By: D. Scott NeSmith, Department of Horticulture, University of Georgia
Severe freeze events such as occurred in Georgia March 15-16, 2017 present multiple challenges to growers. The magnitude of the damage varies across locations, but overall in the state the damage is substantial. This is in fact the most severe crop damage I have seen in my 27 years working with blueberries in Georgia. The deep freeze, coupled with early crop advancement due to an unusually warm January and February, has caused in excess of a 50% loss, perhaps as much as 60 to 70% loss, of what stood to be one of our best crops ever; likely, approaching a Farm Gate value of $400 million if no freeze had occurred. The final tally of the damage is difficult to fully assess at this time, but will unfold in the next few weeks. However, growers are facing some difficult decisions at this time trying to go forward.
From observations of my own, and from reports of others, it appears the southern highbush crop was mostly spared for those growers that had adequate overhead sprinkler freeze protection. However, estimates are that only 50% ± 10% of the state’s southern highbush crop had adequate freeze protection. Growers with no overhead water, or with insufficient water capacity to protect from such a deep freeze, lost 90 to 100% of their southern highbush crop. Estimates are that highbush account for 50% ± 10% of our total blueberry acreage in the state, but likely accounts for 60% or more of our total crop value.
The state’s rabbiteye blueberry crop is largely not protected from freezes since it is a later season type. As a result, the 2017 freeze event caused heavy crop losses for rabbiteye growers. Again, from my own observations and reports from others, rabbiteye damage ranges from losses around 50 to 60% to nearly total crop loss (greater than 90%). There are some instances where damage in the 50 to 60% range might be able to salvage some crop using some of our recommendations for gibberellic acid applications from work we did years ago (NeSmith et al., 1995; NeSmith and Krewer, 1997; NeSmith et al., 1999; NeSmith and Krewer, 1999). But, at best that is likely to produce an inferior crop of fruit, resulting in a 30 to 50% crop that will ripen later and produce smaller berries. In more instances that not, I think rabbiteye damage will exceed 70 to 75%, and it is difficult to make a crop with that level of damage. I’m expecting over all, at best, we will have only 25 to 35% of a rabbiteye crop.
So, what do we do from here? Here are some recommendations from the blueberry team and from consultations with other regional experts.
- For southern highbush with adequate water for freeze protection, growers should proceed as normal. Since this is one of our earliest ripening crops ever, we can expect fruit harvest to begin in the next 10 to 14 days.
- For highbush without adequate frost protection damage is near Bushes have nearly 100% damaged fruit, and this can quickly become problematic for infection from diseases such as botrytis, which can hurt the crop long term. Growers are urged to spray recommended fungicides to help prevent infection immediately. These plants should also be heavily pruned to remove dead tissue and to promote new, healthy growth for next year. Growers should consider pruning highbush plants back to 3 to 4 ft in height, and the sooner the better. They need to take advantage of the “fruitless plants” growing time in April, May, and June to get added growth this season. Without these measure not only will growers lose this year’s crop, but they could likely see depressed yields next year as well.
- For rabbiteye fields that sustained injury in the 50 to 60% range, growers need to consider managing the remaining crop for disease pressure and they need to consider using gibberellic acid as a tool to help the wounded Realizing of course, that the freeze is in the marginal range for expected overwhelming success with the gibberellic acid.
- For rabbiteye fields that sustained injury of 70% or greater, growers need to manage disease as discussed above, and they need to consider heavily pruning back plants to insure plant health and improved yields next Rabbiteyes should be pruned back to a height of 4 to 5 ft. Again, time is of essence, and pruning should begin in the next 2 or 4 weeks at the latest to take advantage of the longer growing season of the “fruitless plants”.
NeSmith, D.S., G. Krewer, M. Rieger, and B. Mullinix. 1995. Gibberellic acid-induced fruit set of rabbiteye blueberry following freeze and physical injury. HortScience 30: 1241-1243.
NeSmith, D.S. and G. Krewer. 1997. Fruit set of eight rabbiteye blueberry (Vaccinium ashei Reade) cultivars in response to gibberellic acid application. Fruit Var. J. 51: 124-128.
NeSmith, D.S., G. Krewer, and O.M. Lindstrom. 1999. Fruit set of rabbiteye blueberry (Vaccinium ashei) after subfreezing temperatures. J. Amer. Soc. Hort. Sci. 124: 337-340.
NeSmith, D.S. and G. Krewer. 1999. Effect of bee pollination and GA3 on fruit size and maturity of three rabbiteye blueberry cultivars with similar fruit densities. HortScience. 34: 1106-1107.