John Strang, U.K. Extension Horticulturist and Matt Dixon, U.K. Ag. Meteorologist Compiled from Kentucky Fruit Facts March and April/May 2019 Newsletter

Growers are juggling jobs to keep up with the rapidly warming temperatures. Pears are blooming and apple bloom is beginning. Eastern tent caterpillar eggs are hatching, so watch for these on orchard trees. The U.K. Ag. Weather Center reports that the state averaged 9.08 inches of rainfall for the month of February, which makes this the second wettest February since data were recorded beginning in 1895. The wettest year was 1989 with 9.85 inches of rainfall. Our average rainfall for February is 3.67 inches.

I think that everyone can remember when the polar vortex slid into Kentucky at the end of January. Figure 1 shows the low temperature minimums for the first part of 2019. It felt cold, but fortunately we don't think that it was cold enough to cause injury to our fruit crops over most of the state. In the most northern counties where temperatures dropped below 0circF we would expect some damage to thornless blackberries and some injury to grapes, particularly those that are less hardy or stressed/weak. Fruit growers are concerned with the actual low temperature minimums which injure fruit plants and not with the wind chill which affects people and warm blooded animals.

We have noted a little more peach flower bud winter kill than expected at Princeton and in Lexington, however this still left plenty of surviving flower buds for a full crop. We are not positive as to when this damage occurred. The temperature dropped to 2.4 and 9.5°F at Lexington and Princeton respectively with the polar vortex on January 31, but buds were fully hardened at this point. We suspect that the damage occurred on February 9 when the temperature dropped to 15.6°F and 17.4°F at Lexington and Princeton respectively. This minimum temperature is not that low, but the temperature drop was proceeded by five days in the 60's and we reached 70°F in Lexington on one day and significant dehardening likely occurred. The other possible date for injury was March 5 when the temperature dropped to 9.7°F and 12.3°F in Lexington and Princeton. This however drop was proceeded by four days of cooler temperatures, but there were warmer temperatures prior to this. The freeze on the morning of April 1 likely killed more peach flower buds and flowers (Figure 2). This was more of an advective freeze with a cold air mass moving in from the north involving wind that mixed the air column making most frost protection techniques ineffective.

Figure 3 shows Growing Degree Day (GDD) accumulations for this season and several previous seasons including the 2007 Easter Freeze season. The faster growing degree days accumulate the more rapidly trees bud out and bloom. I consider 2018 to be an average season with respect to fruit harvest dates. So this year we are running slightly behind the 2018 season.

The U.K. Ag. Weather Center reports that we will probably be somewhat warmer than normal with normal rainfall for the next month. Our March precipitation was below normal, which is the first month with below normal precipitation since October 2018.