10Apr2007 E-mail from Dr. John Strang, Fruit Specialist (who did his doctoral research in Oregon on fruit hardiness)

 We have had a series of devastating freezes over the last five days that have affected our Kentucky fruit crops as well as many of the surrounding states. Crop losses extend up to Michigan and down to Alabama. Many of thees freezes were advective freezes, where a cold polar air mass moved into our area with lots of wind. This type of freeze is very difficult to protect against. The critical temperatures for 90% kill for most of our tree fruit crop flowers at current stages of development is 24 to 25F.

We will discuss more of the specifics of the freezes at our Fruit Grower Meeting at Peak's Bramble Ridge Orchard on April 16th in Mt Sterling. Directions and phone numbers are listed in our February-March Fruit Facts newsletter. (Please note that the April 19th date that is also listed in the newsletter is not correct.)

It is important that when you talk to the news media about this that you AVOID telling them that the fruit crops were completely wiped out. This will increase the economic damage to our growers, because consumers won't visit their orchards and markets. Many growers will bring fruit in from other areas.

Fertilization

If bearing trees have not been fertilized, skip the fertilizer for this year, because this will produce too much growth. Apple growers may want to think about using Apogee at early petal fall, to reduce some of the shoot growth, reduce pruning needs for next season and to make shoots less susceptible to fire blight. A second application is usually necessary when growth again begins 1-4 weeks after the first application.

Newly planted and young fruit plantings should be fertilized. Special care should be given to newly planted plants (particularly grapes) that have been freeze injured or lost their leaves. They have lost most of the reserves in their roots and new growth will be weak. Keep these plants well watered, reduce weed competition at the plant bases and a little additional 20-20-20 or equivalent fertilizer wouldn't hurt.

The following are spray recommendations for commercial growers that do not have economic crops on their trees that would warrant a full season spray schedule, based on discussions with Dr. John Hartman and Dr. Ric Bessin.

Control Japanese beetles on any fruit crop if defoliation is becoming a problem.

Apples

Fire blight is a serious concern. Most of the bacteria were killed by the low temperatures, but our tree leaves and tissues have been ruptured and opened up by the freezing, providing an entry for fire blight bacteria. The tree cankers will still produce bacteria when the temperature gets above 65 F. Temperatures above 65F, particularly for several days with a rain or heavy dew could be prime periods for massive fire blight infections. A spray of streptomycin is warranted under these conditions. For the next several days the temperatures are predicted to be below 65 F.

Scab could still be a problem. Maintain a minimal spray schedule, particularly early in the season for scab, probably using Mancozeb if there is no crop. (There is a 77 PHI for Mancozeb) This material is less expensive.

Control Wooly Apple Aphid if noted. Control Rosy Apple Aphid if more than 10% of the terminal shoots have this insect.

Pears

Think about a streptomycin spray if the trees still have bloom, otherwise no sprays needed.

Peaches

Control Peach tree and Lesser peach tree borers with trunk sprays.

Plums

Control American plum borer with trunk sprays.

Strawberries

No sprays needed. If there are uninjured flowers (those with yellow as opposed to black centers), apply botrytis fruit rot sprays during bloom.

John StrangDept. of Horticulture N-318 Ag. Sci. Bldg. North University of Kentucky Lexington, KY 40546-0091 Phone: (859)257-5685 Fax: (859)257-2859 Email: jstrang@uky.edu