Huanglongbing (HLB), also known as citrus greening, is a serious bacterial disease that affects citrus in Florida, as well as many citrus production areas worldwide. The Asian citrus psyllid (ACP) is the insect responsible for spreading citrus greening. HLB is the most devastating citrus disease that threatens the citrus industry. There is no cure if a tree is infected. The likelihood of a tree infected with HLB is high and eventually unavoidable. Because more than 80% of citrus trees are infected with HLB, the new trees planted will become infected sooner or later. Citrus cultivation is more costly, time-consuming, and needs more inputs compared to before HLB presence. Now, the cost of growing citrus trees is almost three times more compared to the time we did not have greening in Florida. Although we do not have any cure for greening, many researchers and scientists around the States are looking for any possible cure to mitigate the negative effect of greening or finding new citrus varieties resistant to greening. At this time, it is necessary to update your knowledge about greening, whether you are a homeowner or a commercial citrus grower. In this article, we review some myths and facts about greening.
Homeowners cannot plant citrus trees in their backyards.
False. Homeowners in Florida are allowed to grow citrus trees in their backyards. The transport of backyard oranges, lemons, grapefruits, and kumquats is illegal in most of Southern California, which is under a citrus fruit and plant quarantine. Florida residents should be careful of transporting any citrus materials, especially infected trees to areas with low greening rates. Because greening can be spread by grafting, budding, or grafting is illegal for Florida homeowners. Only certified nurseries may graft/bud citrus trees from certified mother trees.
Other trees in my backyard can be infected by citrus greening because of my infected citrus tree.
Greening affects all citrus varieties and other plants in the Rutaceae family such as orange jasmine. If the tree belongs to a different family, there is no chance of infection by greening disease.
You can diagnose an infected tree by just finding the greening symptoms.
False. Although the citrus greening disease has typical symptoms, usually these symptoms are mistaken for other diseases or disorder’s symptoms. For example, differentiating between nutrient deficiencies and greening symptoms is difficult. One reason is that nutrient deficiency is one of the consequences of the greening disease.
Another challenge in diagnosing the greening disease is that a newly infected tree by greening does not show symptoms for several months. So, the infected tree can be the source of greening with no symptoms.
By using insecticide, I can control ACP and greening at the same time.
False. No chemical will provide complete protection. Even with chemical control methods, it is impossible to keep all ACP from gaining access to trees. As soon as a tree is infected with greening, applying pesticides to control ACP is not an effective method to cure the infected tree. Since there is no cure for greening yet, the only way to prevent spreading greening is through tree removal.
Tip for homeowners: There are limited chemicals available for homeowners. Foliar-applied chemicals available for homeowner ACP management include horticultural oil, malathion, and carbaryl (these are product ingredients, not brand names). Imidacloprid (product ingredient) is a soil-applied chemical. Organic options include horticultural mineral oil, neem oil, and kaolin clay. When applying any chemical, follow the label instructions.
You can’t replant a tree in the same spot where I had a diseased tree.
False. If you decide to remove the diseased citrus tree from your garden, remove all tree materials including tree stumps and roots from the spot because they can be a greening source for other trees. If you will replant a tree from a family other than Rutaceae in the same spot, then the disease will no longer infect your new tree.
For more information, please read UF/IFAS EDIS article.