Apple Re-Thinning Advisory for May 15, 2012
Posted: May 15, 2012
From May 6 to May 8, we measured three days of strong carbon deficits (see Carbon Deficit Model posted May 14). At the Adams County Orchard Meeting on May 9th, I recalled Ross Byer's research on the effect of shading on apple fruit drop, and suggested that growers wait, before re-thinning, to see if this didn't cause additional natural drop in their orchards. I think the effects of this are being expressed now. I'm seeing quite a strong drop, some from my thinners and some from the carbon deficit (see photo). This wave of drop is occurring about 10 days after the stress event, which indicates a probable causal relationship.
Some of this drop may be caused by previous chemical thinning also. Whatever the cause, growers are advised to check fruit set in their own orchards carefully before applying an additional thinner.