SW Michigan Fruit Update

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Frost Freeze - April 26, 2006

Mark Longstroth, Bill Shane, Al Gaus

Freeze Nips Grapes

On April 26, a hard freeze hit SW Michigan. The Spring had gotten off to a quick start with warm temperatures for most of April. Development was about a week ahead of normal when a strong cold front moved through the area dropping temperatures 20 degrees. This was followed by a calm clear night and lows from 29 to 24 degrees. Tree fruit were blooming at that time and temperatures below 28 would cause damage. Tree fruit crops were all hurt by the freeze but the damage was less than you would expect for those crops considering that 25 F should have killed out most of the bloom. 

Juice grapes were hit very hard.  Grape shoots were one to two inches long and had several leaves out.  Almost all the grapes shoots were killed.  New grape shoots will grow but these new “secondary’ shoots are only half as fruitful as the dead primary shoots were.  This means that the grape crop has been reduced by half.  The same thing happened on April 23, 2002. There was no new growth on the vines for several weeks and I was asked if the grapes had been killed.   In 2002, the vines did grow and we had half a crop but we had real problems and grape growers struggled to harvest a decent crop.   While many fruit growers were relieved that the freeze was not worse, most grape growers are thinking about their options in 2006.  A more complete report appears below.

Below are the recorded temperatures for the Morening of April 26, 2006 from the new Weather for IPM decisions in Michigan site at http://www.enviroweather.msu.edu/home.asp. 

Tree Fruit

Tree fruits were damaged by the freeze Wednesday, April 26, 2006.  Bloom for most fruits were extensively damaged.  Higher fruit sites generally suffered less damage. Southern sites suffered more because they were further along and because colder low temperatures were to the south.  Large fruited types (i.e. apples, pears, and peaches) will suffer less loss because they need fewer fruit for a full crop compared to cherries. 

Apricots in the shuck were extensively damaged.  All but the best sites have little fruit left.

Peaches at petal fall.  Damage was severe in some sites. Bloom was very heavy so there is still a marketable crop in many orchards. 

Sweet cherries are in the shuck and were hurt hard by the freeze.  Growers with good sites report they still have a crop but lower orchards show extensive damage. 

Tart cherries: Montmorency cherries are at petal fall and were in full bloom during the freeze. The heavy bloom apparently protected most of the flowers because there was generally only light damage. Damage estimates are about 20% loss. The most common symptom was browning of the style where it joins the pistil. These flowers are unlikely to set fruit.  By Monday dead pistils were easy to find and identify. 

In Plums, Oriental plums were in the shuck and hit hard by the freeze.  European plums were at full bloom and suffered less damage. 

Apples are blooming.  Many open flowers were killed by Wednesday’s frost.  In many cases the king bloom and some of the side bloom are dead.  Early varieties in lower sites were hardest hit.  Later varieties were only lightly affected. 

Pears are at petal fall and were not severely affected by the frost. Growers need to protect against pear scab.

Small Fruit

Blueberries are at early pink bud and little damaged by the freeze.  Early varieties beginning to bloom were hurt but generally there are still lots of good flowers left. 

Grapes were the hardest hit by the freeze suffering severe damage. Juice grapes were more advanced than wine grapes and have more obvious damage.  Over large areas almost all the growing shoots were killed and growers report that many secondary buds had pushed and were killed also.  This freeze was similar to one in April 2002 that killed most of the shoots.  In 2002, several weeks passed before secondary bud growth was evident.  Initial estimates of primary bud mortality are about 25% in good sites up to 100% in many areas.  Secondary bud mortality is also high is some areas.  The potential juice grape crop has been reduced by at least 50% and probably more.  Wine grapes suffered much less damage.  A more accurate estimate can be made in about a month when the flower clusters in new replacement shoots are apparent. Growers with large areas of good growth should continue their disease control programs.  Growers with only scattered live shoots will want to wait until closer to bloom to decide in they should continue to protect the crop.  This decision needs to be made in time to allow the prebloom spray, which is very important.

Strawberries are beginning to bloom.  Growers protected against the freeze with sprinklers, but in some causes the flowers still froze.  This could be due to turning on the sprinkler system too late when temperatures are already near freezing or a simple failure of the system to protect down below the low 20s. 

Raspberries leaves are emerging on blackberry and summer raspberry canes.  Fall raspberry shoots are 4 to 6 inches tall.  The freeze did burn some new shoots on the ground and on the canes but the plants should recover with a good crop.