Cold injury to plant tissue occurs when the water inside cells freezes. Cell membranes can no longer contain cell contents that begin to leak out, resulting in the death of the cell. The injury to maturing flower buds occurred over the past two weeks, causing significant damage to tree fruit throughout the Hudson Valley. Damage levels are site and variety dependent. In some cases, colder sites had delayed maturity with buds in a more protected state while trees in early ‘warmer’ sites were at greater risk.
The recent cold snap over the past two weeks of temperatures in the teens was unrelenting in its impact to the tree fruit industry throughout the eastern U.S. fruit-growing region. Damage to peaches has been seen into the mid-Atlantic this season. The varietal data we show here was taken from apple varieties on dwarfing rootstock of G11, B9 and Bud 9 at the Hudson Valley Research Lab orchard. This is a well drained site with alluvial soils, 400′ in elevation above sea level, providing eastern slope with early sun and cold air drainage to the Hudson River. The low temperature of 18.9F at 6AM on the morning of the 5th of April caused significant levels of injury to apple at our site. Yet, sites such as this represent a best case scenario related to orchard bud survival at this temperature.
This data represents a second assessment of the viability of the tree fruit crop after recent cold events during the week of April 12th, 2016 Flower buds from varieties across the orchard were removed from the branch and examined for freeze injury by slicing the developing bud longitudinally and looking for browning of the important flowering parts. Observations were made of the king and lateral flowers comprising the petals, pollen packets of the stamen, the stigma and style and developing overies that will become seeds. In most cases the injury was attributed to the stigma, stamen and pollen packets.
As we draw closer to bloom we may see temperatures drop again during the more vulnerable stages of flower development that further threaten our apple crop. We have already seen significant injury from the winter cold in February to peach, plum, apricot and nectarine throughout the Hudson Valley with only a few buds showing signs of development in the field.
It’s important to note that this type of assessment may be of some help in providing a grower with a basis for crop load reduction estimates when done on a specific farm. However, it should not be used to estimate regional crop losses or to predict generic thinning adjustments until fruit set can be established, carbohyrdate availability and weather are taken into account. Additionally, the impact on the viability of the fruit, such as fruit shape and ‘frost rings’ that may appear on pollinated and set fruit is very difficult to predict based on these assessments.
The bud damage chart from this week (April 12th) for the HVRL showed highest survival in Gala 88.7% >Fuji 80.7% >Red Delicious 78.0% >HoneyCrisp 72.0% >Empire 65.2% >NY-2 35.3% and NY-1 with only 54.7% sound flower buds.
The bud damage chart from last week for the HVRL showed highest survival in HoneyCrisp 81.6% >Gala 80.4% >Empire 77.8% >Fuji 65.3% >Red Delicious 61.0% >NY-1 54.7% and NY-2 with only 35.3% sound flower buds. Damage levels for a west Marlboro apple orchard showed Golden Delicious at 80% undamaged buds > Granny Smith 63% > Jonagold 31.6% > Gala 23.6% > Ginger Gold 12.3% and Early Fuji with 6% live buds.
Trials conducted by Dr. James Schuup on the use of micronutrients to support developing buds surviving the freeze event have been shown to be effective at promoting fruit development in some varieties. His summary article on the work he condcted while at the HVRL can be used to help make timely prebloom applications over the next few weeks. NY Fruit Quarterly, Vol. 9, N˚3, 2001, “Mineral Nutrition as a Factor in Cold Tolerance of Apple Trees”
