Tennessee Fruit Freeze Damage April 2007Dr. Dave Lockwood, UT Fruit Spec - 4-10-07

Severe damage to the 2007 fruit and nut crop occurred as a result of a combination of above average temperatures in March followed by severe cold temperatures over several recent nights. What is the status of the crop and what needs to be done now?

In most cases the fruit crop is gone and the nut crop has received serious damage. However, plasticulture strawberry growers who utilized a combination of row covers and overhead irrigation may have salvaged a partial crop. I was in a field yesterday where, although damage was present as evidenced by dead blooms and fruit and damaged foliage, there were many live blooms and fruit including a lot of ripe berries in one variety (Sweet Charllie).

Some apple varieties in higher elevations may come through with some fruit.Varieties like Rome and Golden Delicious that bloom late may have a partial crop on lateral blooms. In Johnson Co. last week, the king bloom of the blossom cluster was in the pink stage. I expect them to have been lost, however, lateral blooms may set a crop.

Some grape varieties may come back with a partial crop on secondary blooms.Again, this will be more prevalent in higher elevations where crop development was not as advanced as in other sites. The tendency to crop on secondary buds varies with the type of grapes being grown. French-American hybrids tend to be more fruitful on secondary buds than American bunch types.

With nut crops, new shoot growth and the catkins, male portion of the bloom where the pollen is located, has been killed. The potential for the crop has been greatly reduced. Plant stress may result in fewer female flowers and, of course, the lack of viable pollen.

What should be done now? It is too early to accurately assess damage so the best response is to wait for a while. There is no doubt about the status of the fruit crop loss with the exceptions mentioned above.However, it is premature to assess plant damage. Dieback of shoots and branches and in some cases, the entire aboveground portion of plants may have also occurred. For plants such as fig and oriental persimmons, dieback may extend to ground level. These plants will regrow from root suckers. However, since most oriental persimmons are grafted onto American persimmon, you will no longer have an Oriental persimmon. For adventurous people, regrafting the plant is an option. For others, if you do not want an American persimmon (some of them are very good), the rootstock needs to be dug up.

Don't fertilize or prune at this time. New growth in spring utilizes stored carbohydrates from last year (you may have heard someone say that all early growth of the plant and the crop is directly related to the health of the plant as it entered dormancy the previous fall). A portion of these stored food reserves have been utilized in the growth and crop development that was destroyed by the cold. Therefore, the plant is under stress. Regrowth will be related to the amount of stored reserves in the roots of plants. Fertilizing at this time will further increase the stress on plants. Damaged shoots and branches will, in most cases, have viable foliage. This leaf area is important to the plant in overcoming the stress that currently exists. Pruning would remove the valuable contribution that these leaves can make to the plant. Pruning should be done next winter unless branches and shoots have been killed, in which case their removal should be done now.

If there is a partial crop, a decision needs to be made regarding care.Assess the crop level over the next couple of weeks. If fruit is to be left on the plant, the level of pest control needs to be the same as for a full crop. Failure to control pests may result in a build-up of pests that will need to be overcome in future years. If some fruit remains on plants, realize that they are quite likely to have been damaged from the cold.This damage may range from surface scarring in which case the fruit may develop normally to injury that will result in the fruit dropping off the plant over the next few days or weeks. It may be better to defruit plants to avoid problems mentioned above if the level of cropping is not high enough to give a decent return. Pest control applications aimed at protecting the plant will still be needed. Control for trunk borers in stone fruit crops will be essential. Lesser borers in stone fruits will be a threat to branches above the level where trunk borers hit so some insecticide applications to the entire tree may be warranted. Japanese beetles need to be controlled as the leaf loss they can cause will further weaken already stressed plants. This is especially valid with young trees and vines.

Most areas of the state are already experiencing water deficits so supplemental watering is important, especially with young trees and vines where the root system may not be extensive.

Over the years that I have been in Tennessee, I have never seen a situation that exactly parallels what we are currently experiencing. Your observations and experiences will be valuable in anticipating courses of action if we should have this situation again in future years. Please let me know how growers in your area have fared.

Dr. Dave Lockwood, UT Fruit Spec - 4-10-07