[Community_garden] Rhubarb leaves

[yarrow at sfo.com]

At 3:15 PM -0500 9/24/07, Garth Taylor wrote:
>I read a little while ago that insect predators do not like the toxins in
>rhubarb leaves.
>
>If that's true, then it ought to be possible to make a tea of rhubarb leaves
>and spray it on plants to get rid of insects.
>
>Has anyone ever heard of this? Any ideas on dosage?


I haven't used it myself, but in the revised edition of Carrots Love 
Tomatoes, Louise Riotte says that a spray made from rhubarb leaves 
boiled in water can help prevent clubroot if "watered into drillings 
before sowing plants of the cabbage family, wallflowers, and other 
seeds"; also "useful on roses against greenfly and black spot." She 
doesn't mention dosage.

If I had a lot of rhubarb leaves and some identified pests that were 
not being controlled by predators, I'd try it out (on nonedible 
parts) and see if it made a difference in those pest populations 
without harming any predators.

But after a couple years of using as much homemade compost as I could 
produce on my community garden plot, with no other amendments or 
supplements (not even kelp or fermented comfrey tea this year), I 
have very few pests/diseases, and almost none that are worth going 
after. I do an occasional slug/snail patrol when I'm nurturing 
seedlings, I wash the ants off the artichokes before I pick them, I 
grow squash varieties that aren't bothered by squash bugs, and I try 
to ignore the rust on the raspberry leaves (I've been meaning to try 
cornmeal, but since the raz rust is all over the garden, I assume it 
would just get reinfected).