Do not apply recovery techniques immediately after a freeze, cold-hardy citrus growers were advised after freezes hit their groves in December 2022 and January 2023. The best strategy is to wait to observe new growth until at least late spring, researcher Muhammad Shahid told the Georgia Citrus Association at its recent annual meeting. Shahid is a University of Florida Institute of Food and Agricultural Sciences assistant professor of horticulture at the North Florida Research and Education Center in Quincy.
FREEZE DAMAGE SYMPTOMS
Shahid cited early symptoms of freeze damage:
- Blackening and water soaking of new leaves and branches
- Hardening and yellowing of leaves
- Formation of greenish-brownish patches
- Leaves of old citrus trees become curly, stunted and yellow
- Fruit become hard due to the nucleation of water
Later symptoms of freeze damage include:
- Curling and browning of leaves, and eventually dying
- Quick drop of leaves and fruit
- Formation of micro-pits on fruit
- Rotting odor in the grove
- Rotting leaves and fruit attract ladybug beetles
- Dieback of new growth
Green tissue is a positive sign when determining the extent of damage after a freeze, Shahid said. On the other hand, dried leaves attached to the plant are a sign of severe damage due to freeze. New growth is not an indication that internal tissues are alive.
TREE RECOVERY TECHNIQUES
Shahid addressed fertilizer, biostimulants, plant protection, irrigation and pruning in the aftermath of a freeze:
Fertilizer and Biostimulants
- Do not apply any fertilizer until there is no new growth.
- Decide fertilizer rates based on degree of damage. Generally, fertilizer rates should be lower.
- Prefer balanced slow-release fertilizer.
- Lower rates and frequent application is the best strategy.
- The use of biostimulants such as humic acid, seaweed extract and fulvic acid is beneficial to improve cell repair.
- Due to new growth, there is more chance of aphids, whiteflies and leafminer attack following a freeze.
- Applications of fungicides should be planned.
- Removal of all fruit from freeze-damaged trees is important for quick recovery.
Irrigation after a freeze should be reduced. Excessive water in the roots can cause nutrients to move away from the plants. However, it’s not recommended to completely cut off the water supply.
- Delay pruning until late spring.
- Prune on living wood to ensure all damaged parts have been removed.
- If the tree has been damaged below the rootstock/scion union, it is best to re-graft the new scion on the rootstock instead of pruning.
Get more freeze recovery advice here.
Share this Post