Root Aphids in A. sikokianum

[Jim McClements, Dover, DE z6]

A-Lers

There has been a recent discussion on Trillium-L about A. sikokianum, which 
included several references to the fact that many of us report that it is 
short-lived in our gardens. This is usually attributed to winter rot from exÎss 
moisture.

The posting that I copied below was a revelation to me and certainly 
introduces a new possible reason for the problem.

It's interesting that aphids are only mentioned fleetingly in the new editio=n 
of the Gusmans' book, and then only in reference to the foliage.

This is certainly worthy of discussion in this group. If you look at what 
John Gyer has posted on Florapix, I think you'll find it quite impressive, e=ven 
though Koch's postulates may not have been satisfied!
Jim



The advice others have given about Arisaema sikokianum seed production 
completely parallels what I have seen.  However, I'd like to add a comment=on the 
short life problem.

 

I have posted a recent picture on FloraPix Gallery that shows root aphids 
(probably an Anuraphis sp.) at work on the stem of a large A.sikokianum 
[http://florapix.nl/spgm-1.4.4/    scroll to Arisaema; scroll to S].=A0 These aphids 
start out as nymphs that settle on the fleshy stem just as it begins to shri=nk as 
its energy is drained into the fruit and tuber in the fall.  They work the=ir 
way down between the soil and the stem.  Eventually they find the tuber =where 
they can over-winter in a mass so thick that the tuber skin is not visible.=A0 I 
think they are tended by ants for their excretions, but I think the nymphal 
stages settle in as flying or at least airborne "larvae" from another plant 
where they summer.  I have seen the aphids attack A.triphyllum in equal fo=rce.

 

The aphids seem to have a waxy cuticle that can keep water soluble 
insecticides from reaching them.  An oil emulsion insecticide worked well =as a drench.  
Over-the-counter stuff from ORTHO (USA, I do not know what is used elsewhere=) 
should work if a bit of liquid detergent is used in the mix.  This probabl=y 
would have helped the water soluble insecticide I used, but I did not think =of 
it in time.

 

I suspect that heavy aphid attack can spread virus and greatly weaken the 
tuber.  The result could easily be winter rot or early death from disease.

 

John Gyer  Clarksboro  NJ  USA
====================================



Jim McClements
50 S. Prestwick Ct.
Dover, Delaware 19904, USA
Zone 7a
302-734-2836
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.science.uu.nl/pipermail/arisaema-l/attachments/20061025/7e6793e1/attachment.html