Re: CULT: help - aphid predators?


From: John Montgomery <monashee@junction.net>

On Mon, 20 Dec 1999, you wrote:
> From: Gmbeasle@aol.com
> 

> Aren't aphids brought  by ants?  I always thought they were mostly unsightly 
> and a problem because of the ants tracking in diseases.
>   
The adult aphids are winged and fly from garden to garden to lay eggs.  I may
be wrong in this but I do not think ants actually move aphids around.  Some
aphid colonies may be "farmed" or tended by ants.  The ants are interested
because of the sweet sticky fluid produced by the aphids.

In general, these ants are doing no harm and may even be performing a service
to the extent that they clean up the syrup from the aphids.  Aphids in
themselves are not much of a threat to plants.  It would require a large
sustained attack before most healthy plants would suffer.

It is the aphids, not the ants which spread disease.  Many if not all aphids
will carry viruses and transmit them to each new plant they suck on.  Most
irises seem to have a fairly high resistance to viruses unlike some oother
genera where aphids can present a very serious threat.

When aphids are alarmed, it requies several seconds tor them to pull their
feeding tube from the plant.  If the tube gets broken off, the aphid will die.
Because of this, a hard spray of plain water from a hose is as good a control
method as any other.  Don't sort of spray over the top of the garden.  That
will set off alarms and they will retract their siphon tube.  Short, well aimed
hard blasts wil get them.  They may even climb back on the plant but they will
not be able to feed.

The usual advice for spraying aphids is to use a systemic insecticide. 
Unfortunately, if your motive for spraying is to stop the spread of virus, this
method is virtually useless.  The systemic insecticide only kills the aphid
after it has penetrated the plant and sucked in the poisoned sap.  During this
time it will have created a virus infection, if it was carrying viruses.

There are no cures for viruses but in almost all instances they do little long
term harm.  Humans do not die as a rule when they catch a virus.  Neither do
most plants.  The best treatment for virus in plants is to do nothing.  If the
plant dies you can be sure that was a fitting end for it no matter whether it
cost two dollars or two hundred.

Happy Christmas everyone

John Montgomery
Vernon  BC  Zone 5  Where it will be a white Christmas but I will be down in
the soggy rain forest.

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