How does spider mite attack actually kill a plant?

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Posted by AL_n on August 11, 2011, 5:11 pm
 
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It took me many attemts to get a successfully rooting cutting from a
hibiscus shrub. Then when I finally succeeded, it got attacked by what I
guess was spider mites. I could see a load of minute dead white bus on the
undesides of the leaves and a few cobweb-like starnds too. The leaves all
sort of dried up, and the plant seems to have given up the ghost, despite
having grown decent roots. How does this happen? Can I revive the baby
shrub?

TIA

Al


Posted by Martin Brown on August 11, 2011, 5:27 pm
 On 11/08/2011 22:11, AL_n wrote:

Real red spider mite are very pale yellow and need a magnifying glass to
see them. You generally can only see the webs they spin and a bunch of
tiny dots moving about.

Red spider mite doesn't usually kill otherwise healthy plants. Spray or
use a systemic insecticide that is specific against red spider mite.
Provado seems to be still reasonably effective.

http://www.bayergarden.co.uk/products/product.aspx?productid 8&categoryid

Putting it outdoors might be enough for most things to recover. I have
only ever had serious bother with rsm under glass and only really
because it can scar the growing points of cacti and succulents.

Regards,
Martin Brown

Regards,
Martin Brown

Posted by Pam Moore on August 11, 2011, 5:38 pm
 

I just discovered red spider mites on my tender morning glory which I
had brought indoors because the wind was battering it.
Been away for a few days and noticed all the leaves looking mottled.
Tried to see them with a x10 magnifier but my eyes aren't good enough.
Got a friend to look and he saw the webbing as well, so it's outside
again and has been rained on and may get a spray of some sort.  They
are  devils, hard to get rid of, and it's a mystery where they come
from.  I've had no rsm for several years and have very few houseplants
these days.
They say that spraying with water helps as the rsm (not regimental
sergeant major!) thrive in dry conditions.

Pam in Bristol

Posted by Martin Brown on August 12, 2011, 5:07 am
 On 11/08/2011 22:38, Pam Moore wrote:

Spray or water with a systemic insecticide. Provado seems effective and
can be used either way (or both ways). Alternate with some other contact
insecticide you don't want to encourage them to gain immunity.

You have to make it very humid and steamy before rsm get discouraged.
I have never had a serious problem with rsm outside in the UK.

There is a predator mite for biological control though I have never had
any luck with it.

I do have some obscure mite that only target my snowdrops in spring, but
they just make the leaves go a bit silver. I asked for an ID once and
was told that it was only possible by electron microscopy of the mouth
parts. I leave them alone as the bulbs don't seem to suffer.

Regards,
Martin Brown

Posted by Rod on August 12, 2011, 1:41 pm
 wrote:

The trick with Phytoseilius is to monitor the spider mite population
closely and to introduce a proportionate number of predators
(Phytoseilius). If you put too many in they eat the rsm and then start
on one another. Too few and you fail to get effective control. The
'dead white bugs' the o/p saw were most likely the cast skins of
moulting aphids so a heavy infestation of rsm and aphids is suggested
as the culprits. As you advised - outside and treat with something
like Provado is likely to be the best approach at this late stage.

Rod