Pennsylvania Tree Fruit Phenology Report and Freeze Alert: April 7, 2026

We are currently running approximately one week ahead in phenology compared to last year across much of Pennsylvania. With sustained temperatures in the 60 to 80°F range over the past week, crop development has progressed very rapidly. Apple has advanced from green tip to open cluster, while peach has moved from calyx green to full bloom within a span of about 7 to 8 days.

Growing Degree Hours (GDH) data taken from NEWA, with a base 43 ˚F and a base 50 ˚F from 1/1/2026 – 4/6/2026.  

*Phenology measurements were taken on the morning of 6^th April

*Phenology measurements were taken on the morning of 6^th April

Freeze Alert for all regions in Pennsylvania

A freeze event is expected across Pennsylvania Tuesday night into Wednesday morning, with forecast temperatures dropping to 26°F in Adams and as low as 23°F in Bedford and Centre Counties. These temperatures are well below critical thresholds for many fruit crops, especially peaches, which are mostly at or near full bloom across Southern PA. There is also potential for damage in apples and pear, depending on location. Growers should consider activating frost protection measures where available and closely monitor site-specific conditions, as low-lying areas may experience even colder temperatures. After the freeze event, assess injury by cutting buds longitudinally and checking for browning or blackening of the pistils or ovules, which indicates tissue death. Avoid placing shoots in water to observe bloom, as damaged buds may still open but often fail to set fruit due to injury to reproductive tissues.

Critical Temperatures for frost damage on tree fruit 

This Penn State Extension article (Orchard Frost - Critical Temperatures for Various Fruits) lists the temperatures at which there is 10% and 90% bud kill after 30-minute exposure at each stage of development. 

With the upcoming cold weather, please keep in mind that these temperatures could be damaging to fruit buds.  

For more details, please visit this resource on critical temperatures for frost damage on fruit trees.

For more information on frost mitigation techniques and background information, this article on frost, critical temperatures, and frost protection can help. 

Special note on blossom thinning peaches with Accede^TM 

With parts of Adams and surrounding counties at full bloom, there is potential for mild to severe freeze damage depending on location. Assess injury by cutting buds longitudinally and checking for browning or blackening of the pistils or ovules, which indicates tissue death. Avoid placing shoots in water to observe bloom, as damaged buds may still open but often fail to set fruit due to injury to reproductive tissues.

Once you have evaluated the extent of freeze damage, adjust your Accede™ application rate accordingly. The labeled rate is 300–600 ppm (10–20 oz of product per 100 gallons per acre). A general use rate of 15 oz (≈450 ppm) per 100 gallons per acre is recommended under normal conditions. Reduce rates where bloom density is already below normal, and for young trees, sensitive varieties, or frost-damaged blocks.

Accede™ is labeled for use from pink through petal fall, so applications can still be made later in the week after damage assessment is complete.