Leafhoppers and bienniel bearing

alan haighJuly 20, 2012

I have read that leafhopper damage does not significantly affect productivity of fruit trees but I'm beginning to doubt if this is true for trees grown with a very low spray program- especially certain varieties that are highly susceptible to significant infestation.

Here, Euro plums hardly grow during the summer months because of stunting when the white potato leafhoppers move in. It is interesting that J. plums are much less affected and are much more reliable croppers.

Apple varieties that are most susceptible to LH damage also seem to tend to be bienniel, such as Cox Orange and T. King.

Maybe this is all a coincidence, but I'm wondering if any of you have experience that would seem to support the conclusion that LHs can be a real problem in the orchard beyond just damaging and killing grafts and stunting the growth of establishing trees.

Leafhoppers, like aphids, mine for protean and pull a lot of carbohydrate out of the tree in ratio to their small size so they do more than just damage leaves and growing shoots. They also directly rob trees of a lot of energy.

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Interesting observation. Never before heard the two linked, in any context.

My first reaction is to disagree...the heavy alternate year bearing tends to take a while to recover...and recurring insect damage would cause continual drops in production, no?

So maybe a new thesis paper?

    Bookmark   July 21, 2012 at 6:18PM
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alan haigh

The real question is whether the apple trees determine flower set and the ultimate viability of those flowers based entirely on energy conditions in spring or if stored energy levels later in the year are also consequential.

I was at a lecture of a commercial grower in Santa Cruz CA about ten years ago who had sound reason to believe fruit set was determined by conditions of the entire previous season and not just the 2 weeks after pedal fall, but unfortunately I didn't take notes. All I remember is that at the time his evidence seemed almost conclusive to me.

I know another commercial grower who believes that cool wet weather shortly AFTER pedal fall has a strong reducing affect on crop load which my own experience seems to validate.

I know that with plums, a lot of flowers attended by lots of bees does not insure a good fruit set. I have often seen Long John plum in particular flower like mad and appear to set huge crops that end up dropping from the tree in mid-spring. Other plums nearby will set well when this one hardly bears many years. It always drops a much higher percentage of its early plums than other varieties ( incidentally, it is a real leaf hopper magnet).

When you google for info on alternate bearing the idea that much of the mechanisms remain a mystery is repeated often.

    Bookmark   July 22, 2012 at 8:26AM
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