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blackening leaves on pear

Posted by Peter Fisher 
blackening leaves on pear
May 22, 2013 05:28AM
I have two Comice pear trees where the leaves started blackening at the edges last week. I have had this problem before on other pears; the leaves blacken and curl and eventually the tree nearly defoliates. The trees do not die, and by the next spring will leaf out fine, though this process seems to stunt growth. I have not had any fruit yet (last year was the first fruiting year but I lost all pears to a late frost) so I can't tell what this fungus or whatever does to the fruit. I can't find any pcitures or descriptions that match this so am unable it to identify the cause. Whatever it is, sulfur is not an option for Comice for some reason. Anyone have experience with this or know what it is?

Turkey Creek Orchard
Solon, Iowa (zone 5A)
Re: blackening leaves on pear
May 28, 2013 03:03AM
i had the same problem with Comice pears . so ya , i sprayed some lime sulpher on the tree and i thought i killed it as all the leaves turned black and looked pretty ugly all summer .but this spring it came back just fine ..still the black edges on the leaves .not sure what it is .
Re: blackening leaves on pear
June 09, 2013 06:24PM
I'm thinking back on my history with Comice--there was one lone tree in a one acre block of Bartletts. It always looked unhealthy and vey rarely gave much fruit (but, as Hugh Williams said "If you only got one good pear a year it would be worth farming it, that's how good it tastes"). I now have a dozen trees which still don't produce much--yet. One fruit freak up here says our climate is too mild for Comice. But now that I read Paul and Peters comments--along with my 26 years of spraying sulphurs, I can see that the Comice did indeed have some blackening many years. This year with a nearly full blown Neem program I sprayed Lime /Sulphur twice--once before 1st Neem and once between first and second with no discernable burn--But (as reported in another forum) 2 days after 3rd Neem spray (12 days after L/S) 75% of my Comice pears (and Flemish Beauty and Orca) turned a scary black--some did not just one row away!! Gosh oh Gee--blame it on the Neem? It is an oil. I'm afraid this does not help solve the mystery of "Comice Burn" but I could not help but pipe in. There is a cadre of Comice growers up in Oregon whose fruit when it shows up in California is beautiful (but of course does not taste as good as my normally russety, blotchy, lumpy Comice). I have not made contact with these folks. They were not organic so maybe (likely) used chemical fungicides. The plot thickens and the mystery deepens.
Re: blackening leaves on pear
June 10, 2013 03:51AM
This is an interesting problem.

Potassium Deficiency perhaps?

Captured this text to share . . .

Potassium is generally not a common deficiency. Some mature orchards, particularly those on light, heavily leached granite or sandy soils, may benefit from potassium fertilizer. Young plantings in new soil do not usually need potassium fertilizer before cropping starts, but replant trees put into such soils which have not been fertilized with potassium, could be at risk.

In apple trees, the margins of older leaves of a potassium deficient apple tree turn yellow and then brown as potassium is a mobile element. The leaf edges become tattered, curl inwards and the leaf becomes boat-shaped.

In pear trees, the older basal leaves are also the first to show symptoms but the color of the scorched leaf edges is dark brown to black and the leaf is strongly rolled inward. Shoot growth is poor and fruit is small. Excess potassium can increase susceptibility to bitter pit.

Do you have any recent soil test results data to post up? pH, etc.

Gopher Hill Apples
Zone 8 in California
Re: blackening leaves on pear
June 10, 2013 04:48AM
The soil test is a few years old, but showed 4.3% om, 36 ppm P, 248 ppm K, 1.2 ppm Zn, and a pH of 6.8. This is bordeline high levels of potassium according to Iowa State soils lab. A leaf analysis of peaches (next row over in the same orchard) in 2011 showed the following ppm: P 2720, K 20600, Mg 5184, Ca 17720, Mn 36, Fe 121, Cu 29, Zn 90, and total N 2.2.
The provided no interpretation of the results, but from what I have tried to figure out, the magnesium was maybe a little high, P, K, Ca were OK.

The soil is a fairly heavy clay loam, and its on a good slope but these pears are near the bottom and the soil is definitely wetter there (this spring especially). I notice that a couple of peaches near the bottom are not doing well (peaches really don't like wet feet). Red Sensation and Concorde pears seem to be totally unaffected; they are a little further up the hill, and have dark green leaves. The trees that have the blackening problem (Crisp 'n' sweet as well as Comice) have lighter green leaves; don't know if this is just the variety or indicates a nutrition problem.

This is a new orchard, trees planted on CRP land in spring 2009. The same problem afflicted potomac pear trees 2 years in a row, (and they were even further up the hill, but also had light green leaves) and they just generally seemed sick, so I replaced them this spring.

Turkey Creek Orchard
Solon, Iowa (zone 5A)
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