Hi Vincent,

I think you missed the first line of the last message where I say that this work was done with an airblast sprayer at 100 gal/A in my organic orchard. One must have a dedicated sprayer for organic. I can't use the handgun that block. Don't know what the fuss about handguns is about.

Actually, I've applied many of the organic coppers with an airblast and solo 451 mist blower and there was really no difference in performance in control or lack of phyto.

If we “must" continue this:

Our injury results seem to follow the acute toxicity/exposure phenomenon, 
whereby injury is higher when the concentration is higher not more dilute. This 
is not unlike when one is exposed to a toxin in water, air, or direct contact.
In orchard trials, reducing volume and maintaining coverage requires adequate 
spraying technology. i/e Not a gun.

What does your spray deposit look like in your trials?

Copper ions in large droplets (or high volume) react with leaf tissue until the 
water evaporates.

Small droplets evaporate quicker and reduce the toxicity.

This is something you can’t see if you paint the trees with a film of water 
using a gun.

When you attempt to reduce volume using the same gun, all you do is apply 
“less” droplets… But they are still slow drying big droplets.

So you are likely to conclude more concentrated material is more toxic… This is 
not surprising, right?

But not so relevant to orchard spraying with small droplets.

Conclusions drawn from trials performed with guns using large droplets are not 
always directly  applicable with airblast sprayers.

it’s Happy hour time = Drinking 2 beers or one glass of wine is the same for 
the alcool test, right?

But beer “rental” is shorter than for wine because that excess volume can’t 
stay in your bladder so long. So for a given metabolic rate I’m betting alcohol 
in your blood is higher with beer. i/e beer would get you hammered quicker than 
wine. I could be wrong, but at least it’s cheaper.

Point is: concentration vs volume is not so straightforward and spray 
application technology can greatly impact results.

caveat emptor.


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Kerik D.  Cox, Ph.D., Associate Professor
Plant Pathology and Plant-Microbe Biology Section
School of Integrative Plant Science
Cornell University
221 Barton Lab
630 West North Street           
Geneva, NY 14456 USA    

E-mail: kd...@cornell.edu
Faculty Office: (315) 787-2401
Fruit Pathology Lab: (315) 787-2402     
FAX: (315) 787-2389

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