We have been receiving calls regarding the practice of applying copper fungicide to freeze damaged palms. I have discussed this with Dr. Monica Elliott, the palm disease expert at the University of Florida. Here is what we know and our recommendations.

Our landscapes contain many species of tropical palms growing much further north than their native habitats. These palms are showing the affects of the recent cold weather, how much damage was done is impossible to tell at this time. Obvious cold damage symptoms are the brown fronds, but internal bud and trunk damage may not show up for months. Since hard freezes occur so infrequently and cannot be predicted it is hard to conduct research on the problem. There is no hard data that can predict damage based on temperature and duration like we have for other crops such as citrus. We do know that secondary plant pathogens often attack weakened palms through damaged tissue as the weather warms. These secondary pathogens are probably already present in low levels but don’t infect healthy tissue until they are damaged by the cold. Bacteria and fungal pathogens are the primary cause of these bud rots in cold damaged palms.

Bud drenches containing copper are recommended to help reduce these secondary pathogens from attacking damaged tissues. Copper is used because it has both bacterial and fungicidal properties. A second application 10 days later is recommended. No more than 2 applications of copper should be made due to the possibility of copper phytotoxicity. We cannot guarantee the health of the tree even after treatment.

The decision to treat cold damage palms should be based on visible damage and value to the owner. Palms with severe browning would be more likely to need treatment than those with just some tip burning. Since there is no way to predict disease initiation, one must decide if the treatment costs outweigh the possibility of losing the tree.

If you have any questions, contact Bug Master at 866-662-2847.

Written by:
Brian Combs, General Manager, M. Ag. CPH, CCA, CPO,
Certified Professional Horticulturist - Certified Consulting Arborist
Member of the American Society of Consulting Arborist