Apr 23, 2020

Pennsylvania apple, pear growers should check flowers for freeze damage

Similar to what we reported for peaches on April 21, weather stations at the Fruit Research and Extension Center in Adams County, Pennsylvania, showed that there was a strong temperature inversion about 5 a.m. with calm winds. The temperature at 837 feet elevation above sea level was 31°F, while at 810 feet elevation it was 28°F. At 730 ft. elevation we recorded 25°on a second weather station.

The differences in air temperature caused by the inversion resulted in a wide range of crop damage estimates. Melanie Schupp examined all the flowers on 20 spurs each of several varieties and recorded the elevation in several blocks. Fruitlet death was evident by browning of the ovules. The table shows that pome fruit at higher elevation had almost no injury, while those at lower elevation sustained significant damage. Some orchards in the region have reported no damage, while others are reporting severe damage.

We noted that Pink Lady and Regal 10-45 had less freeze damage in rows adjacent to Fuji which were nearly 100% dead. Another interesting observation was that almost all surviving flowers of Golden Delicious were the “king flowers” in the center of the cluster.

Growers are advised to cut some flowers and check for dark centers, paying attention to site elevation. The severity of injury can be very different at different locations of a given block, as is shown in the table with Honeycrisp and Gala apples, as well as Harrow Sweet pear. If severe damage is noted you should alert your crop insurance adjuster.

An orchard can sustain some freeze damage and still produce a crop. For example, if blossom density is good, a single fruit on every other spur may be adequate for a full crop. Developing fruits will need to be examined closely after they have grown a bit for loss of fruit quality due to russet and frost rings.

Orchard blocks with good bloom density and less than 50% flower damage may still need to be chemically thinned. These assessments should be done by petal fall so that a full range of thinning options are available for managing the crop if there is no damage.

Table 1. Freeze Injury to Apple and Pear Flowers by Variety and Site Elevation, April 17, 2020.