrote:


"ned" wrote
..... But we hold the Netherlands in such high horticultural esteem.
............Well, all bar that Bakker mail order outfit, that is.
'Won't ever deal with them again.
ned

I agree - total waste of time. Most of the plants arrive in a bad =
condition.

I once went to their nursery and the general state of that was the final=
straw !

Don't they buy most of there stuff wholesale from Boskoop?
--=20
Martin