In the Spring of 2002, over a week of summer like weather with highs climbing into the 80s and lows in the 60s caused rapid plant growth. We had cold wet rainy weather over the weekend with highs near 40 and lows near freezing. The weather cleared Monday evening resulting in wide spread frosts on Tuesday morning resulting in significant losses to all fruit crops. This was a classic radiation frost with clear skies and calm conditions. Reported lows reported for the region ranged from 29 to 20 F. Temperatures of 29 to 27 F were reported from the highest fruit sites while 22 to 20F were reported from the lower sites. Many good fruit sites reported temperatures of only 25 or 26.

Most stone fruit are at or near the bloom stage where freezing temperatures of 28 or 27 F will result in 10% loss and 24 F in 90 % loss. From the temperature range we expect to see 50% or more loss in most fruit plantings. With large fruited fruits (apples, peaches, plums and pears) this is not significant but for small-fruited fruit such as cherries, blueberries and grapes where many small fruit are needed for good yields this frost is a disaster. Also fruit on higher sites will be less damaged than those at lower sites

Blueberries were at early pink bud. At this bud stage temperatures of 24 F or colder are need to cause damage loss. Tuesday's frost caused damage to early varieties in cold sites I estimate a 25% loss to the crop. Blueberry growers whose fields lie in the coldest sites because that is where the best blueberry soils are reported 24 to 18 F and lower.

In strawberries new leaves were emerging. The buds are still in the crown. Freezing temperatures in the 20s should have caused little loss, since the flower buds are still below ground. Strawberry growers report about 10% loss to their strawberries. Strawberry fields that were under plastic were beginning to bloom. Freezing temperatures will result in losses to open flowers. Closed buds can take 27 to 22 F.

To assess frost damage in tree fruits we need to wait several hours after the frost for the tissues to thaw out. The dead tissue will then turn brown and we can tear or cut the flowers open to see if the pistil or ovary of the flower has turned brown or black. This means there will be no seed or fruit from that flower. The pictures that follow show dead pistils. All these pictures were taken April 23 or April 24.

Apricots were in the shuck after the petals had fallen off the flower. Freezing temperatures of 27 F will result in 10% loss and 24 F in 90 % loss. Since most apricots are grown in high sites there was only moderate damage from Tuesdays freeze. Damage in Apricots is related to site and variety. All or nothing were killed: 75% Loss.

Peaches were still in bloom. Tuesday's frost will significantly reduce the crop: 90% in Van Buren County.  Less (25-50%) in Berrien County which has more peach acreage and more good peach sites near Lake Michigan with good air drainage. Since peaches have large fruit only a small number of flowers are needed for a full crop, the loss of a large number of flowers does not mean the crop is severely impacted. This means we could still have an excellent peach crop. The peach bloosom on the left is alive while the one on the right was killed

Cherries were at or near blom. Temperatures of 28 F will result in 10% loss and 24 F in 90 % loss. Crop losses due to freezing temperatures are significant. Cherries are small fruit. Due to the small size of the fruit the number of fruit needs to be large to have a full crop.
Sweet cherries were still in bloom. Crop loss 75 % loss. In sweet cherries the story is similar to apricots, good sites and hardy varieties suffered little damage while lower sites were wiped out. The sweet cherry blossom on the left was kill on April 23,2002
Tart cherries were at white bud and scattered bloom had begun. Crop loss 50%. Losses are very site dependent. Some growers reported moderate losses, others reported little damage.

Plums were at full bloom. Crop losses due to freezing temperatures were significant and agaian site and variety dependent. Some growers reported heavy losses, other light losses.  At bloom temperatures of 28 F will result in 10% loss and 23 F in 90 % loss. Crop losses due to freezing temperatures on April 23, about 50%.

Apples were at pink and tight cluster. At tight cluster, temperatures of 27 F will result in 10% loss and 21 F in 90 % loss. At pink, when the petals are showing,   temperatures of 27 F will result in 10% loss and 21 F in 90 % loss. Most growers report light to moderat losses depending on the variety and site. Apple flowers are in clusters of 6. The center flower blooms first and has the potential to have the largest fruit. This flower is called the king bloom and is the most desirable flower to keep. The other flowers are called the side blooms and are ususlly thinned off to avoid a large crop of very small fruit. Unfortuanteily the king bloom is usually the first flower killed in a frost event. We have probably lost the king bloom and some of the side bloom so we still have fair crop potential at many sites. The picture on the left shows a dead apple flower, this was a king bloom. The picture on the right shows an apple flower cluster at pink.

Pears were at white bud.  It appears likely there was only light damage in pears.