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EM's and dormant copper

Posted by David Doncaster 
EM's and dormant copper
April 18, 2018 10:43AM
Leaf curl on my peaches is the only place that I have not had success with EM's . This year I had to bite the bullet and hit them quite hard with copper . How soon can I start repopulating with EM's ?


David

Hillview Heritage Farm
Zone 5*in British Columbia



Edited 1 time(s). Last edit at 04/19/2018 09:46AM by Michael Phillips.
Re: EM's and copper
April 18, 2018 01:43PM
After spraying with copper (I use Cueva - Copper Octanoate) I wait until 2 inches of rain (copper labeling often says 1 inch but I like to error on the side of caution when I can) has fallen and I can no longer visibly see signs of the blue copper residue on the trees before I spray EM. . . Otherwise, I feel like it is merely a death sentence for those effective microbes. Exception being into newly opened blossoms which are not coated with copper and are virgin territory . . . in such a case go at those blooms with EM or any other bioantagonist you are working with, as needed.

For peach leaf curl, give it some time for the copper residue to do its work and to natually rinse off with the rains before recolonizing your tree canopies with EM.

Gopher Hill Apples
Zone 8 in California
Re: EM's and dormant copper
April 19, 2018 09:54AM
I agree that the timing between mineral fungicide application and holistic (with biological component) application addresses this to a degree. Leaf curl fungi utilize a bud-savvy overwintering strategy and thus effectiveness with dormant copper requires getting this application to exposed bud scales before tissue growth begins in earnest. This can be a micronized copper or copper soap product (which more often is reserved for use directly on foliage). Time passes; rains fall. The amount of rainfall may not be as pertinent, however, as where the copper lodges for the duration. Let's include twig lesions and bark crevices as part of this discussion now. Dormant copper is used as well to lessen brown rot pressure overwintering in twig lesions on stone fruits. Similarly, copper on apple and pear targets fire blight bacterium disseminating to bark crevices and (in warmer places) scab conidia overwintering in the bud scales as a result of late fall rains. A good copper formulation is going to hold fast in all such nooks and crannies. That's the point. More exposed tree surfaces and expanding foliage tissue -- along with the ground surface in the case of Spring1 -- is going to be the "other target" for colonizing with friendly organisms. That's the way to think about this.

It's tempting to change the title here to talk even more broadly about mineral fungicides and arboreal biology. The use of copper soap within the growing season on fire blight sensitive cultivars being one example. Especially sulfur as a scab management tool. Different targets, different surfaces. Microbes are dynamic, with populations constantly shifting in response to conditions and available nutrient resources. Anyhow, I did add "dormant" to your title, David, thinking it important to distinguish this as an early season answer.

Lost Nation Orchard
Zone 4b in New Hampshire
Re: EM's and dormant copper
April 19, 2018 03:35PM
I get asked this same question quite frequently and usually address it this way. Cueva is quite different from other copper formulations due to its low ppm (1.8% metallic copper equiv.) and the fatty acids present in the mix. Most copper compounds are many magnitudes higher than Cueva in terms of the a.i.% copper. Cuprofix for example is 40% metallic copper equiv). Time is surely a good measure of when the copper drops below any toxic level (to microbes), add in rain, heat, light, and plant absorption and I usually recommend 7-10 days in between a Cueva copper app and EM applications. Copper is an essential nutrient for plants and other living organisms, but the part I really like about Cueva are the fatty acids which can feed the microbes present and that get applied 7-10 days after. Not sure how long they last, but the low dose of Cu and the FAs are surely a good thing all the way around.

Mike Biltonen, Know Your Roots
Zone 5b in New York
Re: EM's and dormant copper
February 13, 2019 03:37PM
Did you guys notice any impact on pear trees after spraying Cueva? I'm going to try it for the first time this year but am always cautious when spraying fatty acids on the pears. Thanks!

Joanne Patton, Squire Oaks Farm
Zone 6A, Northern Virginia
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