Preventing Sunburn on Apples

Discussion in 'Conversations Forum' started by Eric La Fountaine, Jan 17, 2005.

  1. Eric La Fountaine

    Eric La Fountaine Contributor Forums Moderator 10 Years

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  2. Ron B

    Ron B Paragon of Plants 10 Years

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    Result of overpruning?
     
  3. I heard from someone at HOS that they had to be careful about spraying trees in the daytime because of the water acting as a magnifying glass and burning the apples. Just a thought.
     
  4. Ron B

    Ron B Paragon of Plants 10 Years

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  5. mr.shep

    mr.shep Well-Known Member 10 Years

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    Watering foliage during hot days doesn't scorch it

    It surely can if there are salts in the water. Also, high levels
    of lime in the water and once allowed to dry in hot weather
    will burn foliage.

    I thought I had referenced the original article Preventing
    Sunburn on Apples
    in a former post of mine in this forum
    in regards to overhead watering but I have not found it.

    I think there are some interesting points brought out in
    the article. I like the whole idea of using an overhead
    watering system to ward off specific diseases and certain
    insects but once we initiate a program to water for long
    periods of the day we will be married to doing it. Years
    ago I proposed a ground and overhead watering system
    for Plums, Apples, some Citrus, Pears and Cherries to
    which my brethren in Fruit Trees could not see the
    economic importance of having a dual watering method
    until several years later. I agree with the premise in the
    article but I am at a loss to explain how the core temperature
    can prevent sun burning or sun scald of the skin of Apples.
    We grow Fujis here and sun scald is not prevalent even
    with ground based watering practices only. We do see
    some incidence of sun burning on Granny Smith's however
    and from what I've seen canopy management and the
    effect of over pruning does indeed play a role in how
    much sun burning we will see on Granny Smith Apples.
    I'll even take it a step further by stating that from our
    experience certain dwarfing rootstock have led to a
    higher frequency rate of the number of Apples in the
    outer portion of the tree facing the sun for the longer
    portions of the day can burn, as opposed to Granny
    Smith Apples grafted on standard rootstock will. I
    think we will find if we study it closer that where the
    sun burning has occurred we will likely find a higher
    degree of ethylene build up in the flesh tissue, right
    underneath the skin, depending on the variety of Apple
    as some Apples will scald easier than others will. If
    the skin is allowed to remain a relative, constant
    temperature then I believe the premise is correct in that
    we will have less incidence of sunburn no matter what
    rootstock we are using and how much intense sunlight
    we get. For the Apples that get tissue breakdown right
    under the discolored skin that used to be thought of as
    being a physiological disorder.

    What I especially like in the article is the effect of
    timing our waterings, not so much to save water
    as that notion has not been adequately estimated
    but was thrown in to help secure the funding of the
    study but if areas are using overhead watering from
    dawn to dusk then if we only water from noon to
    dusk to achieve maximum protection then we will
    have some water savings in certain areas of the
    Apple growing country but there was no mention
    of a ground based watering program to coincide
    with the overhead watering. Overhead watering
    alone will not leach the salts out of the soil in
    the root zone but can help yield a higher level
    of concentration of salt build up instead.

    The mist overhead waterings seems to work best
    on trellised Apples rather than standard row planted
    non trellised Apples.

    Jim
     
  6. Ron B

    Ron B Paragon of Plants 10 Years

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    Hi Jim

    If you look at the article I linked to it mentions salts and chlorine scorching foliage. The water is not causing the damage, these are. Water that does not contain them in sufficient amounts will not scorch.
     
  7. mr.shep

    mr.shep Well-Known Member 10 Years

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    I do not believe there was any mention of alkaline
    water as applied onto foliage and the effects thereof
    in the The Myth of Hot-Weather Watering article.
    I believe the chlorine and sodium mentioned were not
    derived, as referenced, from the water itself at all but
    from other ground based and foliar applied sources.
    All I did was point out that salts present in alkaline
    water can indeed help cause wet leaves to sunburn.
    Yes, we do have areas here that have alkaline water,
    even to the extent that rainfall in those areas can be
    saline to alkaline.

    I agree pure water will not cause a sun burning but
    elements intermixed in the water can scorch leaves.
    Even a topographically applied acid water can aid
    in the burning of leaves in hot sun and we've seen
    that happen on Conifers in the form of acid rain in
    warm weather conditions here as opposed to acid
    rain in cool weather. The generalization that wet
    leaves will not sunburn is not totally true as a result
    of naturally occurring, existing conditions in some
    areas here in California.

    My argument is not with you Ron. Many people
    never have had to deal with alkaline water to better
    know how it can adversely affect the leaves of
    various plants. A higher degree of sun burning is
    one of the more noticeable effects some nurseries
    and homeowners near here have had to learn to live
    with arising from overhead sprinkler irrigation.

    Jim
     
  8. Ron B

    Ron B Paragon of Plants 10 Years

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    Hi Jim

    The mythical magnifying glass effect was the idea first put forward here, which is what I was responding to.
     
  9. mr.shep

    mr.shep Well-Known Member 10 Years

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    Hi Ron:

    Yes, the so-called prism effect of the interaction
    of water, sunlight and leaf surfaces was the issue
    you responded to and the article was correct, for
    now, to call the leaf burn a myth based on what we
    know so far. I knew what you meant Ron.

    My objection was to the wet leaves will not sunburn
    as I've seen what can happen before and after and have
    helped work on solutions for people, around here and
    also around the central to mid-upper, Oregon coast on
    plantation grown Conifers.

    I agree with the salt issue in the article but no one
    wants to talk about topographical salts and lime build
    up on the leaves and how the interaction of water and
    direct sunlight can yield a scalding effect on leaves
    with the right temperate conditions.

    It was because of what happened to plots of fruit trees
    with overhead sprinkler irrigation only at a nearby
    UC Experimental Station is what led some of us to
    propose the dual watering methods (sprinklers and
    groundwater) for fruit trees and some Citrus back
    in the late 70's. It was the ground based salt build up
    is what lead to the eventual demise of the trees long
    since gone and removed and replanted with Kiwis
    back in the early 80's.

    Jim
     

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